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mm: page-writeback: simplify memcg handling in test_clear_page_writeback()

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Page writeback doesn't hold a page reference, which allows truncate to
free a page the second PageWriteback is cleared.  This used to require
special attention in test_clear_page_writeback(), where we had to be
careful not to rely on the unstable page->memcg binding and look up all
the necessary information before clearing the writeback flag.

Since commit 073861ed77 ("mm: fix VM_BUG_ON(PageTail) and
BUG_ON(PageWriteback)") test_clear_page_writeback() is called with an
explicit reference on the page, and this dance is no longer needed.

Use unlock_page_memcg() and dec_lruvec_page_state() directly.

This removes the last user of the lock_page_memcg() return value, change
it to void.  Touch up the comments in there as well.  This also removes
the last extern user of __unlock_page_memcg(), make it static.  Further,
it removes the last user of dec_lruvec_state(), delete it, along with a
few other unused helpers.

Link: https://lkml.kernel.org/r/YCQbYAWg4nvBFL6h@cmpxchg.org
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Hugh Dickins <hughd@google.com>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Roman Gushchin <guro@fb.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Johannes Weiner 2021-04-29 22:55:32 -07:00 • committed by Linus Torvalds
parent 79e3094c53
commit 1c824a680b
4 changed files with 19 additions and 60 deletions
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10
include/linux/memcontrol.h
View file

@ -867,8 +867,7 @@ void mem_cgroup_print_oom_group(struct mem_cgroup *memcg);
extern bool cgroup_memory_noswap;
#endif
struct mem_cgroup *lock_page_memcg(struct page *page);
void __unlock_page_memcg(struct mem_cgroup *memcg);
void lock_page_memcg(struct page *page);
void unlock_page_memcg(struct page *page);
/*
@ -1289,12 +1288,7 @@ mem_cgroup_print_oom_meminfo(struct mem_cgroup *memcg)
{
}
static inline struct mem_cgroup *lock_page_memcg(struct page *page)
{
return NULL;
}
static inline void __unlock_page_memcg(struct mem_cgroup *memcg)
static inline void lock_page_memcg(struct page *page)
{
}