mm: introduce vma_pgtable_walk_{begin|end}()

Introduce per-vma begin()/end() helpers for pgtable walks.  This is a
preparation work to merge hugetlb pgtable walkers with generic mm.

The helpers need to be called before and after a pgtable walk, will start
to be needed if the pgtable walker code supports hugetlb pages.  It's a
hook point for any type of VMA, but for now only hugetlb uses it to
stablize the pgtable pages from getting away (due to possible pmd
unsharing).

Link: https://lkml.kernel.org/r/20240327152332.950956-5-peterx@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Christoph Hellwig <hch@infradead.org>
Reviewed-by: Muchun Song <muchun.song@linux.dev>
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: David Hildenbrand <david@redhat.com>
Cc: James Houghton <jthoughton@google.com>
Cc: Jason Gunthorpe <jgg@nvidia.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: 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/include/linux/mm.h b/include/linux/mm.h
index 00a46a5d5c9d6d7389c8e305617f6e83121e7979..3dda0dbcae14490e019824b0042f2dcd969d7ff2 100644 (file)
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -4230,4 +4230,7 @@ static inline bool pfn_is_unaccepted_memory(unsigned long pfn)
        return range_contains_unaccepted_memory(paddr, paddr + PAGE_SIZE);
 }
 
+void vma_pgtable_walk_begin(struct vm_area_struct *vma);
+void vma_pgtable_walk_end(struct vm_area_struct *vma);
+
 #endif /* _LINUX_MM_H */

diff --git a/mm/memory.c b/mm/memory.c
index 62ee4a15092ae011e594492ff1db1acb15c080b2..0b92336bcebde1a15c8dabf459245e6f08ba1603 100644 (file)
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -6378,3 +6378,15 @@ void ptlock_free(struct ptdesc *ptdesc)
        kmem_cache_free(page_ptl_cachep, ptdesc->ptl);
 }
 #endif
+
+void vma_pgtable_walk_begin(struct vm_area_struct *vma)
+{
+       if (is_vm_hugetlb_page(vma))
+               hugetlb_vma_lock_read(vma);
+}
+
+void vma_pgtable_walk_end(struct vm_area_struct *vma)
+{
+       if (is_vm_hugetlb_page(vma))
+               hugetlb_vma_unlock_read(vma);
+}