From 4e80153a6044bcd9a7d65c1ec4b1d1c44ba0ed6c Mon Sep 17 00:00:00 2001
From: Michal Hocko <mhocko@suse.com>
Date: Mon, 23 May 2016 16:25:45 -0700
Subject: [PATCH] mm, proc: make clear_refs killable
CLEAR_REFS_MM_HIWATER_RSS and CLEAR_REFS_SOFT_DIRTY are relying on
mmap_sem for write. If the waiting task gets killed by the oom killer
and it would operate on the current's mm it would block oom_reaper from
asynchronous address space reclaim and reduce the chances of timely OOM
resolving. Wait for the lock in the killable mode and return with EINTR
if the task got killed while waiting. This will also expedite the
return to the userspace and do_exit even if the mm is remote.
Signed-off-by: Michal Hocko <mhocko@suse.com>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Petr Cermak <petrcermak@chromium.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
fs/proc/task_mmu.c | 11 +++++++++--
1 file changed, 9 insertions(+), 2 deletions(-)
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 541583510cfb..4648c7f63ae2 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -1027,11 +1027,15 @@ static ssize_t clear_refs_write(struct file *file, const char __user *buf,
};
if (type == CLEAR_REFS_MM_HIWATER_RSS) {
+ if (down_write_killable(&mm->mmap_sem)) {
+ count = -EINTR;
+ goto out_mm;
+ }
+
/*
* Writing 5 to /proc/pid/clear_refs resets the peak
* resident set size to this mm's current rss value.
*/
- down_write(&mm->mmap_sem);
reset_mm_hiwater_rss(mm);
up_write(&mm->mmap_sem);
goto out_mm;
@@ -1043,7 +1047,10 @@ static ssize_t clear_refs_write(struct file *file, const char __user *buf,
if (!(vma->vm_flags & VM_SOFTDIRTY))
continue;
up_read(&mm->mmap_sem);
- down_write(&mm->mmap_sem);
+ if (down_write_killable(&mm->mmap_sem)) {
+ count = -EINTR;
+ goto out_mm;
+ }
for (vma = mm->mmap; vma; vma = vma->vm_next) {
vma->vm_flags &= ~VM_SOFTDIRTY;
vma_set_page_prot(vma);