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| author | Johannes Weiner <hannes@cmpxchg.org> | 2021-02-24 12:04:15 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2021-02-24 13:38:30 -0800 |
| commit | 6eeb104e114cb6b7391c2d69ff873403858c1f35 (patch) | |
| tree | 5ed91e4614aaff0ed676995ad2f2db9761ae361a /fs/buffer.c | |
| parent | a7b7e1df892457935ec4f35ef9e9aa344758dbc9 (diff) | |
| download | lwn-6eeb104e114cb6b7391c2d69ff873403858c1f35.tar.gz lwn-6eeb104e114cb6b7391c2d69ff873403858c1f35.zip | |
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.c | 4 |
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. |