diff options
| author | Muchun Song <songmuchun@bytedance.com> | 2022-07-05 20:35:32 +0800 |
|---|---|---|
| committer | akpm <akpm@linux-foundation.org> | 2022-07-18 15:07:51 -0700 |
| commit | f4f451a16dd1f478fdb966bcbb612c1e4ce6b962 (patch) | |
| tree | ba7ad5ecab87d49ca86ff1034c6aa4526aad538b /mm | |
| parent | 3fe2895cfecd03ac74977f32102b966b6589f481 (diff) | |
mm: fix missing wake-up event for FSDAX pages
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()). This results in a task being permanently
stuck in TASK_INTERRUPTIBLE state.
Since FSDAX pages are only possibly obtained 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>
Diffstat (limited to 'mm')
| -rw-r--r-- | mm/gup.c | 6 | ||||
| -rw-r--r-- | mm/memremap.c | 6 |
2 files changed, 7 insertions, 5 deletions
@@ -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 *folio, int refs, unsigned int flags) refs *= GUP_PIN_COUNTING_BIAS; } - folio_put_refs(folio, refs); + if (!put_devmap_managed_page_refs(&folio->page, refs)) + folio_put_refs(folio, refs); } /** diff --git a/mm/memremap.c b/mm/memremap.c index b870a659eee6..745eea0f99c3 100644 --- a/mm/memremap.c +++ b/mm/memremap.c @@ -499,7 +499,7 @@ void free_zone_device_page(struct page *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 page *page) * 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 */ |