hugetlb: only adjust reservation during unmapping if mapcount is 0

Browse source

Since df7a6d1f64, __unmap_hugepage_range can adjust reservations.  In
the case of folio mapped in both a parent and a child, if the parent
unmaps the range first, the reservation adjustment will result in an
underflow of the reserved count.  Once the child unmaps the range, the
count is restored.  Change __unmap_hugepage_range() to check the mapcount
before adjusting the reservation.

Link: https://lore.kernel.org/all/alEJkwn5VlTTH_ZX@bender.morinfr.org/
Link: https://lore.kernel.org/amkC_1Ya6OiUoiLZ@bender.morinfr.org
Fixes: df7a6d1f64 ("mm/hugetlb: restore the reservation if needed")
Signed-off-by: Guillaume Morin <guillaume@morinfr.org>
Reviewed-by: Breno Leitao <leitao@debian.org>
Reviewed-by: Rik van Riel <riel@surriel.com>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: David Hildenbrand <david@kernel.org>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

...

This commit is contained in:

Guillaume Morin 2026-07-28 21:29:03 +02:00 • committed by Andrew Morton

parent 62e39381b7

commit 5120b1e048

1 changed files with 6 additions and 2 deletions

Show all changes Ignore whitespace when comparing lines Ignore changes in amount of whitespace Ignore changes in whitespace at EOL

Download patch file Download diff file Expand all files Collapse all files

8

mm/hugetlb.c

View file