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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 /mm/memcontrol.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 'mm/memcontrol.c')
-rw-r--r--mm/memcontrol.c23
1 files changed, 0 insertions, 23 deletions
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 8c035846c7a4..7fdc001ce15f 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1047,29 +1047,6 @@ struct mem_cgroup *get_mem_cgroup_from_mm(struct mm_struct *mm)
}
EXPORT_SYMBOL(get_mem_cgroup_from_mm);
-/**
- * get_mem_cgroup_from_page: Obtain a reference on given page's memcg.
- * @page: page from which memcg should be extracted.
- *
- * Obtain a reference on page->memcg and returns it if successful. Otherwise
- * root_mem_cgroup is returned.
- */
-struct mem_cgroup *get_mem_cgroup_from_page(struct page *page)
-{
- struct mem_cgroup *memcg = page_memcg(page);
-
- if (mem_cgroup_disabled())
- return NULL;
-
- rcu_read_lock();
- /* Page should not get uncharged and freed memcg under us. */
- if (!memcg || WARN_ON_ONCE(!css_tryget(&memcg->css)))
- memcg = root_mem_cgroup;
- rcu_read_unlock();
- return memcg;
-}
-EXPORT_SYMBOL(get_mem_cgroup_from_page);
-
static __always_inline struct mem_cgroup *active_memcg(void)
{
if (in_interrupt())