The patch titled Subject: mm: fix missing wake-up event for FSDAX pages has been added to the -mm mm-hotfixes-unstable branch. Its filename is mm-fix-missing-wake-up-event-for-fsdax-pages.patch
This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches...
This patch will later appear in the mm-hotfixes-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------ From: Muchun Song songmuchun@bytedance.com Subject: mm: fix missing wake-up event for FSDAX pages Date: Tue, 5 Jul 2022 20:35:32 +0800
FSDAX page refcounts are 1-based, rather than 0-based: if refcount is 1, then the page is freed. The FSDAX pages can be pinned through GUP, then they will be unpinned via unpin_user_page() using a folio variant to put the page, however, folio variants did not consider this special case, the result will be to miss a wakeup event (like the user of __fuse_dax_break_layouts()). Since FSDAX pages are only possible get by GUP users, so fix GUP instead of folio_put() to lower overhead.
Link: https://lkml.kernel.org/r/20220705123532.283-1-songmuchun@bytedance.com Fixes: d8ddc099c6b3 ("mm/gup: Add gup_put_folio()") Signed-off-by: Muchun Song songmuchun@bytedance.com Suggested-by: Matthew Wilcox willy@infradead.org Cc: Jason Gunthorpe jgg@ziepe.ca Cc: John Hubbard jhubbard@nvidia.com Cc: William Kucharski william.kucharski@oracle.com Cc: Dan Williams dan.j.williams@intel.com Cc: Jan Kara jack@suse.cz Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---
include/linux/mm.h | 14 +++++++++----- mm/gup.c | 6 ++++-- mm/memremap.c | 6 +++--- 3 files changed, 16 insertions(+), 10 deletions(-)
--- a/include/linux/mm.h~mm-fix-missing-wake-up-event-for-fsdax-pages +++ a/include/linux/mm.h @@ -1130,23 +1130,27 @@ static inline bool is_zone_movable_page( #if defined(CONFIG_ZONE_DEVICE) && defined(CONFIG_FS_DAX) DECLARE_STATIC_KEY_FALSE(devmap_managed_key);
-bool __put_devmap_managed_page(struct page *page); -static inline bool put_devmap_managed_page(struct page *page) +bool __put_devmap_managed_page_refs(struct page *page, int refs); +static inline bool put_devmap_managed_page_refs(struct page *page, int refs) { if (!static_branch_unlikely(&devmap_managed_key)) return false; if (!is_zone_device_page(page)) return false; - return __put_devmap_managed_page(page); + return __put_devmap_managed_page_refs(page, refs); } - #else /* CONFIG_ZONE_DEVICE && CONFIG_FS_DAX */ -static inline bool put_devmap_managed_page(struct page *page) +static inline bool put_devmap_managed_page_refs(struct page *page, int refs) { return false; } #endif /* CONFIG_ZONE_DEVICE && CONFIG_FS_DAX */
+static inline bool put_devmap_managed_page(struct page *page) +{ + return put_devmap_managed_page_refs(page, 1); +} + /* 127: arbitrary random number, small enough to assemble well */ #define folio_ref_zero_or_close_to_overflow(folio) \ ((unsigned int) folio_ref_count(folio) + 127u <= 127u) --- a/mm/gup.c~mm-fix-missing-wake-up-event-for-fsdax-pages +++ a/mm/gup.c @@ -87,7 +87,8 @@ retry: * belongs to this folio. */ if (unlikely(page_folio(page) != folio)) { - folio_put_refs(folio, refs); + if (!put_devmap_managed_page_refs(&folio->page, refs)) + folio_put_refs(folio, refs); goto retry; }
@@ -176,7 +177,8 @@ static void gup_put_folio(struct folio * refs *= GUP_PIN_COUNTING_BIAS; }
- folio_put_refs(folio, refs); + if (!put_devmap_managed_page_refs(&folio->page, refs)) + folio_put_refs(folio, refs); }
/** --- a/mm/memremap.c~mm-fix-missing-wake-up-event-for-fsdax-pages +++ a/mm/memremap.c @@ -499,7 +499,7 @@ void free_zone_device_page(struct page * }
#ifdef CONFIG_FS_DAX -bool __put_devmap_managed_page(struct page *page) +bool __put_devmap_managed_page_refs(struct page *page, int refs) { if (page->pgmap->type != MEMORY_DEVICE_FS_DAX) return false; @@ -509,9 +509,9 @@ bool __put_devmap_managed_page(struct pa * refcount is 1, then the page is free and the refcount is * stable because nobody holds a reference on the page. */ - if (page_ref_dec_return(page) == 1) + if (page_ref_sub_return(page, refs) == 1) wake_up_var(&page->_refcount); return true; } -EXPORT_SYMBOL(__put_devmap_managed_page); +EXPORT_SYMBOL(__put_devmap_managed_page_refs); #endif /* CONFIG_FS_DAX */ _
Patches currently in -mm which might be from songmuchun@bytedance.com are
mm-fix-missing-wake-up-event-for-fsdax-pages.patch mm-memcontrol-remove-dead-code-and-comments.patch mm-rename-unlock_page_lruvec_irq-_irqrestore-to-lruvec_unlock_irq-_irqrestore.patch mm-memcontrol-prepare-objcg-api-for-non-kmem-usage.patch mm-memcontrol-make-lruvec-lock-safe-when-lru-pages-are-reparented.patch mm-vmscan-rework-move_pages_to_lru.patch mm-thp-make-split-queue-lock-safe-when-lru-pages-are-reparented.patch mm-memcontrol-make-all-the-callers-of-foliopage_memcg-safe.patch mm-memcontrol-introduce-memcg_reparent_ops.patch mm-memcontrol-use-obj_cgroup-apis-to-charge-the-lru-pages.patch mm-lru-add-vm_warn_on_once_folio-to-lru-maintenance-function.patch mm-hugetlb_vmemmap-delete-hugetlb_optimize_vmemmap_enabled.patch mm-hugetlb_vmemmap-optimize-vmemmap_optimize_mode-handling.patch mm-hugetlb_vmemmap-introduce-the-name-hvo.patch mm-hugetlb_vmemmap-move-vmemmap-code-related-to-hugetlb-to-hugetlb_vmemmapc.patch mm-hugetlb_vmemmap-replace-early_param-with-core_param.patch mm-hugetlb_vmemmap-improve-hugetlb_vmemmap-code-readability.patch mm-hugetlb_vmemmap-move-code-comments-to-vmemmap_deduprst.patch mm-hugetlb_vmemmap-use-ptrs_per_pte-instead-of-pmd_size-page_size.patch