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| author | Wenjie Qi <qiwenjie@xiaomi.com> | 2026-08-30 01:36:12 +0800 |
|---|---|---|
| committer | Andrew Morton <akpm@linux-foundation.org> | 2026-09-05 11:47:48 -0700 |
| commit | 848d2ce2fce15fbdc083fbf9691bfa72911033c4 (patch) | |
| tree | 3e5e1bd0b0d8cfab5d65ecd1955fbba94e9ae149 | |
| parent | e1d469a8d6c63032a5aed3679a13a086b61bd5cc (diff) | |
| download | linux-next-848d2ce2fce15fbdc083fbf9691bfa72911033c4.tar.gz linux-next-848d2ce2fce15fbdc083fbf9691bfa72911033c4.zip | |
mm: filemap: retain mapped dropbehind folios
Fault-around can map ready dropbehind folios without going through the
normal page-cache lookup that clears dropbehind. A mapping represents a
competing cached user, so retain the folio instead of forcibly unmapping
it when writeback completes.
For a mapped folio, folio_unmap_invalidate() can call
unmap_mapping_folio(), which takes i_mmap_rwsem and may sleep. Retaining
mapped folios avoids this path when folio_end_dropbehind() runs in
non-preemptible task context.
Tal was able to trigger a sleeping-in-atomic warning due to this [1].
Unmapped dropbehind folios continue through the existing invalidation path.
Link: https://lore.kernel.org/4aba05e1a2c3b61cb337d373eb9b7a8db4ddd822.1788024049.git.qiwenjie@xiaomi.com
Link: https://lore.kernel.org/076bb01b-6fcf-4691-be8c-0e8507c9fe64@columbia.edu [1]
Fixes: fb7d3bc41493 ("mm/filemap: drop streaming/uncached pages when writeback completes")
Signed-off-by: Wenjie Qi <qiwenjie@xiaomi.com>
Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Tal Zussman <tz2294@columbia.edu>
Tested-by: Tal Zussman <tz2294@columbia.edu>
Cc: Barry Song <baohua@kernel.org>
Cc: Jan Kara <jack@suse.cz>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Trond Myklebust <trond.myklebust@hammerspace.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
| -rw-r--r-- | mm/filemap.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/mm/filemap.c b/mm/filemap.c index 6afec636881f..00fd89cf6f55 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -1616,7 +1616,7 @@ static void filemap_end_dropbehind(struct folio *folio) return; if (!folio_test_clear_dropbehind(folio)) return; - if (mapping) + if (mapping && !folio_mapped(folio)) folio_unmap_invalidate(mapping, folio, 0); } |