linux-kernel - [PATCH 16/18] drm/i915: make i915_gem_mmap_ioctl wait for mmap

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Date:	Tue, 26 Apr 2016 14:56:23 +0200
From:	Michal Hocko <mhocko@...nel.org>
To:	<linux-mm@...ck.org>, Andrew Morton <akpm@...ux-foundation.org>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Michal Hocko <mhocko@...e.com>,
	Daniel Vetter <daniel.vetter@...el.com>,
	David Airlie <airlied@...ux.ie>,
	Vlastimil Babka <vbabka@...e.cz>
Subject: [PATCH 16/18] drm/i915: make i915_gem_mmap_ioctl wait for mmap_sem killable

From: Michal Hocko <mhocko@...e.com>

i915_gem_mmap_ioctl relies on mmap_sem for write. If the waiting
task gets killed by the oom killer 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.

Cc: Daniel Vetter <daniel.vetter@...el.com>
Cc: David Airlie <airlied@...ux.ie>
Acked-by: Vlastimil Babka <vbabka@...e.cz>
Signed-off-by: Michal Hocko <mhocko@...e.com>
---
 drivers/gpu/drm/i915/i915_gem.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 761e28febddc..b99c761846ce 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -1721,7 +1721,10 @@ i915_gem_mmap_ioctl(struct drm_device *dev, void *data,
 		struct mm_struct *mm = current->mm;
 		struct vm_area_struct *vma;
 
-		down_write(&mm->mmap_sem);
+		if (down_write_killable(&mm->mmap_sem)) {
+			drm_gem_object_unreference_unlocked(obj);
+			return -EINTR;
+		}
 		vma = find_vma(mm, addr);
 		if (vma)
 			vma->vm_page_prot =
-- 
2.8.0.rc3