From: David Hildenbrand <david@redhat.com> mainline inclusion from mainline-v6.12-rc1 commit 3523a37e657c7cc97723a54e9dfacca6c003e4c1 category: bugfix bugzilla: https://gitee.com/src-openeuler/kernel/issues/IC2YHO CVE: NA Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... ------------------------------------------- Patch series "mm: replace follow_page() by folio_walk". Looking into a way of moving the last folio_likely_mapped_shared() call in add_folio_for_migration() under the PTL, I found myself removing follow_page(). This paves the way for cleaning up all the FOLL_, follow_* terminology to just be called "GUP" nowadays. The new page table walker will lookup a mapped folio and return to the caller with the PTL held, such that the folio cannot get unmapped concurrently. Callers can then conditionally decide whether they really want to take a short-term folio reference or whether the can simply unlock the PTL and be done with it. folio_walk is similar to page_vma_mapped_walk(), except that we don't know the folio we want to walk to and that we are only walking to exactly one PTE/PMD/PUD. folio_walk provides access to the pte/pmd/pud (and the referenced folio page because things like KSM need that), however, as part of this series no page table modifications are performed by users. We might be able to convert some other walk_page_range() users that really only walk to one address, such as DAMON with damon_mkold_ops/damon_young_ops. It might make sense to extend folio_walk in the future to optionally fault in a folio (if applicable), such that we can replace some get_user_pages() users that really only want to lookup a single page/folio under PTL without unconditionally grabbing a folio reference. I have plans to extend the approach to a range walker that will try batching various page table entries (not just folio pages) to be a better replace for walk_page_range() -- and users will be able to opt in which type of page table entries they want to process -- but that will require more work and more thoughts. KSM seems to work just fine (ksm_functional_tests selftests) and move_pages seems to work (migration selftest). I tested the leaf implementation excessively using various hugetlb sizes (64K, 2M, 32M, 1G) on arm64 using move_pages and did some more testing on x86-64. Cross compiled on a bunch of architectures. This patch (of 11): We want to make use of vm_normal_page_pmd() in generic page table walking code where we might walk hugetlb folios that are mapped by PMDs even without CONFIG_TRANSPARENT_HUGEPAGE. So let's expose vm_normal_page_pmd() + vm_normal_folio_pmd() with CONFIG_PGTABLE_HAS_HUGE_LEAVES. Link: https://lkml.kernel.org/r/20240802155524.517137-1-david@redhat.com Link: https://lkml.kernel.org/r/20240802155524.517137-2-david@redhat.com Signed-off-by: David Hildenbrand <david@redhat.com> Cc: Alexander Gordeev <agordeev@linux.ibm.com> Cc: Christian Borntraeger <borntraeger@linux.ibm.com> Cc: Claudio Imbrenda <imbrenda@linux.ibm.com> Cc: Gerald Schaefer <gerald.schaefer@linux.ibm.com> Cc: Heiko Carstens <hca@linux.ibm.com> Cc: Janosch Frank <frankja@linux.ibm.com> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Matthew Wilcox <willy@infradead.org> Cc: Sven Schnelle <svens@linux.ibm.com> Cc: Vasily Gorbik <gor@linux.ibm.com> Cc: Ryan Roberts <ryan.roberts@arm.com> Cc: Zi Yan <ziy@nvidia.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Jinjiang Tu <tujinjiang@huawei.com> --- mm/memory.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/mm/memory.c b/mm/memory.c index c76a1dae75d9..bfd431c72efb 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -665,7 +665,7 @@ struct folio *vm_normal_folio(struct vm_area_struct *vma, unsigned long addr, return NULL; } -#ifdef CONFIG_TRANSPARENT_HUGEPAGE +#ifdef CONFIG_PGTABLE_HAS_HUGE_LEAVES struct page *vm_normal_page_pmd(struct vm_area_struct *vma, unsigned long addr, pmd_t pmd) { -- 2.43.0