linux-kernel - Re: [PATCH 12/18] aio: make aio_setup

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Message-ID: <x491t7vmqxw.fsf@segfault.boston.devel.redhat.com>
Date:	Mon, 29 Feb 2016 11:17:31 -0500
From:	Jeff Moyer <jmoyer@...hat.com>
To:	Michal Hocko <mhocko@...nel.org>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	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>,
	Alexander Viro <viro@...iv.linux.org.uk>
Subject: Re: [PATCH 12/18] aio: make aio_setup_ring killable

Michal Hocko <mhocko@...nel.org> writes:

> From: Michal Hocko <mhocko@...e.com>
>
> aio_setup_ring waits for mmap_sem in writable mode. 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. This will also expedite
> the return to the userspace and do_exit.
>
> Cc: Benjamin LaHaise <bcrl@...ck.org>
> Cc: Alexander Viro <viro@...iv.linux.org.uk>
> Signed-off-by: Michal Hocko <mhocko@...e.com>
> ---
>  fs/aio.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/fs/aio.c b/fs/aio.c
> index 56bcdf4105f4..1c2e7e2c1b2b 100644
> --- a/fs/aio.c
> +++ b/fs/aio.c
> @@ -520,7 +520,12 @@ static int aio_setup_ring(struct kioctx *ctx)
>  	ctx->mmap_size = nr_pages * PAGE_SIZE;
>  	pr_debug("attempting mmap of %lu bytes\n", ctx->mmap_size);
>  
> -	down_write(&mm->mmap_sem);
> +	if (down_write_killable(&mm->mmap_sem)) {
> +		ctx->mmap_size = 0;
> +		aio_free_ring(ctx);
> +		return -EINTR;
> +	}
> +
>  	ctx->mmap_base = do_mmap_pgoff(ctx->aio_ring_file, 0, ctx->mmap_size,
>  				       PROT_READ | PROT_WRITE,
>  				       MAP_SHARED, 0, &unused);

Reviewed-by: Jeff Moyer <jmoyer@...hat.com>