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From: Kevin Wolf <kwolf@redhat.com>
To: Nicholas Thomas <nick@bytemark.co.uk>
Cc: qemu-trivial@nongnu.org, qemu-devel@nongnu.org
Subject: Re: [Qemu-trivial] [Qemu-devel] [PATCH] block/curl: Handle failed reads gracefully.
Date: Fri, 19 Aug 2011 01:00:33 +0200	[thread overview]
Message-ID: <4E4D9991.60707@redhat.com> (raw)
In-Reply-To: <1313398834.17401.135.camel@desk4.office.bytemark.co.uk>

Am 15.08.2011 11:00, schrieb Nicholas Thomas:
> Current behaviour if a read fails is for the acb to not get finished.
> This causes an infinite loop in bdrv_read_em (block.c). The read failure
> never gets reported to the  guest and if the error condition clears, the
> process never recovers.
> 
> With this patch, when curl reports a failure we finish the acb as a
> failure. This results in the guest receiving an I/O error (rather than
> the read hanging indefinitely) and if the error condition subsequently
> clears, retries work as expected.
> 
> The simplest test is to put an ISO on a web server you have control over
> and open it with qemu-io. Then move the ISO out of the way and attempt
> to read some data - you should see behaviour matching the above.
> 
> Signed-off-by: Nick Thomas <nick@bytemark.co.uk>

Thanks, applied to the block branch.

Kevin


WARNING: multiple messages have this Message-ID (diff)
From: Kevin Wolf <kwolf@redhat.com>
To: Nicholas Thomas <nick@bytemark.co.uk>
Cc: qemu-trivial@nongnu.org, qemu-devel@nongnu.org
Subject: Re: [Qemu-devel] [PATCH] block/curl: Handle failed reads gracefully.
Date: Fri, 19 Aug 2011 01:00:33 +0200	[thread overview]
Message-ID: <4E4D9991.60707@redhat.com> (raw)
In-Reply-To: <1313398834.17401.135.camel@desk4.office.bytemark.co.uk>

Am 15.08.2011 11:00, schrieb Nicholas Thomas:
> Current behaviour if a read fails is for the acb to not get finished.
> This causes an infinite loop in bdrv_read_em (block.c). The read failure
> never gets reported to the  guest and if the error condition clears, the
> process never recovers.
> 
> With this patch, when curl reports a failure we finish the acb as a
> failure. This results in the guest receiving an I/O error (rather than
> the read hanging indefinitely) and if the error condition subsequently
> clears, retries work as expected.
> 
> The simplest test is to put an ISO on a web server you have control over
> and open it with qemu-io. Then move the ISO out of the way and attempt
> to read some data - you should see behaviour matching the above.
> 
> Signed-off-by: Nick Thomas <nick@bytemark.co.uk>

Thanks, applied to the block branch.

Kevin

  reply	other threads:[~2011-08-18 22:57 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-08-15  9:00 [Qemu-trivial] [PATCH] block/curl: Handle failed reads gracefully Nicholas Thomas
2011-08-15  9:00 ` [Qemu-devel] " Nicholas Thomas
2011-08-18 23:00 ` Kevin Wolf [this message]
2011-08-18 23:00   ` Kevin Wolf

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