From: Sitsofe Wheeler <sitsofe@gmail.com>
To: "Darrick J. Wong" <darrick.wong@oracle.com>
Cc: Shaohua Li <shli@kernel.org>, Jens Axboe <axboe@kernel.dk>,
Arvind Kumar <arvindkumar@vmware.com>,
VMware PV-Drivers <pv-drivers@vmware.com>,
linux-raid@vger.kernel.org,
"linux-scsi@vger.kernel.org" <linux-scsi@vger.kernel.org>,
linux-block@vger.kernel.org,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: BLKZEROOUT not zeroing md dev on VMDK
Date: Fri, 27 May 2016 05:45:46 +0100 [thread overview]
Message-ID: <CALjAwxgkgPZdXFkOuD-7Dsbxf9oVEGuXTDLnyqu8rTrJio_4mA@mail.gmail.com> (raw)
In-Reply-To: <20160527041824.GC9418@birch.djwong.org>
On 27 May 2016 at 05:18, Darrick J. Wong <darrick.wong@oracle.com> wrote:
>
> It's possible that the pvscsi device advertised WRITE SAME, but if the device
> sends back ILLEGAL REQUEST then the SCSI disk driver will set
> write_same_max_bytes=0. Subsequent BLKZEROOUT attempts will then issue writes
> of zeroes to the drive.
Thanks for following up on this but that's not what happens on the md
device - you can go on to issue as many BLKZEROOUT requests as you
like but the md disk is never zeroed nor is an error returned.
I filed a bug at https://bugzilla.kernel.org/show_bug.cgi?id=118581
(see https://bugzilla.kernel.org/show_bug.cgi?id=118581#c6 for
alternative reproduction steps that use scsi_debug and can be reworked
to impact device mapper) and Shaohua Li noted that
blkdev_issue_write_same could return 0 even when the disk didn't
support write same (see
https://bugzilla.kernel.org/show_bug.cgi?id=118581#c8 ).
Shaohua went on to create a patch for this ("block: correctly fallback
for zeroout" - https://patchwork.kernel.org/patch/9137311/ ) which has
yet to be reviewed.
--
Sitsofe | http://sucs.org/~sits/
next prev parent reply other threads:[~2016-05-27 4:45 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-05-18 22:39 BLKZEROOUT not zeroing md dev on VMDK Sitsofe Wheeler
2016-05-27 4:18 ` Darrick J. Wong
2016-05-27 4:45 ` Sitsofe Wheeler [this message]
2016-05-27 9:30 ` Tom Yan
2016-06-01 5:04 ` Sitsofe Wheeler
2016-06-15 18:17 ` Arvind Kumar
2016-06-15 21:33 ` Sitsofe Wheeler
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