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authorJohannes Weiner <hannes@cmpxchg.org>2021-02-24 23:04:15 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2021-02-25 00:38:30 +0300
commit6eeb104e114cb6b7391c2d69ff873403858c1f35 (patch)
tree5ed91e4614aaff0ed676995ad2f2db9761ae361a /fs/buffer.c
parenta7b7e1df892457935ec4f35ef9e9aa344758dbc9 (diff)
downloadlinux-6eeb104e114cb6b7391c2d69ff873403858c1f35.tar.xz
fs: buffer: use raw page_memcg() on locked page
alloc_page_buffers() currently uses get_mem_cgroup_from_page() for charging the buffers to the page owner, which does an rcu-protected page->memcg lookup and acquires a reference. But buffer allocation has the page lock held throughout, which pins the page to the memcg and thereby the memcg - neither rcu nor holding an extra reference during the allocation are necessary. Use a raw page_memcg() instead. This was the last user of get_mem_cgroup_from_page(), delete it. Link: https://lkml.kernel.org/r/20210209190126.97842-1-hannes@cmpxchg.org Signed-off-by: Johannes Weiner <hannes@cmpxchg.org> Reported-by: Muchun Song <songmuchun@bytedance.com> Reviewed-by: Shakeel Butt <shakeelb@google.com> Acked-by: Roman Gushchin <guro@fb.com> Acked-by: Michal Hocko <mhocko@suse.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'fs/buffer.c')
-rw-r--r--fs/buffer.c4
1 files changed, 2 insertions, 2 deletions
diff --git a/fs/buffer.c b/fs/buffer.c
index f1c3a5b27a90..0cb7ffd4977c 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -847,7 +847,8 @@ struct buffer_head *alloc_page_buffers(struct page *page, unsigned long size,
if (retry)
gfp |= __GFP_NOFAIL;
- memcg = get_mem_cgroup_from_page(page);
+ /* The page lock pins the memcg */
+ memcg = page_memcg(page);
old_memcg = set_active_memcg(memcg);
head = NULL;
@@ -868,7 +869,6 @@ struct buffer_head *alloc_page_buffers(struct page *page, unsigned long size,
}
out:
set_active_memcg(old_memcg);
- mem_cgroup_put(memcg);
return head;
/*
* In case anything failed, we just free everything we got.