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Date: Sat, 13 Aug 2016 19:07:45 +0200
From: Oleg Nesterov <oleg@redhat.com>
To: Bart Van Assche <bart.vanassche@sandisk.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
        "mingo@kernel.org" <mingo@kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
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        Michael Shaver <jmshaver@gmail.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] sched: Avoid that __wait_on_bit_lock() hangs
Message-ID: <20160813170744.GA2868@redhat.com>
References: <4091e252-18d9-1795-de63-9fbc678aa6b1@acm.org> <20160808162038.GA25927@redhat.com> <78fafdc1-d4ae-a9a2-169c-1d456b6e6e41@sandisk.com> <20160809171459.GA13840@redhat.com> <3cec7657-caa9-92ca-9f0e-34f073a6ed8c@sandisk.com> <20160810104555.GA3333@redhat.com> <4d2e02f8-c7da-ee1a-1068-25492cbffebe@sandisk.com> <20160811173651.GA31803@redhat.com> <20160812161611.GC30930@redhat.com> <ccb421f9-9d0a-6bb6-cd52-8ada311bbe9b@sandisk.com>
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Forgot to mention...

On 08/12, Bart Van Assche wrote:
>
> --- a/mm/filemap.c
> +++ b/mm/filemap.c
> @@ -1643,7 +1643,12 @@ find_page:
>  			 * wait_on_page_locked is used to avoid unnecessarily
>  			 * serialisations and why it's safe.
>  			 */
> -			wait_on_page_locked_killable(page);
> +			error = wait_on_page_locked_killable(page);
> +			if (error == -EINTR) {
> +				put_page(page);
> +				goto out;
> +			}
> +			error = 0;

This change probably makes sense regardless although I'd suggest to
simplify it:

	-		wait_on_page_locked_killable(page);
	+		error = wait_on_page_locked_killable(page);
	+		if (unlikely(error))
	+			goto readpage_error;


but it looks off-topic. And the changelog looks misleading/wrong.

I do not think this change makes sense in this debugging session,

Oleg.