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

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Message-ID: <56E2E2DC.9010806@suse.cz>
Date:	Fri, 11 Mar 2016 16:23:08 +0100
From:	Vlastimil Babka <vbabka@...e.cz>
To:	Michal Hocko <mhocko@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
	Alex Deucher <alexander.deucher@....com>,
	Alex Thorlton <athorlton@....com>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Andy Lutomirski <luto@...capital.net>,
	Benjamin LaHaise <bcrl@...ck.org>,
	Christian König <christian.koenig@....com>,
	Daniel Vetter <daniel.vetter@...el.com>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	David Airlie <airlied@...ux.ie>,
	Davidlohr Bueso <dave@...olabs.net>,
	David Rientjes <rientjes@...gle.com>,
	"H . Peter Anvin" <hpa@...or.com>, Hugh Dickins <hughd@...gle.com>,
	Ingo Molnar <mingo@...nel.org>,
	Johannes Weiner <hannes@...xchg.org>,
	"Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
	Konstantin Khlebnikov <koct9i@...il.com>,
	linux-arch@...r.kernel.org, Mel Gorman <mgorman@...e.de>,
	Oleg Nesterov <oleg@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Petr Cermak <petrcermak@...omium.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Michal Hocko <mhocko@...e.com>
Subject: Re: [PATCH 16/18] drm/i915: make i915_gem_mmap_ioctl wait for
 mmap_sem killable

On 02/29/2016 02:26 PM, Michal Hocko wrote:
> 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>
> Signed-off-by: Michal Hocko <mhocko@...e.com>

Acked-by: Vlastimil Babka <vbabka@...e.cz>

> ---
>   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 f68f34606f2f..a50136cbd332 100644
> --- a/drivers/gpu/drm/i915/i915_gem.c
> +++ b/drivers/gpu/drm/i915/i915_gem.c
> @@ -1754,7 +1754,10 @@ 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 =
>