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Date: Thu, 10 Mar 2016 16:56:55 +0100
From: Michal Hocko <mhocko@kernel.org>
Subject: Re: [PATCH 01/18] mm: Make mmap_sem for write waits killable for mm
 syscalls
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To: Vlastimil Babka <vbabka@suse.cz>
Cc: LKML <linux-kernel@vger.kernel.org>, Andrew Morton <akpm@linux-foundation.org>, linux-mm@kvack.org, Alex Deucher <alexander.deucher@amd.com>, Alex Thorlton <athorlton@sgi.com>, Andrea Arcangeli <aarcange@redhat.com>, Andy Lutomirski <luto@amacapital.net>, Benjamin LaHaise <bcrl@kvack.org>, Christian =?iso-8859-1?Q?K=F6nig?= <christian.koenig@amd.com>, Daniel Vetter <daniel.vetter@intel.com>, Dave Hansen <dave.hansen@linux.intel.com>, David Airlie <airlied@linux.ie>, Davidlohr Bueso <dave@stgolabs.net>, David Rientjes <rientjes@google.com>, "H . Peter Anvin" <hpa@zytor.com>, Hugh Dickins <hughd@google.com>, Ingo Molnar <mingo@kernel.org>, Johannes Weiner <hannes@cmpxchg.org>, "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>, Konstantin Khlebnikov <koct9i@gmail.com>, linux-arch@vger.kernel.org, Mel Gorman <mgorman@suse.de>, Oleg Nesterov <oleg@redhat.com>, Peter Zijlstra <peterz@infradead.org>, Petr Cermak <petrcermak@chromium.org>, Thomas Gleixner <tglx@linutronix.de>
Message-ID: <20160310155655.d6KLL8HIOxfc7Wyw1N1-lbSrgHhDnJ-F6hYt-HK6Jqg@z>

On Thu 10-03-16 16:47:16, Vlastimil Babka wrote:
> On 02/29/2016 02:26 PM, Michal Hocko wrote:
> >From: Michal Hocko <mhocko@suse.com>
> >
> >This is the first step in making mmap_sem write holders killable. It
> 
> s/holders/waiters/?

right. Fixed
 
> >focuses on the trivial ones which are taking the lock early after
> >entering the syscall and they are not changing state before.
> >
> >Therefore it is very easy to change them to use down_write_killable
> >and immediately return with -EINTR. This will allow the waiter to
> >pass away without blocking the mmap_sem which might be required to
> >make a forward progress. E.g. the oom reaper will need the lock for
> >reading to dismantle the OOM victim address space.
> >
> >The only tricky function in this patch is vm_mmap_pgoff which has many
> >call sites via vm_mmap. To reduce the risk keep vm_mmap with the
> >original non-killable semantic for now.
> >
> >vm_munmap callers do not bother checking the return value so open code
> >it into the munmap syscall path for now for simplicity.
> >
> >Cc: Mel Gorman <mgorman@suse.de>
> >Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
> >Cc: Konstantin Khlebnikov <koct9i@gmail.com>
> >Cc: Hugh Dickins <hughd@google.com>
> >Cc: Andrea Arcangeli <aarcange@redhat.com>
> >Cc: David Rientjes <rientjes@google.com>
> >Cc: Dave Hansen <dave.hansen@linux.intel.com>
> >Cc: Johannes Weiner <hannes@cmpxchg.org>
> >Signed-off-by: Michal Hocko <mhocko@suse.com>
> 
> Acked-by: Vlastimil Babka <vbabka@suse.cz>

Thanks!
-- 
Michal Hocko
SUSE Labs