mm: handle large folios in free_unref_folios()

Call folio_undo_large_rmappable() if needed.  free_unref_page_prepare()
destroys the ability to call folio_order(), so stash the order in
folio->private for the benefit of the second loop.

Link: https://lkml.kernel.org/r/20240227174254.710559-10-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm: use __page_cache_release() in folios_put()

Pass a pointer to the lruvec so we can take advantage of the
folio_lruvec_relock_irqsave().  Adjust the calling convention of
folio_lruvec_relock_irqsave() to suit and add a page_cache_release()
wrapper.

Link: https://lkml.kernel.org/r/20240227174254.710559-9-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm: use free_unref_folios() in put_pages_list()

Break up the list of folios into batches here so that the folios are more
likely to be cache hot when doing the rest of the processing.

Link: https://lkml.kernel.org/r/20240227174254.710559-8-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm: remove use of folio list from folios_put()

Instead of putting the interesting folios on a list, delete the
uninteresting one from the folio_batch.

Link: https://lkml.kernel.org/r/20240227174254.710559-7-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Ryan Roberts <ryan.roberts@arm.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Mel Gorman <mgorman@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

memcg: add mem_cgroup_uncharge_folios()

Almost identical to mem_cgroup_uncharge_list(), except it takes a
folio_batch instead of a list_head.

Link: https://lkml.kernel.org/r/20240227174254.710559-6-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Ryan Roberts <ryan.roberts@arm.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Mel Gorman <mgorman@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm: use folios_put() in __folio_batch_release()

There's no need to indirect through release_pages() and iterate over this
batch of folios an extra time; we can just use the batch that we have.

Link: https://lkml.kernel.org/r/20240227174254.710559-5-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Ryan Roberts <ryan.roberts@arm.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Mel Gorman <mgorman@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm: add free_unref_folios()

Iterate over a folio_batch rather than a linked list.  This is easier for
the CPU to prefetch and has a batch count naturally built in so we don't
need to track it.  Again, this lowers the maximum lock hold time from
32 folios to 15, but I do not expect this to have a significant effect.

Link: https://lkml.kernel.org/r/20240227174254.710559-4-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm: convert free_unref_page_list() to use folios

Most of its callees are not yet ready to accept a folio, but we know all
of the pages passed in are actually folios because they're linked through
->lru.

Link: https://lkml.kernel.org/r/20240227174254.710559-3-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Ryan Roberts <ryan.roberts@arm.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Mel Gorman <mgorman@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm: make folios_put() the basis of release_pages()

Patch series "Rearrange batched folio freeing", v3.

Other than the obvious "remove calls to compound_head" changes, the
fundamental belief here is that iterating a linked list is much slower
than iterating an array (5-15x slower in my testing).  There's also an
associated belief that since we iterate the batch of folios three times,
we do better when the array is small (ie 15 entries) than we do with a
batch that is hundreds of entries long, which only gives us the
opportunity for the first pages to fall out of cache by the time we get to
the end.

It is possible we should increase the size of folio_batch.  Hopefully the
bots let us know if this introduces any performance regressions.

This patch (of 3):

By making release_pages() call folios_put(), we can get rid of the calls
to compound_head() for the callers that already know they have folios.  We
can also get rid of the lock_batch tracking as we know the size of the
batch is limited by folio_batch.  This does reduce the maximum number of
pages for which the lruvec lock is held, from SWAP_CLUSTER_MAX (32) to
PAGEVEC_SIZE (15).  I do not expect this to make a significant difference,
but if it does, we can increase PAGEVEC_SIZE to 31.

Link: https://lkml.kernel.org/r/20240227174254.710559-1-willy@infradead.org
Link: https://lkml.kernel.org/r/20240227174254.710559-2-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/khugepaged: keep mm in mm_slot without MMF_DISABLE_THP check

Previously, we removed the mm from mm_slot and dropped mm_count
if the MMF_THP_DISABLE flag was set. However, we didn't re-add
the mm back after clearing the MMF_THP_DISABLE flag. Additionally,
We add a check for the MMF_THP_DISABLE flag in hugepage_vma_revalidate().

Link: https://lkml.kernel.org/r/20240227035135.54593-1-ioworker0@gmail.com
Fixes: 879c6000e191 ("mm/khugepaged: bypassing unnecessary scans with MMF_DISABLE_THP check")
Signed-off-by: Lance Yang <ioworker0@gmail.com>
Suggested-by: Yang Shi <shy828301@gmail.com>
Reviewed-by: Yang Shi <shy828301@gmail.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Zach O'Keefe <zokeefe@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

lib/test_vmalloc.c: use unsigned long constant

Use an unsigned long constant instead of an int constant and a cast.  This
fixes the checkpatch warning

WARNING: Unnecessary typecast of c90 int constant - '(unsigned long) 1' could be '1UL'
+     align = ((unsigned long) 1) << i;

Link: https://lkml.kernel.org/r/20240226191159.39509-4-martin@kaiser.cx
Signed-off-by: Martin Kaiser <martin@kaiser.cx>
Reviewed-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

lib/test_vmalloc.c: drop empty exit function

The module is never loaded successfully.  Therefore, it'll never be
unloaded and we can remove the exit function.

Link: https://lkml.kernel.org/r/20240226191159.39509-3-martin@kaiser.cx
Signed-off-by: Martin Kaiser <martin@kaiser.cx>
Reviewed-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

lib/test_vmalloc.c: fix typo in function name

Fix a typo and change the function name to init_test_configuration.  Both
caller and definition have the same typo, so the current code already
works.

Link: https://lkml.kernel.org/r/20240226191159.39509-2-martin@kaiser.cx
Signed-off-by: Martin Kaiser <martin@kaiser.cx>
Reviewed-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm: remove total_mapcount()

All users of total_mapcount() are gone, let's remove it.

Link: https://lkml.kernel.org/r/20240226141324.278526-3-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/memfd: refactor memfd_tag_pins() and memfd_wait_for_pins()

Patch series "mm: remove total_mapcount()", v2.

Let's remove the remaining user from mm/memfd.c so we can get rid of
total_mapcount().

This patch (of 2):

Both functions are the remaining users of total_mapcount().  Let's get rid
of the calls by converting the code to folios.

As it turns out, the code is unnecessarily complicated, especially:

1) We can query the number of pagecache references for a folio simply via
   folio_nr_pages(). This will handle other folio sizes in the future
   correctly.

2) The xas_set(xas, page->index + cache_count) call to increment the
   iterator for large folios is not required. Remove it.

Further, simplify the XA_CHECK_SCHED check, counting each entry exactly
once.

Memfd pages can be swapped out when using shmem; leave xa_is_value()
checks in place.

Link: https://lkml.kernel.org/r/20240226141324.278526-1-david@redhat.com
Link: https://lkml.kernel.org/r/20240226141324.278526-2-david@redhat.com
Co-developed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm: huge_memory: enable debugfs to split huge pages to any order

It is used to test split_huge_page_to_list_to_order for pagecache THPs.
Also add test cases for split_huge_page_to_list_to_order via both debugfs.

[ziy@nvidia.com: fix issue discovered with NFS]
Link: https://lkml.kernel.org/r/262E4DAA-4A78-4328-B745-1355AE356A07@nvidia.com
Link: https://lkml.kernel.org/r/20240226205534.1603748-9-zi.yan@sent.com
Signed-off-by: Zi Yan <ziy@nvidia.com>
Tested-by: Aishwarya TCV <aishwarya.tcv@arm.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Luis Chamberlain <mcgrof@kernel.org>
Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Cc: Michal Koutny <mkoutny@suse.com>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Yu Zhao <yuzhao@google.com>
Cc: Zach O'Keefe <zokeefe@google.com>
Cc: Aishwarya TCV <aishwarya.tcv@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm: thp: split huge page to any lower order pages

To split a THP to any lower order pages, we need to reform THPs on
subpages at given order and add page refcount based on the new page order.
Also we need to reinitialize page_deferred_list after removing the page
from the split_queue, otherwise a subsequent split will see list
corruption when checking the page_deferred_list again.

Note: Anonymous order-1 folio is not supported because _deferred_list,
which is used by partially mapped folios, is stored in subpage 2 and an
order-1 folio only has subpage 0 and 1.  File-backed order-1 folios are
fine, since they do not use _deferred_list.

[ziy@nvidia.com: fixup per discussion with Ryan]
Link: https://lkml.kernel.org/r/494F48CD-1F0F-4CAD-884E-6D48F40AF990@nvidia.com
Link: https://lkml.kernel.org/r/20240226205534.1603748-8-zi.yan@sent.com
Signed-off-by: Zi Yan <ziy@nvidia.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Luis Chamberlain <mcgrof@kernel.org>
Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Cc: Michal Koutny <mkoutny@suse.com>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Yu Zhao <yuzhao@google.com>
Cc: Zach O'Keefe <zokeefe@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm: page_owner: add support for splitting to any order in split page_owner

It adds a new_order parameter to set new page order in page owner.  It
prepares for upcoming changes to support split huge page to any lower
order.

Link: https://lkml.kernel.org/r/20240226205534.1603748-7-zi.yan@sent.com
Signed-off-by: Zi Yan <ziy@nvidia.com>
Cc: David Hildenbrand <david@redhat.com>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Luis Chamberlain <mcgrof@kernel.org>
Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Cc: Michal Koutny <mkoutny@suse.com>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Yu Zhao <yuzhao@google.com>
Cc: Zach O'Keefe <zokeefe@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm: memcg: make memcg huge page split support any order split

It sets memcg information for the pages after the split.  A new parameter
new_order is added to tell the order of subpages in the new page, always 0
for now.  It prepares for upcoming changes to support split huge page to
any lower order.

Link: https://lkml.kernel.org/r/20240226205534.1603748-6-zi.yan@sent.com
Signed-off-by: Zi Yan <ziy@nvidia.com>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Luis Chamberlain <mcgrof@kernel.org>
Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Cc: Michal Koutny <mkoutny@suse.com>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Yu Zhao <yuzhao@google.com>
Cc: Zach O'Keefe <zokeefe@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/page_owner: use order instead of nr in split_page_owner()

We do not have non power of two pages, using nr is error prone if nr is
not power-of-two.  Use page order instead.

Link: https://lkml.kernel.org/r/20240226205534.1603748-5-zi.yan@sent.com
Signed-off-by: Zi Yan <ziy@nvidia.com>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Luis Chamberlain <mcgrof@kernel.org>
Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Cc: Michal Koutny <mkoutny@suse.com>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Yu Zhao <yuzhao@google.com>
Cc: Zach O'Keefe <zokeefe@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/memcg: use order instead of nr in split_page_memcg()

We do not have non power of two pages, using nr is error prone if nr is
not power-of-two.  Use page order instead.

Link: https://lkml.kernel.org/r/20240226205534.1603748-4-zi.yan@sent.com
Signed-off-by: Zi Yan <ziy@nvidia.com>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Luis Chamberlain <mcgrof@kernel.org>
Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Cc: Michal Koutny <mkoutny@suse.com>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Yu Zhao <yuzhao@google.com>
Cc: Zach O'Keefe <zokeefe@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm: support order-1 folios in the page cache

Folios of order 1 have no space to store the deferred list.  This is not a
problem for the page cache as file-backed folios are never placed on the
deferred list.  All we need to do is prevent the core MM from touching the
deferred list for order 1 folios and remove the code which prevented us
from allocating order 1 folios.

Link: https://lore.kernel.org/linux-mm/90344ea7-4eec-47ee-5996-0c22f42d6a6a@google.com/
Link: https://lkml.kernel.org/r/20240226205534.1603748-3-zi.yan@sent.com
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Zi Yan <ziy@nvidia.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Luis Chamberlain <mcgrof@kernel.org>
Cc: Michal Koutny <mkoutny@suse.com>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Yu Zhao <yuzhao@google.com>
Cc: Zach O'Keefe <zokeefe@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/huge_memory: only split PMD mapping when necessary in unmap_folio()

Patch series "Split a folio to any lower order folios", v5.

File folio supports any order and multi-size THP is upstreamed[1], so both
file and anonymous folios can be >0 order.  Currently, split_huge_page()
only splits a huge page to order-0 pages, but splitting to orders higher
than 0 might better utilize large folios, if done properly.  In addition,
Large Block Sizes in XFS support would benefit from it during truncate[2].
This patchset adds support for splitting a large folio to any lower order
folios.

In addition to this implementation of split_huge_page_to_list_to_order(),
a possible optimization could be splitting a large folio to arbitrary
smaller folios instead of a single order.  As both Hugh and Ryan pointed
out [3,5] that split to a single order might not be optimal, an order-9
folio might be better split into 1 order-8, 1 order-7, ..., 1 order-1, and
2 order-0 folios, depending on subsequent folio operations.  Leave this as
future work.

[1] https://lore.kernel.org/all/20231207161211.2374093-1-ryan.roberts@arm.com/
[2] https://lore.kernel.org/linux-mm/20240226094936.2677493-1-kernel@pankajraghav.com/
[3] https://lore.kernel.org/linux-mm/9dd96da-efa2-5123-20d4-4992136ef3ad@google.com/
[4] https://lore.kernel.org/linux-mm/cbb1d6a0-66dd-47d0-8733-f836fe050374@arm.com/
[5] https://lore.kernel.org/linux-mm/20240213215520.1048625-1-zi.yan@sent.com/

This patch (of 8):

As multi-size THP support is added, not all THPs are PMD-mapped, thus
during a huge page split, there is no need to always split PMD mapping in
unmap_folio().  Make it conditional.

Link: https://lkml.kernel.org/r/20240226205534.1603748-1-zi.yan@sent.com
Link: https://lkml.kernel.org/r/20240226205534.1603748-2-zi.yan@sent.com
Signed-off-by: Zi Yan <ziy@nvidia.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Luis Chamberlain <mcgrof@kernel.org>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Michal Koutny <mkoutny@suse.com>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Yu Zhao <yuzhao@google.com>
Cc: Zach O'Keefe <zokeefe@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm: enumerate all gfp flags

Introduce GFP bits enumeration to let compiler track the number of used
bits (which depends on the config options) instead of hardcoding them.
That simplifies __GFP_BITS_SHIFT calculation.

Link: https://lkml.kernel.org/r/20240224015800.2569851-1-surenb@google.com
Suggested-by: Petr Tesařík <petr@tesarici.cz>
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Kent Overstreet <kent.overstreet@linux.dev>
Cc: Petr Tesarik <petr@tesarici.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm: madvise: pageout: ignore references rather than clearing young

While doing MADV_PAGEOUT, the current code will clear PTE young so that
vmscan won't read young flags to allow the reclamation of madvised folios
to go ahead.  It seems we can do it by directly ignoring references, thus
we can remove tlb flush in madvise and rmap overhead in vmscan.

Regarding the side effect, in the original code, if a parallel thread runs
side by side to access the madvised memory with the thread doing madvise,
folios will get a chance to be re-activated by vmscan (though the time gap
is actually quite small since checking PTEs is done immediately after
clearing PTEs young).  But with this patch, they will still be reclaimed.
But this behaviour doing PAGEOUT and doing access at the same time is
quite silly like DoS.  So probably, we don't need to care.  Or ignoring
the new access during the quite small time gap is even better.

For DAMON's DAMOS_PAGEOUT based on physical address region, we still keep
its behaviour as is since a physical address might be mapped by multiple
processes.  MADV_PAGEOUT based on virtual address is actually much more
aggressive on reclamation.  To untouch paddr's DAMOS_PAGEOUT, we simply
pass ignore_references as false in reclaim_pages().

A microbench as below has shown 6% decrement on the latency of
MADV_PAGEOUT,

 #define PGSIZE 4096
 main()
 {
  int i;
 #define SIZE 512*1024*1024
  volatile long *p = mmap(NULL, SIZE, PROT_READ | PROT_WRITE,
  MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);

  for (i = 0; i < SIZE/sizeof(long); i += PGSIZE / sizeof(long))
  p[i] =  0x11;

  madvise(p, SIZE, MADV_PAGEOUT);
 }

w/o patch                    w/ patch
root@10:~# time ./a.out      root@10:~# time ./a.out
real 0m49.634s            real   0m46.334s
user 0m0.637s             user   0m0.648s
sys 0m47.434s            sys    0m44.265s

Link: https://lkml.kernel.org/r/20240226005739.24350-1-21cnbao@gmail.com
Signed-off-by: Barry Song <v-songbaohua@oppo.com>
Acked-by: Minchan Kim <minchan@kernel.org>
Cc: SeongJae Park <sj@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

arm64/mm: improve comment in contpte_ptep_get_lockless()

Make clear the atmicity/consistency requirements of the API and how we
achieve them.

Link: https://lore.kernel.org/linux-mm/Zc-Tqqfksho3BHmU@arm.com/
Link: https://lkml.kernel.org/r/20240226120321.1055731-3-ryan.roberts@arm.com
Signed-off-by: Ryan Roberts <ryan.roberts@arm.com>
Acked-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

arm64/mm: export contpte symbols only to GPL users

Patch series "Address some contpte nits".

These 2 patches address some nits raised by Catalin late in the review cycle for
my contpte series [1].

[1] https://lore.kernel.org/linux-mm/20240215103205.2607016-1-ryan.roberts@arm.com/

This patch (of 2):

The contpte symbols must be exported since some of the public inline
ptep_* APIs are called from modules and these inlines now call the contpte
functions.  Originally they were exported as EXPORT_SYMBOL() for fear of
breaking out-of-tree modules.  But we subsequently concluded that
EXPORT_SYMBOL_GPL() should be safe since these functions are deeply core
mm routines, and any module operating at this level is not going to be
able to survive on EXPORT_SYMBOL alone.

Link: https://lkml.kernel.org/r/20240226120321.1055731-1-ryan.roberts@arm.com
Link: https://lore.kernel.org/linux-mm/f9fc2b31-11cb-4969-8961-9c89fea41b74@nvidia.com/
Link: https://lkml.kernel.org/r/20240226120321.1055731-2-ryan.roberts@arm.com
Signed-off-by: Ryan Roberts <ryan.roberts@arm.com>
Acked-by: David Hildenbrand <david@redhat.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Docs/mm/damon/design: remove the details for pageout as paddr doesn't use MADV_PAGEOUT

The doc needs a fix.  As only in the case of virtual address, we are
calling madvise() with MADV_PAGEOUT.  But in the case of physical address,
we are calling reclaim_pages() directly.  MADV_PAGEOUT on virtual address
is much more aggresive to reclaim memory compared to reclaim_pages() on
paddr region.  This patch removes the details so that the description can
apply to both cases.  And we don't need to couple with the implementation
details.

Link: https://lkml.kernel.org/r/20240224224751.4673-1-21cnbao@gmail.com
Signed-off-by: Barry Song <v-songbaohua@oppo.com>
Reviewed-by: SeongJae Park <sj@kernel.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

kasan: fix a2 allocation and remove explicit cast in atomic tests

Address the additional feedback since 4e76c8cc3378 kasan: add atomic tests
(""kasan: add atomic tests") by removing an explicit cast and fixing the
size as well as the check of the allocation of `a2`.

Link: https://lkml.kernel.org/r/20240224105414.211995-1-paul.heidekrueger@tum.de
Link: https://lore.kernel.org/all/20240131210041.686657-1-paul.heidekrueger@tum.de/T/#u
Fixes: 4e76c8cc3378 ("kasan: add atomic tests")
Signed-off-by: Paul Heidekrüger <paul.heidekrueger@tum.de>
Closes: https://bugzilla.kernel.org/show_bug.cgi?id=214055
Reviewed-by: Marco Elver <elver@google.com>
Tested-by: Marco Elver <elver@google.com>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

lib/stackdepot: off by one in depot_fetch_stack()

The stack_pools[] array has DEPOT_MAX_POOLS.  The "pools_num" tracks the
number of pools which are initialized.  See depot_init_pool() for more
details.

If pool_index == pools_num_cached, this will read one element beyond what
we want.  If not all the pools are initialized, then the pool will be
NULL, triggering a WARN(), and if they are all initialized it will read
one element beyond the end of the array.

Link: https://lkml.kernel.org/r/361ac881-60b7-471f-91e5-5bf8fe8042b2@moroto.mountain
Fixes: b29d31885814 ("lib/stackdepot: store free stack records in a freelist")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

zram: zcomp: remove zcomp_set_max_streams() declaration

The zcomp_set_max_streams() is removed from commit 43209ea2d17a
("zram: remove max_comp_streams internals"), remove the declaration.

Link: https://lkml.kernel.org/r/20240223035548.2591882-2-wangkefeng.wang@huawei.com
Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: Chengming Zhou <chengming.zhou@linux.dev>
Cc: Huacai Chen <chenhuacai@kernel.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Yosry Ahmed <yosryahmed@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm: update mark_victim tracepoints fields

The current implementation of the mark_victim tracepoint provides only the
process ID (pid) of the victim process.  This limitation poses challenges
for userspace tools requiring real-time OOM analysis and intervention.
Although this information is available from the kernel logs, it’s not
the appropriate format to provide OOM notifications.  In Android, BPF
programs are used with the mark_victim trace events to notify userspace of
an OOM kill.  For consistency, update the trace event to include the same
information about the OOMed victim as the kernel logs.

- UID
   In Android each installed application has a unique UID. Including
   the `uid` assists in correlating OOM events with specific apps.

- Process Name (comm)
   Enables identification of the affected process.

- OOM Score
  Will allow userspace to get additional insight of the relative kill
  priority of the OOM victim. In Android, the oom_score_adj is used to
  categorize app state (foreground, background, etc.), which aids in
  analyzing user-perceptible impacts of OOM events [1].

- Total VM, RSS Stats, and pgtables
  Amount of memory used by the victim that will, potentially, be freed up
  by killing it.

[1] https://cs.android.com/android/platform/superproject/main/+/246dc8fc95b6d93afcba5c6d6c133307abb3ac2e:frameworks/base/services/core/java/com/android/server/am/ProcessList.java;l=188-283
Signed-off-by: Carlos Galo <carlosgalo@google.com>
Reviewed-by: Steven Rostedt <rostedt@goodmis.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: "Masami Hiramatsu (Google)" <mhiramat@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

selftests: damon: add access_memory to .gitignore

This binary is missing in the .gitignore and stays as an untracked file.

Link: https://lore.kernel.org/r/20240214-damon_selftest_gitignore-v1-1-f517d0f9f783@gmail.com
Link: https://lkml.kernel.org/r/20240221211148.46522-3-sj@kernel.org
Signed-off-by: Javier Carrasco <javier.carrasco.cruz@gmail.com>
Singed-off-by: SeongJae Park <sj@kernel.org>
Reported-by: Bernd Edlinger <bernd.edlinger@hotmail.de>
Closes: https://lore.kernel.org/all/AS8P193MB1285C963658008F1B2702AF7E4792@AS8P193MB1285.EURP193.PROD.OUTLOOK.COM/
Reviewed-by: SeongJae Park <sj@kernel.org>
Cc: Vincenzo Mezzela <vincenzo.mezzela@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

selftest: damon: fix minor typos in test logs

Patch series "selftests/damon: misc fixes".

Misc fixes for DAMON selftets on behalf of the original authors.

This patch (of 2):

This patch resolves a spelling error in the test log, preventing potential
confusion.

It is submitted as part of my application to the "Linux Kernel Bug Fixing
Spring Unpaid 2024" mentorship program of the Linux Foundation.

Link: https://lore.kernel.org/r/20240204122523.14160-1-vincenzo.mezzela@gmail.com
Link: https://lkml.kernel.org/r/20240221211148.46522-2-sj@kernel.org
Signed-off-by: Vincenzo Mezzela <vincenzo.mezzela@gmail.com>
Signed-off-by: SeongJae Park <sj@kernel.org>
Reviewed-by: SeongJae Park <sj@kernel.org>
Cc: Bernd Edlinger <bernd.edlinger@hotmail.de>
Cc: Javier Carrasco <javier.carrasco.cruz@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

hugetlb: allow faults to be handled under the VMA lock

Hugetlb can now safely handle faults under the VMA lock, so allow it to do
so.

This patch may cause ltp hugemmap10 to "fail".  Hugemmap10 tests hugetlb
counters, and expects the counters to remain unchanged on failure to
handle a fault.

In hugetlb_no_page(), vmf_anon_prepare() may bailout with no anon_vma
under the VMA lock after allocating a folio for the hugepage.  In
free_huge_folio(), this folio is completely freed on bailout iff there is
a surplus of hugetlb pages.  This will remove a folio off the freelist and
decrement the number of hugepages while ltp expects these counters to
remain unchanged on failure.

Originally this could only happen due to OOM failures, but now it may also
occur after we allocate a hugetlb folio without a suitable anon_vma under
the VMA lock.  This should only happen for the first freshly allocated
hugepage in this vma.

Link: https://lkml.kernel.org/r/20240221234732.187629-6-vishal.moola@gmail.com
Signed-off-by: Vishal Moola (Oracle) <vishal.moola@gmail.com>
Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Muchun Song <muchun.song@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

hugetlb: use vmf_anon_prepare() instead of anon_vma_prepare()

hugetlb_no_page() and hugetlb_wp() call anon_vma_prepare().  In
preparation for hugetlb to safely handle faults under the VMA lock, use
vmf_anon_prepare() here instead.

Additionally, passing hugetlb_wp() the vm_fault struct from
hugetlb_fault() works toward cleaning up the hugetlb code and function
stack.

Link: https://lkml.kernel.org/r/20240221234732.187629-5-vishal.moola@gmail.com
Signed-off-by: Vishal Moola (Oracle) <vishal.moola@gmail.com>
Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Muchun Song <muchun.song@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

hugetlb: pass struct vm_fault through to hugetlb_handle_userfault()

Now that hugetlb_fault() has a struct vm_fault, have
hugetlb_handle_userfault() use it instead of creating one of its own.

This lets us reduce the number of arguments passed to
hugetlb_handle_userfault() from 7 to 3, cleaning up the code and stack.

Link: https://lkml.kernel.org/r/20240221234732.187629-4-vishal.moola@gmail.com
Signed-off-by: Vishal Moola (Oracle) <vishal.moola@gmail.com>
Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Muchun Song <muchun.song@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

hugetlb: move vm_fault declaration to the top of hugetlb_fault()

hugetlb_fault() currently defines a vm_fault to pass to the generic
handle_userfault() function.  We can move this definition to the top of
hugetlb_fault() so that it can be used throughout the rest of the hugetlb
fault path.

This will help cleanup a number of excess variables and function arguments
throughout the stack.  Also, since vm_fault already has space to store the
page offset, use that instead and get rid of idx.

Link: https://lkml.kernel.org/r/20240221234732.187629-3-vishal.moola@gmail.com
Signed-off-by: Vishal Moola (Oracle) <vishal.moola@gmail.com>
Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Muchun Song <muchun.song@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/memory: change vmf_anon_prepare() to be non-static

Patch series "Handle hugetlb faults under the VMA lock", v2.

It is generally safe to handle hugetlb faults under the VMA lock.  The
only time this is unsafe is when no anon_vma has been allocated to this
vma yet, so we can use vmf_anon_prepare() instead of anon_vma_prepare() to
bailout if necessary.  This should only happen for the first hugetlb page
in the vma.

Additionally, this patchset begins to use struct vm_fault within
hugetlb_fault().  This works towards cleaning up hugetlb code, and should
significantly reduce the number of arguments passed to functions.

The last patch in this series may cause ltp hugemmap10 to "fail".  This is
because vmf_anon_prepare() may bailout with no anon_vma under the VMA lock
after allocating a folio for the hugepage.  In free_huge_folio(), this
folio is completely freed on bailout iff there is a surplus of hugetlb
pages.  This will remove a folio off the freelist and decrement the number
of hugepages while ltp expects these counters to remain unchanged on
failure.  The rest of the ltp testcases pass.

This patch (of 2):

In order to handle hugetlb faults under the VMA lock, hugetlb can use
vmf_anon_prepare() to ensure we can safely prepare an anon_vma.  Change it
to be a non-static function so it can be used within hugetlb as well.

Link: https://lkml.kernel.org/r/20240221234732.187629-6-vishal.moola@gmail.com
Link: https://lkml.kernel.org/r/20240221234732.187629-2-vishal.moola@gmail.com
Signed-off-by: Vishal Moola (Oracle) <vishal.moola@gmail.com>
Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Muchun Song <muchun.song@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/page_alloc: make check_new_page() return bool

Make check_new_page() return bool like check_new_pages()

Link: https://lkml.kernel.org/r/20240222091932.54799-1-gehao@kylinos.cn
Signed-off-by: Hao Ge <gehao@kylinos.cn>
Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

x86/mm: always pass NULL as the first argument of switch_mm_irqs_off()

The first argument of switch_mm_irqs_off() is unused by the x86
implementation.  Make sure that x86 code never passes a non-NULL value to
make this clear.  Update the only non violating caller, switch_mm().

Link: https://lkml.kernel.org/r/20240222190911.1903054-2-yosryahmed@google.com
Signed-off-by: Yosry Ahmed <yosryahmed@google.com>
Suggested-by: Dave Hansen <dave.hansen@intel.com>
Acked-by: Dave Hansen <dave.hansen@intel.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov (AMD) <bp@alien8.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

x86/mm: further clarify switch_mm_irqs_off() documentation

Commit accf6b23d1e5a ("x86/mm: clarify "prev" usage in
switch_mm_irqs_off()") attempted to clarify x86's usage of the arguments
passed by generic code, specifically the "prev" argument the is unused by
x86.  However, it could have done a better job with the comment above
switch_mm_irqs_off().  Rewrite this comment according to Dave Hansen's
suggestion.

Link: https://lkml.kernel.org/r/20240222190911.1903054-1-yosryahmed@google.com
Fixes: 3cfd6625a6cf ("x86/mm: clarify "prev" usage in switch_mm_irqs_off()")
Signed-off-by: Yosry Ahmed <yosryahmed@google.com>
Suggested-by: Dave Hansen <dave.hansen@intel.com>
Acked-by: Dave Hansen <dave.hansen@intel.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov (AMD) <bp@alien8.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/util.c: add byte count to __vm_enough_memory failure warning

Commit 44b414c8715c5dcf53288 ("mm/util.c: add warning if
__vm_enough_memory fails") adds debug information which gives the process
id and executable name should __vm_enough_memory() fail.  Adding the
number of pages to the failure message would benefit application
developers and system administrators in debugging overambitious memory
requests by providing a point of reference to the amount of memory causing
__vm_enough_memory() to fail.

1. Set appropriate kernel tunable to reach code path for failure
   message:

# echo 2 > /proc/sys/vm/overcommit_memory

2. Test program to generate failure - requests 1 gibibyte per
   iteration:

#include <stdlib.h>
#include <stdio.h>

int main(int argc, char **argv) {
for(;;) {
if(malloc(1<<30) == NULL)
break;

printf("allocated 1 GiB\n");
}

return 0;
}

3. Output:

Before:

__vm_enough_memory: pid: 1218, comm: a.out, not enough memory
for the allocation

After:

__vm_enough_memory: pid: 1137, comm: a.out, bytes: 1073741824,
not enough memory for the allocation

Link: https://lkml.kernel.org/r/20240222194617.1255-1-mcassell411@gmail.com
Signed-off-by: Matthew Cassell <mcassell411@gmail.com>
Cc: David Hildenbrand <david@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

sched/numa, mm: do not try to migrate memory to memoryless nodes

Memoryless nodes do not have any memory to migrate to, so, as an
optimization, stop trying it.

Link: https://lkml.kernel.org/r/20240219041920.1183-1-byungchul@sk.com
Link: https://lkml.kernel.org/r/20240216111502.79759-1-byungchul@sk.com
Fixes: c574bbe91703 ("NUMA balancing: optimize page placement for memory tiering system")
Signed-off-by: Byungchul Park <byungchul@sk.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Reviewed-by: "Huang, Ying" <ying.huang@intel.com>
Reviewed-by: Phil Auld <pauld@redhat.com>
Reviewed-by: Davidlohr Bueso <dave@stgolabs.net>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Benjamin Segall <bsegall@google.com>
Cc: Daniel Bristot de Oliveira <bristot@redhat.com>
Cc: Dietmar Eggemann <dietmar.eggemann@arm.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Valentin Schneider <vschneid@redhat.com>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/zswap: change zswap_pool kref to percpu_ref

All zswap entries will take a reference of zswap_pool when zswap_store(),
and drop it when free.  Change it to use the percpu_ref is better for
scalability performance.

Although percpu_ref use a bit more memory which should be ok for our use
case, since we almost have only one zswap_pool to be using.  The
performance gain is for zswap_store/load hotpath.

Testing kernel build (32 threads) in tmpfs with memory.max=2GB.  (zswap
shrinker and writeback enabled with one 50GB swapfile, on a 128 CPUs
x86-64 machine, below is the average of 5 runs)

        mm-unstable  zswap-global-lru
real    63.20        63.12
user    1061.75      1062.95
sys     268.74       264.44

[chengming.zhou@linux.dev: fix zswap_pools_lock usages after changing to percpu_ref]
Link: https://lkml.kernel.org/r/20240228154954.3028626-1-chengming.zhou@linux.dev
Link: https://lkml.kernel.org/r/20240210-zswap-global-lru-v3-2-200495333595@bytedance.com
Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
Reviewed-by: Nhat Pham <nphamcs@gmail.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Yosry Ahmed <yosryahmed@google.com>
Cc: Chengming Zhou <chengming.zhou@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/zswap: global lru and shrinker shared by all zswap_pools

Patch series "mm/zswap: optimize for dynamic zswap_pools", v3.

Dynamic pool creation has been supported for a long time, which maybe not
used so much in practice.  But with the per-memcg lru merged, the current
structure of zswap_pool's lru and shrinker become less optimal.

In the current structure, each zswap_pool has its own lru, shrinker and
shrink_work, but only the latest zswap_pool will be the current used.

1. When memory has pressure, all shrinkers of zswap_pools will try to
   shrink its lru list, there is no order between them.

2. When zswap limit hit, only the last zswap_pool's shrink_work will
   try to shrink its own lru, which is inefficient.

A more natural way is to have a global zswap lru shared between all
zswap_pools, and so is the shrinker. The code becomes much simpler too.

Another optimization is changing zswap_pool kref to percpu_ref, which will
be taken reference by every zswap entry.  So the scalability is better.

Testing kernel build (32 threads) in tmpfs with memory.max=2GB.  (zswap
shrinker and writeback enabled with one 50GB swapfile, on a 128 CPUs
x86-64 machine, below is the average of 5 runs)

        mm-unstable  zswap-global-lru
real    63.20        63.12
user    1061.75      1062.95
sys     268.74       264.44

This patch (of 3):

Dynamic zswap_pool creation may create/reuse to have multiple zswap_pools
in a list, only the first will be current used.

Each zswap_pool has its own lru and shrinker, which is not necessary and
has its problem:

1. When memory has pressure, all shrinker of zswap_pools will
   try to shrink its own lru, there is no order between them.

2. When zswap limit hit, only the last zswap_pool's shrink_work
   will try to shrink its lru list. The rationale here was to
   try and empty the old pool first so that we can completely
   drop it. However, since we only support exclusive loads now,
   the LRU ordering should be entirely decided by the order of
   stores, so the oldest entries on the LRU will naturally be
   from the oldest pool.

Anyway, having a global lru and shrinker shared by all zswap_pools is
better and efficient.

Link: https://lkml.kernel.org/r/20240210-zswap-global-lru-v3-0-200495333595@bytedance.com
Link: https://lkml.kernel.org/r/20240210-zswap-global-lru-v3-1-200495333595@bytedance.com
Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
Acked-by: Yosry Ahmed <yosryahmed@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Nhat Pham <nphamcs@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

writeback: remove a use of write_cache_pages() from do_writepages()

Use the new writeback_iter() directly instead of indirecting through a
callback.

[hch@lst.de: ported to the while based iter style]
Link: https://lkml.kernel.org/r/20240215063649.2164017-15-hch@lst.de
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Dave Chinner <dchinner@redhat.com>
Cc: David Howells <dhowells@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

writeback: add a writeback iterator

Refactor the code left in write_cache_pages into an iterator that the file
system can call to get the next folio for a writeback operation:

struct folio *folio = NULL;

while ((folio = writeback_iter(mapping, wbc, folio, &error))) {
error = <do per-folio writeback>;
}

The twist here is that the error value is passed by reference, so that the
iterator can restore it when breaking out of the loop.

Handling of the magic AOP_WRITEPAGE_ACTIVATE value stays outside the
iterator and needs is just kept in the write_cache_pages legacy wrapper.
in preparation for eventually killing it off.

Heavily based on a for_each* based iterator from Matthew Wilcox.

Link: https://lkml.kernel.org/r/20240215063649.2164017-14-hch@lst.de
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Dave Chinner <dchinner@redhat.com>
Cc: David Howells <dhowells@redhat.com>
Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

writeback: move the folio_prepare_writeback loop out of write_cache_pages()

Move the loop for should-we-write-this-folio to writeback_get_folio.

[hch@lst.de: fold loop into existing helper instead of a separate one per Jan]
Link: https://lkml.kernel.org/r/20240215063649.2164017-13-hch@lst.de
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Acked-by: Dave Chinner <dchinner@redhat.com>
Cc: Christian Brauner <brauner@kernel.org>
Cc: David Howells <dhowells@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

writeback: use the folio_batch queue iterator

Instead of keeping our own local iterator variable, use the one just added
to folio_batch.

Link: https://lkml.kernel.org/r/20240215063649.2164017-12-hch@lst.de
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Acked-by: Dave Chinner <dchinner@redhat.com>
Cc: Christian Brauner <brauner@kernel.org>
Cc: David Howells <dhowells@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

pagevec: add ability to iterate a queue

Add a loop counter inside the folio_batch to let us iterate from 0-nr
instead of decrementing nr and treating the batch as a stack.  It would
generate some very weird and suboptimal I/O patterns for page writeback to
iterate over the batch as a stack.

Link: https://lkml.kernel.org/r/20240215063649.2164017-11-hch@lst.de
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Acked-by: Dave Chinner <dchinner@redhat.com>
Cc: Christian Brauner <brauner@kernel.org>
Cc: David Howells <dhowells@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

writeback: simplify the loops in write_cache_pages()

Collapse the two nested loops into one.  This is needed as a step towards
turning this into an iterator.

Note that this drops the "index <= end" check in the previous outer loop
and just relies on filemap_get_folios_tag() to return 0 entries when index
> end.  This actually has a subtle implication when end == -1 because then
the returned index will be -1 as well and thus if there is page present on
index -1, we could be looping indefinitely.  But as the comment in
filemap_get_folios_tag documents this as already broken anyway we should
not worry about it here either.  The fix for that would probably a change
to the filemap_get_folios_tag() calling convention.

[hch@lst.de: update the commit log per Jan]
Link: https://lkml.kernel.org/r/20240215063649.2164017-10-hch@lst.de
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Acked-by: Dave Chinner <dchinner@redhat.com>
Cc: Christian Brauner <brauner@kernel.org>
Cc: David Howells <dhowells@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

writeback: factor writeback_get_batch() out of write_cache_pages()

This simple helper will be the basis of the writeback iterator.  To make
this work, we need to remember the current index and end positions in
writeback_control.

[hch@lst.de: heavily rebased, add helpers to get the tag and end index, don't keep the end index in struct writeback_control]
Link: https://lkml.kernel.org/r/20240215063649.2164017-9-hch@lst.de
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Acked-by: Dave Chinner <dchinner@redhat.com>
Cc: Christian Brauner <brauner@kernel.org>
Cc: David Howells <dhowells@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

writeback: factor folio_prepare_writeback() out of write_cache_pages()

Reduce write_cache_pages() by about 30 lines; much of it is commentary,
but it all bundles nicely into an obvious function.

[hch@lst.de: rename should_writeback_folio to folio_prepare_writeback per Jan]
Link: https://lkml.kernel.org/r/20240215063649.2164017-8-hch@lst.de
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Acked-by: Dave Chinner <dchinner@redhat.com>
Cc: Christian Brauner <brauner@kernel.org>
Cc: David Howells <dhowells@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

writeback: rework the loop termination condition in write_cache_pages

Rework the way we deal with the cleanup after the writepage call.

First handle the magic AOP_WRITEPAGE_ACTIVATE separately from real error
returns to get it out of the way of the actual error handling path.

The split the handling on intgrity vs non-integrity branches first, and
return early using a goto for the non-ingegrity early loop condition to
remove the need for the done and done_index local variables, and for
assigning the error to ret when we can just return error directly.

Link: https://lkml.kernel.org/r/20240215063649.2164017-7-hch@lst.de
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Dave Chinner <dchinner@redhat.com>
Cc: David Howells <dhowells@redhat.com>
Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

writeback: only update ->writeback_index for range_cyclic writeback

mapping->writeback_index is only [1] used as the starting point for
range_cyclic writeback, so there is no point in updating it for other
types of writeback.

[1] except for btrfs_defrag_file which does really odd things with
mapping->writeback_index.  But btrfs doesn't use write_cache_pages at all,
so this isn't relevant here.

Link: https://lkml.kernel.org/r/20240215063649.2164017-6-hch@lst.de
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Acked-by: Dave Chinner <dchinner@redhat.com>
Cc: Christian Brauner <brauner@kernel.org>
Cc: David Howells <dhowells@redhat.com>
Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

writeback: also update wbc->nr_to_write on writeback failure

When exiting write_cache_pages early due to a non-integrity write failure,
wbc->nr_to_write currently doesn't account for the folio we just failed to
write.  This doesn't matter because the callers always ingore the value on
a failure, but moving the update to common code will allow to simplify the
code, so do it.

Link: https://lkml.kernel.org/r/20240215063649.2164017-5-hch@lst.de
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Acked-by: Dave Chinner <dchinner@redhat.com>
Cc: Christian Brauner <brauner@kernel.org>
Cc: David Howells <dhowells@redhat.com>
Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

writeback: fix done_index when hitting the wbc->nr_to_write

When write_cache_pages finishes writing out a folio, it fails to update
done_index to account for the number of pages in the folio just written.
That means when range_cyclic writeback is restarted, it will be restarted
at this folio instead of after it as it should.  Fix that by updating
done_index before breaking out of the loop.

Link: https://lkml.kernel.org/r/20240215063649.2164017-4-hch@lst.de
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Acked-by: Dave Chinner <dchinner@redhat.com>
Cc: Christian Brauner <brauner@kernel.org>
Cc: David Howells <dhowells@redhat.com>
Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

writeback: remove a duplicate prototype for tag_pages_for_writeback

[hch@lst.de: split from a larger patch]
Link: https://lkml.kernel.org/r/20240215063649.2164017-3-hch@lst.de
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Acked-by: Dave Chinner <dchinner@redhat.com>
Cc: Christian Brauner <brauner@kernel.org>
Cc: David Howells <dhowells@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

writeback: don't call mapping_set_error on AOP_WRITEPAGE_ACTIVATE

Patch series "convert write_cache_pages() to an iterator", v8.

This is an evolution of the series Matthew Wilcox originally sent in June
2023, which has changed quite a bit since and now has a while based
iterator.

This patch (of 14):

mapping_set_error should only be called on 0 returns (which it ignores) or
a negative error code.

writepage_cb ends up being able to call writepage_cb on the magic
AOP_WRITEPAGE_ACTIVATE return value from ->writepage which means success
but the caller needs to unlock the page.  Ignore that and just call
mapping_set_error on negative errors.

(no fixes tag as this goes back more than 20 years over various renames
and refactors so I've given up chasing down the original introduction)

Link: https://lkml.kernel.org/r/20240215063649.2164017-1-hch@lst.de
Link: https://lkml.kernel.org/r/20240215063649.2164017-2-hch@lst.de
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Cc: Christian Brauner <brauner@kernel.org>
Cc: David Howells <dhowells@redhat.com>
Cc: Dave Chinner <dchinner@redhat.com>
Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/page_alloc: make bad_range() return bool

bad_range() can return bool, so let us change it.

Link: https://lkml.kernel.org/r/20240221073227.276234-1-gehao@kylinos.cn
Signed-off-by: Hao Ge <gehao@kylinos.cn>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

madvise:madvise_cold_or_pageout_pte_range(): allow split while folio_estimated_sharers = 0

The purpose is stopping splitting large folios whose mapcount are 2 or
above.  Folios whose estimated_shares = 0 should be still perfect and even
better candidates than estimated_shares = 1.

Consider a pte-mapped large folio with 16 subpages, if we unmap 1-15, the
current code will split folios and reclaim them while madvise goes on this
folio; but if we unmap subpage 0, we will keep this folio and break.  This
is weird.

For pmd-mapped large folios, we can still use "= 1" as the condition as
anyway we have the entire map for it.  So this patch doesn't change the
condition for pmd-mapped large folios.  This also explains why we had been
using "= 1" for both pmd-mapped and pte-mapped large folios before commit
07e8c82b5eff ("madvise: convert madvise_cold_or_pageout_pte_range() to use
folios"), because in the past, we used the mapcount of the specific
subpage, since the subpage had pte present, its mapcount wouldn't be 0.

The problem can be quite easily reproduced by writing a small program,
unmapping the first subpage of a pte-mapped large folio vs.  unmapping
anyone other than the first subpage.

Link: https://lkml.kernel.org/r/20240221085036.105621-1-21cnbao@gmail.com
Fixes: 2f406263e3e9 ("madvise:madvise_cold_or_pageout_pte_range(): don't use mapcount() against large folio for sharing check")
Signed-off-by: Barry Song <v-songbaohua@oppo.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Vishal Moola (Oracle) <vishal.moola@gmail.com>
Cc: Yin Fengwei <fengwei.yin@intel.com>
Cc: Yu Zhao <yuzhao@google.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Yang Shi <shy828301@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/swapfile:__swap_duplicate: drop redundant WRITE_ONCE on swap_map for err cases

The code is quite hard to read, we are still writing swap_map after
errors happen. Though the written value is as before,

 has_cache = count & SWAP_HAS_CACHE;
 count &= ~SWAP_HAS_CACHE;
 [snipped]
 WRITE_ONCE(p->swap_map[offset], count | has_cache);

It would be better to entirely drop the WRITE_ONCE for both
performance and readability.

[akpm@linux-foundation.org: avoid using goto]
Link: https://lkml.kernel.org/r/20240221091028.123122-1-21cnbao@gmail.com
Signed-off-by: Barry Song <v-songbaohua@oppo.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

shmem: properly report quota mount options

Report quota options among the set of mount options. This allows proper
user visibility into whether quotas are enabled or not.

Link: https://lkml.kernel.org/r/20240129120131.21145-1-jack@suse.cz
Fixes: e09764cff44b ("shmem: quota support")
Signed-off-by: Jan Kara <jack@suse.cz>
Reviewed-by: Carlos Maiolino <cmaiolino@redhat.com>
Acked-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/compaction: optimize >0 order folio compaction with free page split.

During migration in a memory compaction, free pages are placed in an array
of page lists based on their order.  But the desired free page order
(i.e., the order of a source page) might not be always present, thus
leading to migration failures and premature compaction termination.  Split
a high order free pages when source migration page has a lower order to
increase migration successful rate.

Note: merging free pages when a migration fails and a lower order free
page is returned via compaction_free() is possible, but there is too much
work.  Since the free pages are not buddy pages, it is hard to identify
these free pages using existing PFN-based page merging algorithm.

Link: https://lkml.kernel.org/r/20240220183220.1451315-5-zi.yan@sent.com
Signed-off-by: Zi Yan <ziy@nvidia.com>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Tested-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Tested-by: Yu Zhao <yuzhao@google.com>
Cc: Adam Manzanares <a.manzanares@samsung.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Huang Ying <ying.huang@intel.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Kemeng Shi <shikemeng@huaweicloud.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Luis Chamberlain <mcgrof@kernel.org>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Vishal Moola (Oracle) <vishal.moola@gmail.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Yin Fengwei <fengwei.yin@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/compaction: add support for >0 order folio memory compaction.

Before last commit, memory compaction only migrates order-0 folios and
skips >0 order folios.  Last commit splits all >0 order folios during
compaction.  This commit migrates >0 order folios during compaction by
keeping isolated free pages at their original size without splitting them
into order-0 pages and using them directly during migration process.

What is different from the prior implementation:
1. All isolated free pages are kept in a NR_PAGE_ORDERS array of page
   lists, where each page list stores free pages in the same order.
2. All free pages are not post_alloc_hook() processed nor buddy pages,
   although their orders are stored in first page's private like buddy
   pages.
3. During migration, in new page allocation time (i.e., in
   compaction_alloc()), free pages are then processed by post_alloc_hook().
   When migration fails and a new page is returned (i.e., in
   compaction_free()), free pages are restored by reversing the
   post_alloc_hook() operations using newly added
   free_pages_prepare_fpi_none().

Step 3 is done for a latter optimization that splitting and/or merging
free pages during compaction becomes easier.

Note: without splitting free pages, compaction can end prematurely due to
migration will return -ENOMEM even if there is free pages.  This happens
when no order-0 free page exist and compaction_alloc() return NULL.

Link: https://lkml.kernel.org/r/20240220183220.1451315-4-zi.yan@sent.com
Signed-off-by: Zi Yan <ziy@nvidia.com>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Tested-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Tested-by: Yu Zhao <yuzhao@google.com>
Cc: Adam Manzanares <a.manzanares@samsung.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Huang Ying <ying.huang@intel.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Kemeng Shi <shikemeng@huaweicloud.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Luis Chamberlain <mcgrof@kernel.org>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Vishal Moola (Oracle) <vishal.moola@gmail.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Yin Fengwei <fengwei.yin@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/compaction: enable compacting >0 order folios.

migrate_pages() supports >0 order folio migration and during compaction,
even if compaction_alloc() cannot provide >0 order free pages,
migrate_pages() can split the source page and try to migrate the base
pages from the split.  It can be a baseline and start point for adding
support for compacting >0 order folios.

Link: https://lkml.kernel.org/r/20240220183220.1451315-3-zi.yan@sent.com
Signed-off-by: Zi Yan <ziy@nvidia.com>
Suggested-by: Huang Ying <ying.huang@intel.com>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Tested-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Tested-by: Yu Zhao <yuzhao@google.com>
Cc: Adam Manzanares <a.manzanares@samsung.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Kemeng Shi <shikemeng@huaweicloud.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Luis Chamberlain <mcgrof@kernel.org>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Vishal Moola (Oracle) <vishal.moola@gmail.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Yin Fengwei <fengwei.yin@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/page_alloc: remove unused fpi_flags in free_pages_prepare()

Patch series "Enable >0 order folio memory compaction", v7.

This patchset enables >0 order folio memory compaction, which is one of
the prerequisitions for large folio support[1].

I am aware of that split free pages is necessary for folio migration in
compaction, since if >0 order free pages are never split and no order-0
free page is scanned, compaction will end prematurely due to migration
returns -ENOMEM.  Free page split becomes a must instead of an
optimization.

lkp ncompare results (on a 8-CPU (Intel Xeon E5-2650 v4 @2.20GHz) 16G VM)
for default LRU (-no-mglru) and CONFIG_LRU_GEN are shown at the bottom,
copied from V3[4].  In sum, most of vm-scalability applications do not see
performance change, and the others see ~4% to ~26% performance boost under
default LRU and ~2% to ~6% performance boost under CONFIG_LRU_GEN.

Overview
===

To support >0 order folio compaction, the patchset changes how free pages
used for migration are kept during compaction.  Free pages used to be
split into order-0 pages that are post allocation processed (i.e.,
PageBuddy flag cleared, page order stored in page->private is zeroed, and
page reference is set to 1).  Now all free pages are kept in a
NR_PAGE_ORDER array of page lists based on their order without post
allocation process.  When migrate_pages() asks for a new page, one of the
free pages, based on the requested page order, is then processed and given
out.  And THP <2MB would need this feature.

[1] https://lore.kernel.org/linux-mm/f8d47176-03a8-99bf-a813-b5942830fd73@arm.com/
[2] https://lore.kernel.org/linux-mm/20231113170157.280181-1-zi.yan@sent.com/
[3] https://lore.kernel.org/linux-mm/20240123034636.1095672-1-zi.yan@sent.com/
[4] https://lore.kernel.org/linux-mm/20240202161554.565023-1-zi.yan@sent.com/
[5] https://lore.kernel.org/linux-mm/20240212163510.859822-1-zi.yan@sent.com/
[6] https://lore.kernel.org/linux-mm/20240214220420.1229173-1-zi.yan@sent.com/
[7] https://lore.kernel.org/linux-mm/20240216170432.1268753-1-zi.yan@sent.com/

This patch (of 4):

Commit 0a54864f8dfb ("kasan: remove PG_skip_kasan_poison flag") removes
the use of fpi_flags in should_skip_kasan_poison() and fpi_flags is only
passed to should_skip_kasan_poison() in free_pages_prepare().  Remove the
unused parameter.

Link: https://lkml.kernel.org/r/20240220183220.1451315-1-zi.yan@sent.com
Link: https://lkml.kernel.org/r/20240220183220.1451315-2-zi.yan@sent.com
Signed-off-by: Zi Yan <ziy@nvidia.com>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: David Hildenbrand <david@redhat.com>
Cc: Adam Manzanares <a.manzanares@samsung.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: "Huang, Ying" <ying.huang@intel.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Kemeng Shi <shikemeng@huaweicloud.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Luis Chamberlain <mcgrof@kernel.org>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Vishal Moola (Oracle) <vishal.moola@gmail.com>
Cc: Yin Fengwei <fengwei.yin@intel.com>
Cc: Yu Zhao <yuzhao@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

MAINTAINERS: add Chengming Zhou as a zswap reviewer

I have been actively contributing to zswap and reviewing zswap patches for
a while, and I am already getting CC'd on most of them.  So add myself as
a reviewer, will continue to work on it and help with the review process.

Link: https://lkml.kernel.org/r/20240220073851.865113-1-chengming.zhou@linux.dev
Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Yosry Ahmed <yosryahmed@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/zsmalloc: remove get_zspage_mapping()

Actually we seldom use the class_idx returned from get_zspage_mapping(),
only the zspage->fullness is useful, just use zspage->fullness to remove
this helper.

Note zspage->fullness is not stable outside pool->lock, remove redundant
"VM_BUG_ON(fullness != ZS_INUSE_RATIO_0)" in async_free_zspage() since we
already have the same VM_BUG_ON() in __free_zspage(), which is safe to
access zspage->fullness with pool->lock held.

Link: https://lkml.kernel.org/r/20240220-b4-zsmalloc-cleanup-v1-3-5c5ee4ccdd87@bytedance.com
Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Yosry Ahmed <yosryahmed@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/zsmalloc: remove_zspage() don't need fullness parameter

We must remove_zspage() from its current fullness list, then use
insert_zspage() to update its fullness and insert to new fullness list.
Obviously, remove_zspage() doesn't need the fullness parameter.

Link: https://lkml.kernel.org/r/20240220-b4-zsmalloc-cleanup-v1-2-5c5ee4ccdd87@bytedance.com
Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Yosry Ahmed <yosryahmed@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/zsmalloc: remove set_zspage_mapping()

Patch series "mm/zsmalloc: some cleanup for get/set_zspage_mapping()".

The discussion[1] with Sergey shows there are some cleanup works to do
in get/set_zspage_mapping():

- the fullness returned from get_zspage_mapping() is not stable outside
  pool->lock, this usage pattern is confusing, but should be ok in this
  free_zspage path.

- we seldom use the class_idx returned from get_zspage_mapping(), only
  free_zspage path use to get its class.

- set_zspage_mapping() always set the zspage->class, but it's never
  changed after zspage allocated.

[1] https://lore.kernel.org/all/a6c22e30-cf10-4122-91bc-ceb9fb57a5d6@bytedance.com/

This patch (of 3):

We only need to update zspage->fullness when insert_zspage(), since
zspage->class is never changed after allocated.

Link: https://lkml.kernel.org/r/20240220-b4-zsmalloc-cleanup-v1-0-5c5ee4ccdd87@bytedance.com
Link: https://lkml.kernel.org/r/20240220-b4-zsmalloc-cleanup-v1-1-5c5ee4ccdd87@bytedance.com
Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Yosry Ahmed <yosryahmed@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm: compaction: early termination in compact_nodes()

No need to continue try compact memory if pending fatal signal, allow loop
termination earlier in compact_nodes().

The existing fatal_signal_pending() check does make compact_zone()
break out of the while loop, but it still enters the next zone/next
nid, and some unnecessary functions(eg, lru_add_drain) are called.
There was no observable benefit from the new test, it is just found
from code inspection when refactoring compact_node().

Link: https://lkml.kernel.org/r/20240208022508.1771534-1-wangkefeng.wang@huawei.com
Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: David Hildenbrand <david@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm: zswap: increase reject_compress_poor but not reject_compress_fail if compression returns ENOSPC

We used to rely on the returned -ENOSPC of zpool_malloc() to increase
reject_compress_poor.  But the code wouldn't get to there after commit
744e1885922a ("crypto: scomp - fix req->dst buffer overflow") as the new
code will goto out immediately after the special compression case happens.
So there might be no longer a chance to execute zpool_malloc now.  We are
incorrectly increasing zswap_reject_compress_fail instead.  Thus, we need
to fix the counters handling right after compressions return ENOSPC.  This
patch also centralizes the counters handling for all of compress_poor,
compress_fail and alloc_fail.

Link: https://lkml.kernel.org/r/20240219211935.72394-1-21cnbao@gmail.com
Fixes: 744e1885922a ("crypto: scomp - fix req->dst buffer overflow")
Signed-off-by: Barry Song <v-songbaohua@oppo.com>
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>
Reviewed-by: Nhat Pham <nphamcs@gmail.com>
Acked-by: Yosry Ahmed <yosryahmed@google.com>
Reviewed-by: Chengming Zhou <zhouchengming@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/z3fold: fix the comment for __encode_handle()

The comment is confusing that Pool lock should be held as this function
accesses first_num above the __encode_handle() because first_num is the
element of z3fold_header which is protected by z3fold_header->page_lock.

I found the same comment for encode_handle() in zbud.c by accident ,Pool
lock should be held as this function accesses first|last_chunks, which is
the element of zbud_header and it does not have any lock, so pool lock
should be held.

Z3fold is based on zbud, maybe the comment come from zbud, but it was
wrong, so fix it.

Link: https://lkml.kernel.org/r/20240219024453.2240147-1-hezhongkun.hzk@bytedance.com
Signed-off-by: Zhongkun He <hezhongkun.hzk@bytedance.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Vitaly Wool <vitaly.wool@konsulko.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/zsmalloc: remove unused zspage->isolated

The zspage->isolated is not used anywhere, we don't need to maintain it,
which needs to hold the heavy pool lock to update it, so just remove it.

Link: https://lkml.kernel.org/r/20240219-b4-szmalloc-migrate-v1-3-34cd49c6545b@bytedance.com
Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Yosry Ahmed <yosryahmed@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/zsmalloc: remove migrate_write_lock_nested()

The migrate write lock is to protect the race between zspage migration and
zspage objects' map users.

We only need to lock out the map users of src zspage, not dst zspage,
which is safe to map by users concurrently, since we only need to do
obj_malloc() from dst zspage.

So we can remove the migrate_write_lock_nested() use case.

As we are here, cleanup the __zs_compact() by moving putback_zspage()
outside of migrate_write_unlock since we hold pool lock, no malloc or free
users can come in.

Link: https://lkml.kernel.org/r/20240219-b4-szmalloc-migrate-v1-2-34cd49c6545b@bytedance.com
Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Yosry Ahmed <yosryahmed@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/zsmalloc: fix migrate_write_lock() when !CONFIG_COMPACTION

Patch series "mm/zsmalloc: fix and optimize objects/page migration".

This series is to fix and optimize the zsmalloc objects/page migration.

This patch (of 3):

migrate_write_lock() is a empty function when !CONFIG_COMPACTION, in which
case zs_compact() can be triggered from shrinker reclaim context.  (Maybe
it's better to rename it to zs_shrink()?)

And zspage map object users rely on this migrate_read_lock() so object
won't be migrated elsewhere.

Fix it by always implementing the migrate_write_lock() related functions.

Link: https://lkml.kernel.org/r/20240219-b4-szmalloc-migrate-v1-0-34cd49c6545b@bytedance.com
Link: https://lkml.kernel.org/r/20240219-b4-szmalloc-migrate-v1-1-34cd49c6545b@bytedance.com
Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Yosry Ahmed <yosryahmed@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Docs/admin-guide/mm/damon/reclaim: document auto-tuning parameters

Update DAMON_RECLAIM usage document for the user/self feedback based
auto-tuning of the quota.

Link: https://lkml.kernel.org/r/20240219194431.159606-21-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/damon/reclaim: implement memory PSI-driven quota self-tuning

Support the PSI-driven quota self-tuning from DAMON_RECLAIM by introducing
yet another parameter, 'quota_mem_pressure_us'.  Users can set the desired
amount of memory pressure stall time per each quota reset interval using
the parameter.  Then DAMON_RECLAIM monitor the memory pressure stall time,
specifically system-wide memory 'some' PSI value that increased during the
given time interval, and self-tune the quota using the DAMOS core logic.

Link: https://lkml.kernel.org/r/20240219194431.159606-20-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/damon/reclaim: implement user-feedback driven quota auto-tuning

DAMOS supports user-feedback driven quota auto-tuning, but only DAMON
sysfs interface is using it.  Add support of the feature on DAMON_RECLAIM
by adding one more input parameter, namely 'quota_autotune_feedback', for
providing the user feedback to DAMON_RECLAIM.  It assumes the target value
of the feedback is 10,000.

Link: https://lkml.kernel.org/r/20240219194431.159606-19-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Docs/admin-guide/mm/damon/usage: document quota goal metric file

Update DAMON usage document for the quota goal target_metric file.

[sj@kernel.org: fix a typo on the auto-tuning design reference link]
Link: https://lkml.kernel.org/r/20240221170852.55529-3-sj@kernel.org
Link: https://lkml.kernel.org/r/20240219194431.159606-18-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Docs/ABI/damon: document quota goal metric file

Update DAMON ABI document for the quota goal target_metric file.

Link: https://lkml.kernel.org/r/20240219194431.159606-17-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Docs/mm/damon/design: document quota goal self-tuning

Update DAMON design doc to explain the quota goal self-tuning, which can
be used by setting the goal's metric to metrics that kernel can
self-retrieve.

Link: https://lkml.kernel.org/r/20240219194431.159606-16-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/damon/sysfs-schemes: support PSI-based quota auto-tune

Extend DAMON sysfs interface to support the PSI-based quota auto-tuning by
adding a new file, 'target_metric' under the quota goal directory.  Old
users don't get any behavioral changes since the default value of the
metric is 'user input'.

Link: https://lkml.kernel.org/r/20240219194431.159606-15-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/damon/core: implement PSI metric DAMOS quota goal

Extend DAMOS quota goal metric with system wide memory pressure stall
time.  Specifically, the system level 'some' PSI for memory is used.  The
target value can be set in microseconds.  DAMOS measures the increased
amount of the PSI metric in last quota_reset_interval and use the ratio of
it versus the user-specified target PSI value as the score for the
auto-tuning feedback loop.

Link: https://lkml.kernel.org/r/20240219194431.159606-14-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/damon/core: support multiple metrics for quota goal

DAMOS quota auto-tuning asks users to assess the current tuned quota and
provide the feedback in a manual and repeated way.  It allows users
generate the feedback from a source that the kernel cannot access, and
writing a script or a function for doing the manual and repeated feeding
is not a big deal.  However, additional works are additional works, and it
could be more efficient if DAMOS could do the fetch itself, especially in
case of DAMON sysfs interface use case, since it can avoid the context
switches between the user-space and the kernel-space, though the overhead
would be only trivial in most cases.  Also in many cases, feedbacks could
be made from kernel-accessible sources, such as PSI, CPU usage, etc.  Make
the quota goal to support multiple types of metrics including such ones.

Link: https://lkml.kernel.org/r/20240219194431.159606-13-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/damon/core: let goal specified with only target and current values

DAMOS quota auto-tuning feature let users to set the goal by providing a
function for getting the current score of the tuned quota.  It allows
flexible goal setup, but only simple user-set quota is currently being
used.  As a result, the only user of the DAMOS quota auto-tuning is using
a silly void pointer casting based score value passing function.  Simplify
the interface and the user code by letting user directly set the target
and the current value.

Link: https://lkml.kernel.org/r/20240219194431.159606-12-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/damon/core: remove ->goal field of damos_quota

DAMOS quota auto-tuning feature supports static signle goal and dynamic
multiple goals via DAMON kernel API, specifically via ->goal and ->goals
fields of damos_quota struct, respectively.  All in-tree DAMOS kernel API
users are using only the dynamic multiple goals now.  Remove the unsued
static single goal interface.

Link: https://lkml.kernel.org/r/20240219194431.159606-11-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/damon/sysfs: use only quota->goals

DAMON sysfs interface implements multiple quota auto-tuning goals on its
level since the DAMOS core logic was supporting only single goal.  Now the
core logic supports multiple goals on its level.  Update DAMON sysfs
interface to reuse the core logic and drop unnecessary duplicated multiple
goals implementation.

Link: https://lkml.kernel.org/r/20240219194431.159606-10-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/damon/core: add multiple goals per damos_quota and helpers for those

The feedback-driven DAMOS quota auto-tuning feature allows only single
goal to the DAMON kernel API users.  The API users could implement
multiple goals for the end-users on their level, and that's what DAMON
sysfs interface is doing.  More DAMON kernel API users such as
DAMON_RECLAIM would need to do similar work.  To reduce unnecessary future
duplciated efforts, support multiple goals from DAMOS core layer.  To make
the support in minimum non-destructive change, keep the old single goal
setup interface, and add multiple goals setup.  The single goal will
treated as one of the multiple goals, so old API users are not required to
make any change.

Link: https://lkml.kernel.org/r/20240219194431.159606-9-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/damon/core: split out quota goal related fields to a struct

'struct damos_quota' is not small now.  Split out fields for quota goal to
a separate struct for easier reading.

Link: https://lkml.kernel.org/r/20240219194431.159606-8-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/damon: move comments and fields for damos-quota-prioritization to the end

The comments and definition of 'struct damos_quota' lists a few fields for
effective quota generation first, fields for regions prioritization under
the quota, and then remaining fields for effective quota generation.
Readers' should unnecesssarily switch their context in the middle.  List
all the fields for the effective quota first, and then fields for the
prioritization for making it easier to read.

Link: https://lkml.kernel.org/r/20240219194431.159606-7-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Docs/admin-guide/mm/damon/usage: document effective_bytes file

Update DAMON usage document for the effective quota file of the DAMON
sysfs interface.

Link: https://lkml.kernel.org/r/20240219194431.159606-6-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Docs/ABI/damon: document effective_bytes sysfs file

Update the DAMON ABI doc for the effective_bytes sysfs file and the
kdamond state file input command for updating the content of the file.

Link: https://lkml.kernel.org/r/20240219194431.159606-5-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/damon/sysfs: implement a kdamond command for updating schemes' effective quotas

Implement yet another kdamond 'state' file input command, namely
'update_schemes_effective_quotas'.  If it is written, the
'effective_bytes' files of the kdamond will be updated to provide the
current effective size quota of each scheme in bytes.

Link: https://lkml.kernel.org/r/20240219194431.159606-4-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/damon/sysfs-schemes: implement quota effective_bytes file

DAMON sysfs interface allows users to set two types of quotas, namely time
quota and size quota.  DAMOS converts time quota to a size quota and use
smaller one among the resulting two size quotas.  The resulting effective
size quota can be helpful for debugging and analysis, but not exposed to
the user.  The recently added feedback-driven quota auto-tuning is making
it even more mysterious.

Implement a DAMON sysfs interface read-only empty file, namely
'effective_bytes', under the quota goal DAMON sysfs directory.  It will be
extended to expose the effective quota to the end user.

Link: https://lkml.kernel.org/r/20240219194431.159606-3-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/damon/core: set damos_quota->esz as public field and document

Patch series "mm/damon: let DAMOS feeds and tame/auto-tune itself".

The Aim-oriented Feedback-driven DAMOS Aggressiveness Auto-tuning
patchset[1] which has merged since commit 9294a037c015 ("mm/damon/core:
implement goal-oriented feedback-driven quota auto-tuning") made the
mechanism and the policy separated.  That is, users can set a part of
DAMOS control policies without a deep understanding of the mechanism but
just their demands such as SLA.

However, users are still required to do some additional work of manually
collecting their target metric and feeding it to DAMOS.  In the case of
end-users who use DAMON sysfs interface, the context switches between
user-space and kernel-space could also make it inefficient.  The overhead
is supposed to be only trivial in common cases, though.  Meanwhile, in
simple use cases, the target metric could be common system metrics that
the kernel can efficiently self-retrieve, such as memory pressure stall
time (PSI).

Extend DAMOS quota auto-tuning to support multiple types of metrics
including the DAMOS self-retrievable ones, and add support for memory
pressure stall time metric.  Different types of metrics can be supported
in future.  The auto-tuning capability is currently supported for only
users of DAMOS kernel API and DAMON sysfs interface.  Extend the support
to DAMON_RECLAIM.

Patches Sequence
================

First five patches are for helping debugging and fine-tuning existing
quota control features.  The first one (patch 1) exposes the effective
quota that is made with given user inputs to DAMOS kernel API users and
kernel-doc documents.  Following four patches implement (patches 1, 2 and
3) and document (patches 4 and 5) a new DAMON sysfs file that exposes the
value.

Following six patches cleanup and simplify the existing DAMOS quota
auto-tuning code by improving layout of comments and data structures
(patches 6 and 7), supporting common use cases, namely multiple goals
(patches 8, 9 and 10), and simplifying the interface (patch 11).

Then six patches for the main purpose of this patchset follow.  The first
three changes extend the core logic for various target metrics (patch 12),
implement memory pressure stall time-based target metric support (patch
13), and update DAMON sysfs interface to support the new target metric
(patch 14).  Then, documentation updates for the features on design (patch
15), ABI (patch 16), and usage (patch 17) follow.

Last three patches add auto-tuning support on DAMON_RECLAIM.  The patches
implement DAMON_RECLAIM parameters for user-feedback driven quota
auto-tuning (patch 18), memory pressure stall time-driven quota
self-tuning (patch 19), and finally update the DAMON_RECLAIM usage
document for the new parameters (patch 20).

[1] https://lore.kernel.org/all/20231130023652.50284-1-sj@kernel.org/

This patch (of 20):

DAMOS allow users to specify the quota as they want in multiple ways
including time quota, size quota, and feedback-based auto-tuning.  DAMOS
makes one effective quota out of the inputs and use it at the end.
Knowing the current effective quota helps understanding DAMOS' internal
mechanism and fine-tuning quotas.  DAMON kernel API users can get the
information from ->esz field of damos_quota struct, but the field is
marked as private purpose, and not kernel-doc documented.  Make it public
and document.

Link: https://lkml.kernel.org/r/20240219194431.159606-1-sj@kernel.org
Link: https://lkml.kernel.org/r/20240219194431.159606-2-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/khugepaged: bypassing unnecessary scans with MMF_DISABLE_THP check

khugepaged scans the entire address space in the background for each
given mm, looking for opportunities to merge sequences of basic pages
into huge pages.  However, when an mm is inserted to the mm_slots list,
and the MMF_DISABLE_THP flag is set later, this scanning process
becomes unnecessary for that mm and can be skipped to avoid redundant
operations, especially in scenarios with a large address space.

On an Intel Core i5 CPU, the time taken by khugepaged to scan the
address space of the process, which has been set with the
MMF_DISABLE_THP flag after being added to the mm_slots list, is as
follows (shorter is better):

VMA Count |   Old   |   New   |  Change
---------------------------------------
    50    |   23us  |    9us  |  -60.9%
   100    |   32us  |    9us  |  -71.9%
   200    |   44us  |    9us  |  -79.5%
   400    |   75us  |    9us  |  -88.0%
   800    |   98us  |    9us  |  -90.8%

Once the count of VMAs for the process exceeds page_to_scan, khugepaged
needs to wait for scan_sleep_millisecs ms before scanning the next
process.  IMO, unnecessary scans could actually be skipped with a very
inexpensive mm->flags check in this case.

This commit introduces a check before each scanning process to test the
MMF_DISABLE_THP flag for the given mm; if the flag is set, the scanning
process is bypassed, thereby improving the efficiency of khugepaged.

This optimization is not a correctness issue but rather an enhancement
to save expensive checks on each VMA when userspace cannot prctl itself
before spawning into the new process.

On some servers within our company, we deploy a daemon responsible for
monitoring and updating local applications.  Some applications prefer
not to use THP, so the daemon calls prctl to disable THP before
fork/exec.  Conversely, for other applications, the daemon calls prctl
to enable THP before fork/exec.

Ideally, the daemon should invoke prctl after the fork, but its current
implementation follows the described approach.  In the Go standard
library, there is no direct encapsulation of the fork system call;
instead, fork and execve are combined into one through
syscall.ForkExec.

Link: https://lkml.kernel.org/r/20240129054551.57728-1-ioworker0@gmail.com
Signed-off-by: Lance Yang <ioworker0@gmail.com>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Zach O'Keefe <zokeefe@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

MAINTAINERS: update mm and memcg entries

Add F: lines for memory management and memory cgroup include files.

Link: https://lkml.kernel.org/r/20240208055727.142387-1-rppt@kernel.org
Signed-off-by: Mike Rapoport (IBM) <rppt@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>