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hugetlb: evaluate subpool free state while locked

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unlock_or_release_subpool() drops spool->lock before calling
subpool_is_free().  However, subpool_is_free() reads fields that are
updated under spool->lock, including count, used_hpages and rsv_hpages.

Keep the free-state evaluation under the same lock that protects those
fields.  The reservation accounting and kfree() calls still happen after
dropping spool->lock.

Link: https://lore.kernel.org/20260721035207.1437935-1-chenyichong@uniontech.com
Signed-off-by: Yichong Chen <chenyichong@uniontech.com>
Reviewed-by: Joshua Hahn <joshua.hahnjy@gmail.com>
Reviewed-by: Jane Chu <jane.chu@oracle.com>
Cc: David Hildenbrand <david@kernel.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Oscar Salvador <osalvador@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Yichong Chen
2026-07-21 11:52:07 +08:00
committed by Andrew Morton
parent 64a853c9a6
commit 47f3cecd72
1 changed files with 4 additions and 2 deletions
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6
mm/hugetlb.c
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@@ -141,12 +141,14 @@ static inline bool subpool_is_free(struct hugepage_subpool *spool)
static inline void unlock_or_release_subpool(struct hugepage_subpool *spool,
unsigned long irq_flags)
{
spin_unlock_irqrestore(&spool->lock, irq_flags);
bool free_subpool = subpool_is_free(spool);
/* If no pages are used, and no other handles to the subpool
* remain, give up any reservations based on minimum size and
* free the subpool */
if (subpool_is_free(spool)) {
spin_unlock_irqrestore(&spool->lock, irq_flags);
if (free_subpool) {
if (spool->min_hpages != -1)
hugetlb_acct_memory(spool->hstate,
-spool->min_hpages);