diff options
| author | Weilin Tong <tongweilin@linux.alibaba.com> | 2026-10-14 16:22:18 +0800 |
|---|---|---|
| committer | Andrew Morton <akpm@linux-foundation.org> | 2026-10-24 01:56:34 -0700 |
| commit | e387ebe5cd31720b1e0281fd045be4eef36fadb3 (patch) | |
| tree | 7be9d0afc55d2fece2761d7f02b56576e8b4d222 /ipc | |
| parent | 00a51d09912a12232d47bc282b74397908d1ed5c (diff) | |
ipc/shm: fix RSS accounting for hugetlb shared memory
Commit a08c7193e4f1 ("mm/filemap: remove hugetlb special casing in
filemap.c") changed mapping->nrpages to count base pages for hugetlb
folios. However, shm_add_rss_swap() still multiplies it by
pages_per_huge_page(), overcounting RSS in both SHM_INFO and
/proc/sysvipc/shm.
Use mapping->nrpages for RSS accounting across all backing types, and
account swap only for non-hugetlb shmem. Use READ_ONCE() for both
counters instead of info->lock, which does not protect nrpages and cannot
provide a consistent snapshot.
Link: https://lore.kernel.org/20261014082218.2236088-1-tongweilin@linux.alibaba.com
Fixes: a08c7193e4f1 ("mm/filemap: remove hugetlb special casing in filemap.c")
Signed-off-by: Weilin Tong <tongweilin@linux.alibaba.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Suggested-by: Muchun Song <muchun.song@linux.dev>
Acked-by: Muchun Song <muchun.song@linux.dev>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: David Hildenbrand <david@kernel.org>
Cc: Sidhartha Kumar <sidhartha.kumar@oracle.com>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Dan Carpenter <error27@gmail.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: <stable@vger.kernel.org>
Diffstat (limited to 'ipc')
| -rw-r--r-- | ipc/shm.c | 23 |
1 files changed, 4 insertions, 19 deletions
diff --git a/ipc/shm.c b/ipc/shm.c index bb1a721a3e74..6862f681373f 100644 --- a/ipc/shm.c +++ b/ipc/shm.c @@ -936,26 +936,11 @@ static inline unsigned long copy_shminfo_to_user(void __user *buf, struct shminf static void shm_add_rss_swap(struct shmid_kernel *shp, unsigned long *rss_add, unsigned long *swp_add) { - struct inode *inode; + struct inode *inode = file_inode(shp->shm_file); - inode = file_inode(shp->shm_file); - - if (is_file_hugepages(shp->shm_file)) { - struct address_space *mapping = inode->i_mapping; - struct hstate *h = hstate_file(shp->shm_file); - *rss_add += pages_per_huge_page(h) * mapping->nrpages; - } else { -#ifdef CONFIG_SHMEM - struct shmem_inode_info *info = SHMEM_I(inode); - - spin_lock_irq(&info->lock); - *rss_add += inode->i_mapping->nrpages; - *swp_add += info->swapped; - spin_unlock_irq(&info->lock); -#else - *rss_add += inode->i_mapping->nrpages; -#endif - } + *rss_add += READ_ONCE(inode->i_mapping->nrpages); + if (IS_ENABLED(CONFIG_SHMEM) && !is_file_hugepages(shp->shm_file)) + *swp_add += READ_ONCE(SHMEM_I(inode)->swapped); } /* |