mm/gup: handle huge pmd for follow_pmd_mask()

Replace pmd_trans_huge() with pmd_leaf() to also cover pmd_huge() as long
as enabled.

FOLL_TOUCH and FOLL_SPLIT_PMD only apply to THP, not yet huge.

Since now follow_trans_huge_pmd() can process hugetlb pages, renaming it
into follow_huge_pmd() to match what it does.  Move it into gup.c so not
depend on CONFIG_THP.

When at it, move the ctx->page_mask setup into follow_huge_pmd(), only set
it when the page is valid.  It was not a bug to set it before even if GUP
failed (page==NULL), because follow_page_mask() callers always ignores
page_mask if so.  But doing so makes the code cleaner.

[peterx@redhat.com: allow follow_pmd_mask() to take hugetlb tail pages]
Link: https://lkml.kernel.org/r/20240403013249.1418299-3-peterx@redhat.com
Link: https://lkml.kernel.org/r/20240327152332.950956-12-peterx@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Tested-by: Ryan Roberts <ryan.roberts@arm.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Andrew Jones <andrew.jones@linux.dev>
Cc: Aneesh Kumar K.V (IBM) <aneesh.kumar@kernel.org>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: James Houghton <jthoughton@google.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Kirill A. Shutemov <kirill@shutemov.name>
Cc: Lorenzo Stoakes <lstoakes@gmail.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: "Mike Rapoport (IBM)" <rppt@kernel.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Rik van Riel <riel@surriel.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Yang Shi <shy828301@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/gup.c b/mm/gup.c
index 2b06d59f2fa3b0c5c03b3709fbcef921132af28a..f7028c698c265dacdf3014a738d1c13242bf4f23 100644 (file)
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -580,6 +580,90 @@ static struct page *follow_huge_pud(struct vm_area_struct *vma,
 
        return page;
 }
+
+/* FOLL_FORCE can write to even unwritable PMDs in COW mappings. */
+static inline bool can_follow_write_pmd(pmd_t pmd, struct page *page,
+                                       struct vm_area_struct *vma,
+                                       unsigned int flags)
+{
+       /* If the pmd is writable, we can write to the page. */
+       if (pmd_write(pmd))
+               return true;
+
+       /* Maybe FOLL_FORCE is set to override it? */
+       if (!(flags & FOLL_FORCE))
+               return false;
+
+       /* But FOLL_FORCE has no effect on shared mappings */
+       if (vma->vm_flags & (VM_MAYSHARE | VM_SHARED))
+               return false;
+
+       /* ... or read-only private ones */
+       if (!(vma->vm_flags & VM_MAYWRITE))
+               return false;
+
+       /* ... or already writable ones that just need to take a write fault */
+       if (vma->vm_flags & VM_WRITE)
+               return false;
+
+       /*
+        * See can_change_pte_writable(): we broke COW and could map the page
+        * writable if we have an exclusive anonymous page ...
+        */
+       if (!page || !PageAnon(page) || !PageAnonExclusive(page))
+               return false;
+
+       /* ... and a write-fault isn't required for other reasons. */
+       if (vma_soft_dirty_enabled(vma) && !pmd_soft_dirty(pmd))
+               return false;
+       return !userfaultfd_huge_pmd_wp(vma, pmd);
+}
+
+static struct page *follow_huge_pmd(struct vm_area_struct *vma,
+                                   unsigned long addr, pmd_t *pmd,
+                                   unsigned int flags,
+                                   struct follow_page_context *ctx)
+{
+       struct mm_struct *mm = vma->vm_mm;
+       pmd_t pmdval = *pmd;
+       struct page *page;
+       int ret;
+
+       assert_spin_locked(pmd_lockptr(mm, pmd));
+
+       page = pmd_page(pmdval);
+       if ((flags & FOLL_WRITE) &&
+           !can_follow_write_pmd(pmdval, page, vma, flags))
+               return NULL;
+
+       /* Avoid dumping huge zero page */
+       if ((flags & FOLL_DUMP) && is_huge_zero_pmd(pmdval))
+               return ERR_PTR(-EFAULT);
+
+       if (pmd_protnone(*pmd) && !gup_can_follow_protnone(vma, flags))
+               return NULL;
+
+       if (!pmd_write(pmdval) && gup_must_unshare(vma, flags, page))
+               return ERR_PTR(-EMLINK);
+
+       VM_BUG_ON_PAGE((flags & FOLL_PIN) && PageAnon(page) &&
+                       !PageAnonExclusive(page), page);
+
+       ret = try_grab_page(page, flags);
+       if (ret)
+               return ERR_PTR(ret);
+
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+       if (pmd_trans_huge(pmdval) && (flags & FOLL_TOUCH))
+               touch_pmd(vma, addr, pmd, flags & FOLL_WRITE);
+#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
+
+       page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT;
+       ctx->page_mask = HPAGE_PMD_NR - 1;
+
+       return page;
+}
+
 #else  /* CONFIG_PGTABLE_HAS_HUGE_LEAVES */
 static struct page *follow_huge_pud(struct vm_area_struct *vma,
                                    unsigned long addr, pud_t *pudp,
@@ -587,6 +671,14 @@ static struct page *follow_huge_pud(struct vm_area_struct *vma,
 {
        return NULL;
 }
+
+static struct page *follow_huge_pmd(struct vm_area_struct *vma,
+                                   unsigned long addr, pmd_t *pmd,
+                                   unsigned int flags,
+                                   struct follow_page_context *ctx)
+{
+       return NULL;
+}
 #endif /* CONFIG_PGTABLE_HAS_HUGE_LEAVES */
 
 static int follow_pfn_pte(struct vm_area_struct *vma, unsigned long address,
@@ -784,31 +876,31 @@ static struct page *follow_pmd_mask(struct vm_area_struct *vma,
                        return page;
                return no_page_table(vma, flags, address);
        }
-       if (likely(!pmd_trans_huge(pmdval)))
+       if (likely(!pmd_leaf(pmdval)))
                return follow_page_pte(vma, address, pmd, flags, &ctx->pgmap);
 
        if (pmd_protnone(pmdval) && !gup_can_follow_protnone(vma, flags))
                return no_page_table(vma, flags, address);
 
        ptl = pmd_lock(mm, pmd);
-       if (unlikely(!pmd_present(*pmd))) {
+       pmdval = *pmd;
+       if (unlikely(!pmd_present(pmdval))) {
                spin_unlock(ptl);
                return no_page_table(vma, flags, address);
        }
-       if (unlikely(!pmd_trans_huge(*pmd))) {
+       if (unlikely(!pmd_leaf(pmdval))) {
                spin_unlock(ptl);
                return follow_page_pte(vma, address, pmd, flags, &ctx->pgmap);
        }
-       if (flags & FOLL_SPLIT_PMD) {
+       if (pmd_trans_huge(pmdval) && (flags & FOLL_SPLIT_PMD)) {
                spin_unlock(ptl);
                split_huge_pmd(vma, pmd, address);
                /* If pmd was left empty, stuff a page table in there quickly */
                return pte_alloc(mm, pmd) ? ERR_PTR(-ENOMEM) :
                        follow_page_pte(vma, address, pmd, flags, &ctx->pgmap);
        }
-       page = follow_trans_huge_pmd(vma, address, pmd, flags);
+       page = follow_huge_pmd(vma, address, pmd, flags, ctx);
        spin_unlock(ptl);
-       ctx->page_mask = HPAGE_PMD_NR - 1;
        return page;
 }
 

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 249318f367e4cc002044db2a8f09e37d113d89cc..157cee64850c808994975f836021f6e1bbfc42fd 100644 (file)
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1221,8 +1221,8 @@ vm_fault_t vmf_insert_pfn_pud(struct vm_fault *vmf, pfn_t pfn, bool write)
 EXPORT_SYMBOL_GPL(vmf_insert_pfn_pud);
 #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
 
-static void touch_pmd(struct vm_area_struct *vma, unsigned long addr,
-                     pmd_t *pmd, bool write)
+void touch_pmd(struct vm_area_struct *vma, unsigned long addr,
+              pmd_t *pmd, bool write)
 {
        pmd_t _pmd;
 
@@ -1577,88 +1577,6 @@ static inline bool can_change_pmd_writable(struct vm_area_struct *vma,
        return pmd_dirty(pmd);
 }
 
-/* FOLL_FORCE can write to even unwritable PMDs in COW mappings. */
-static inline bool can_follow_write_pmd(pmd_t pmd, struct page *page,
-                                       struct vm_area_struct *vma,
-                                       unsigned int flags)
-{
-       /* If the pmd is writable, we can write to the page. */
-       if (pmd_write(pmd))
-               return true;
-
-       /* Maybe FOLL_FORCE is set to override it? */
-       if (!(flags & FOLL_FORCE))
-               return false;
-
-       /* But FOLL_FORCE has no effect on shared mappings */
-       if (vma->vm_flags & (VM_MAYSHARE | VM_SHARED))
-               return false;
-
-       /* ... or read-only private ones */
-       if (!(vma->vm_flags & VM_MAYWRITE))
-               return false;
-
-       /* ... or already writable ones that just need to take a write fault */
-       if (vma->vm_flags & VM_WRITE)
-               return false;
-
-       /*
-        * See can_change_pte_writable(): we broke COW and could map the page
-        * writable if we have an exclusive anonymous page ...
-        */
-       if (!page || !PageAnon(page) || !PageAnonExclusive(page))
-               return false;
-
-       /* ... and a write-fault isn't required for other reasons. */
-       if (vma_soft_dirty_enabled(vma) && !pmd_soft_dirty(pmd))
-               return false;
-       return !userfaultfd_huge_pmd_wp(vma, pmd);
-}
-
-struct page *follow_trans_huge_pmd(struct vm_area_struct *vma,
-                                  unsigned long addr,
-                                  pmd_t *pmd,
-                                  unsigned int flags)
-{
-       struct mm_struct *mm = vma->vm_mm;
-       struct page *page;
-       int ret;
-
-       assert_spin_locked(pmd_lockptr(mm, pmd));
-
-       page = pmd_page(*pmd);
-       VM_BUG_ON_PAGE(!PageHead(page) && !is_zone_device_page(page), page);
-
-       if ((flags & FOLL_WRITE) &&
-           !can_follow_write_pmd(*pmd, page, vma, flags))
-               return NULL;
-
-       /* Avoid dumping huge zero page */
-       if ((flags & FOLL_DUMP) && is_huge_zero_pmd(*pmd))
-               return ERR_PTR(-EFAULT);
-
-       if (pmd_protnone(*pmd) && !gup_can_follow_protnone(vma, flags))
-               return NULL;
-
-       if (!pmd_write(*pmd) && gup_must_unshare(vma, flags, page))
-               return ERR_PTR(-EMLINK);
-
-       VM_BUG_ON_PAGE((flags & FOLL_PIN) && PageAnon(page) &&
-                       !PageAnonExclusive(page), page);
-
-       ret = try_grab_page(page, flags);
-       if (ret)
-               return ERR_PTR(ret);
-
-       if (flags & FOLL_TOUCH)
-               touch_pmd(vma, addr, pmd, flags & FOLL_WRITE);
-
-       page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT;
-       VM_BUG_ON_PAGE(!PageCompound(page) && !is_zone_device_page(page), page);
-
-       return page;
-}
-
 /* NUMA hinting page fault entry point for trans huge pmds */
 vm_fault_t do_huge_pmd_numa_page(struct vm_fault *vmf)
 {

diff --git a/mm/internal.h b/mm/internal.h
index d06072f06a8d798ed63a71c7fd54c21f7d4e8adb..5933a8e7d2dd58ae5bcea3daa625afe817502f06 100644 (file)
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -1114,9 +1114,8 @@ int __must_check try_grab_page(struct page *page, unsigned int flags);
  */
 void touch_pud(struct vm_area_struct *vma, unsigned long addr,
               pud_t *pud, bool write);
-struct page *follow_trans_huge_pmd(struct vm_area_struct *vma,
-                                  unsigned long addr, pmd_t *pmd,
-                                  unsigned int flags);
+void touch_pmd(struct vm_area_struct *vma, unsigned long addr,
+              pmd_t *pmd, bool write);
 
 /*
  * mm/mmap.c