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[PATCH 07/18] mm, proc: make clear_refs killable

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From: Michal Hocko <mhocko@suse.com>

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.

Cc: Petr Cermak <petrcermak@chromium.org>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Michal Hocko <mhocko@suse.com>
---
 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);
-- 
2.8.0.rc3

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[PATCH 0/18] change mmap_sem taken for write killable v2 Michal Hocko <mhocko@kernel.org> - 2016-04-26 15:00 +0200
  [PATCH 09/18] ipc, shm: make shmem attach/detach wait for mmap_sem killable Michal Hocko <mhocko@kernel.org> - 2016-04-26 15:00 +0200
  [PATCH 07/18] mm, proc: make clear_refs killable Michal Hocko <mhocko@kernel.org> - 2016-04-26 15:00 +0200
  [PATCH 13/18] exec: make exec path waiting for mmap_sem killable Michal Hocko <mhocko@kernel.org> - 2016-04-26 15:00 +0200
  [PATCH 06/18] mm: make vm_brk killable Michal Hocko <mhocko@kernel.org> - 2016-04-26 15:00 +0200
  [PATCH 18/18] drm/amdgpu: make amdgpu_mn_get wait for mmap_sem killable Michal Hocko <mhocko@kernel.org> - 2016-04-26 15:00 +0200
  [PATCH 03/18] mm: make vm_munmap killable Michal Hocko <mhocko@kernel.org> - 2016-04-26 15:00 +0200
  [PATCH 08/18] mm, fork: make dup_mmap wait for mmap_sem for write killable Michal Hocko <mhocko@kernel.org> - 2016-04-26 15:00 +0200
  [PATCH 14/18] prctl: make PR_SET_THP_DISABLE wait for mmap_sem killable Michal Hocko <mhocko@kernel.org> - 2016-04-26 15:00 +0200
    Re: [PATCH 14/18] prctl: make PR_SET_THP_DISABLE wait for mmap_sem  killable Alex Thorlton <athorlton@sgi.com> - 2016-04-26 17:20 +0200
  [PATCH 16/18] drm/i915: make i915_gem_mmap_ioctl wait for mmap_sem killable Michal Hocko <mhocko@kernel.org> - 2016-04-26 15:00 +0200
  [PATCH 10/18] vdso: make arch_setup_additional_pages wait for mmap_sem for write killable Michal Hocko <mhocko@kernel.org> - 2016-04-26 15:00 +0200
  [PATCH 02/18] mm: make vm_mmap killable Michal Hocko <mhocko@kernel.org> - 2016-04-26 15:00 +0200
  [PATCH 11/18] coredump: make coredump_wait wait for mmap_sem for write killable Michal Hocko <mhocko@kernel.org> - 2016-04-26 15:00 +0200
  [PATCH 12/18] aio: make aio_setup_ring killable Michal Hocko <mhocko@kernel.org> - 2016-04-26 15:00 +0200
  [PATCH 04/18] mm, aout: handle vm_brk failures Michal Hocko <mhocko@kernel.org> - 2016-04-26 15:10 +0200
  [PATCH 05/18] mm, elf: handle vm_brk error Michal Hocko <mhocko@kernel.org> - 2016-04-26 15:10 +0200
  [PATCH 01/18] mm: Make mmap_sem for write waits killable for mm syscalls Michal Hocko <mhocko@kernel.org> - 2016-04-26 15:10 +0200

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