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mm, memcg: fix corruption on 64-bit divisor in memory.high throttling

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Commit 0e4b01df86 had a bunch of fixups to use the right division
method.  However, it seems that after all that it still wasn't right --
div_u64 takes a 32-bit divisor.

The headroom is still large (2^32 pages), so on mundane systems you
won't hit this, but this should definitely be fixed.

Fixes: 0e4b01df86 ("mm, memcg: throttle allocators when failing reclaim over memory.high")
Reported-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Chris Down <chris@chrisdown.name>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Roman Gushchin <guro@fb.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Nathan Chancellor <natechancellor@gmail.com>
Cc: <stable@vger.kernel.org>	[5.4.x+]
Link: http://lkml.kernel.org/r/80780887060514967d414b3cd91f9a316a16ab98.1584036142.git.chris@chrisdown.name
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Chris Down 2020-03-21 18:22:20 -07:00 committed by Linus Torvalds
parent d72520ad00
commit d397a45fc7
1 changed files with 1 additions and 1 deletions
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2
mm/memcontrol.c
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@ -2339,7 +2339,7 @@ void mem_cgroup_handle_over_high(void)
*/
clamped_high = max(high, 1UL);
overage = div_u64((u64)(usage - high) << MEMCG_DELAY_PRECISION_SHIFT,
overage = div64_u64((u64)(usage - high) << MEMCG_DELAY_PRECISION_SHIFT,
clamped_high);
penalty_jiffies = ((u64)overage * overage * HZ)