diff options
| author | Yu Zhao <yuzhao@google.com> | 2024-07-11 22:19:56 +0300 |
|---|---|---|
| committer | Andrew Morton <akpm@linux-foundation.org> | 2024-07-18 07:05:18 +0300 |
| commit | 8b671fe1a879923ecfb72dda6caf01460dd885ef (patch) | |
| tree | 6f25ff50591df68a2d2df6864e06d9eeef9e6259 /mm | |
| parent | 0b84780134fb02525ef29ddcb88c3d560ba88a9c (diff) | |
| download | linux-8b671fe1a879923ecfb72dda6caf01460dd885ef.tar.xz | |
mm/mglru: fix div-by-zero in vmpressure_calc_level()
evict_folios() uses a second pass to reclaim folios that have gone through
page writeback and become clean before it finishes the first pass, since
folio_rotate_reclaimable() cannot handle those folios due to the
isolation.
The second pass tries to avoid potential double counting by deducting
scan_control->nr_scanned. However, this can result in underflow of
nr_scanned, under a condition where shrink_folio_list() does not increment
nr_scanned, i.e., when folio_trylock() fails.
The underflow can cause the divisor, i.e., scale=scanned+reclaimed in
vmpressure_calc_level(), to become zero, resulting in the following crash:
[exception RIP: vmpressure_work_fn+101]
process_one_work at ffffffffa3313f2b
Since scan_control->nr_scanned has no established semantics, the potential
double counting has minimal risks. Therefore, fix the problem by not
deducting scan_control->nr_scanned in evict_folios().
Link: https://lkml.kernel.org/r/20240711191957.939105-1-yuzhao@google.com
Fixes: 359a5e1416ca ("mm: multi-gen LRU: retry folios written back while isolated")
Reported-by: Wei Xu <weixugc@google.com>
Signed-off-by: Yu Zhao <yuzhao@google.com>
Cc: Alexander Motin <mav@ixsystems.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'mm')
| -rw-r--r-- | mm/vmscan.c | 1 |
1 files changed, 0 insertions, 1 deletions
diff --git a/mm/vmscan.c b/mm/vmscan.c index 0761f91b407f..6403038c776e 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -4597,7 +4597,6 @@ retry: /* retry folios that may have missed folio_rotate_reclaimable() */ list_move(&folio->lru, &clean); - sc->nr_scanned -= folio_nr_pages(folio); } spin_lock_irq(&lruvec->lru_lock); |