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mm/filemap: do not count FAULT_FLAG_TRIED retries as mmap hits

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A fault that starts synchronous mmap readahead can return VM_FAULT_RETRY
after dropping mmap_lock.  The retry may then map the folio brought in by
that same miss.

Do not let this retry decrement mmap_miss.  The retry still maps the folio
from the page cache; it just does not count as a useful mmap readahead
hit.

Link: https://lore.kernel.org/tencent_22E6B8849EC1141FE7773C64467E6F1E2C09@qq.com
Signed-off-by: fujunjie <fujunjie1@qq.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Vishal Moola <vishal.moola@gmail.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
fujunjie 2026-04-28 01:59:44 +00:00 committed by Andrew Morton
parent 0b9c0aeba9
commit 9b0fcac3cf
1 changed files with 1 additions and 0 deletions
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mm/filemap.c
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@ -3937,6 +3937,7 @@ vm_fault_t filemap_map_pages(struct vm_fault *vmf,
* we can stop read-ahead.
*/
if ((map_ret & VM_FAULT_NOPAGE) &&
!(vmf->flags & FAULT_FLAG_TRIED) &&
!folio_test_workingset(folio)) {
unsigned short mmap_miss;