From: "Martin K. Petersen" <martin.petersen@oracle.com>
To: Ming Lei <ming.lei@canonical.com>
Cc: James Bottomley <JBottomley@parallels.com>,
Christoph Hellwig <hch@lst.de>,
linux-scsi@vger.kernel.org,
"Martin K. Petersen" <martin.petersen@oracle.com>,
Paolo Bonzini <pbonzini@redhat.com>
Subject: Re: [PATCH] SCSI: SD: set max_ws_blocks as max_unmap_blocks if it isn't provided
Date: Fri, 05 Dec 2014 07:56:15 -0500 [thread overview]
Message-ID: <yq1r3wefe6o.fsf@sermon.lab.mkp.net> (raw)
In-Reply-To: <1417782952-19908-1-git-send-email-ming.lei@canonical.com> (Ming Lei's message of "Fri, 5 Dec 2014 20:35:51 +0800")
>>>>> "Ming" == Ming Lei <ming.lei@canonical.com> writes:
Ming,
Ming> QEMU SCSI device claims to support UNMAP, WRITE SAME and WRITE
Ming> SAME 16 in LBP VPD page, but only provides "Maximum unmap LBA
Ming> count" in block limits VPD page, and "Maximum write same length"
Ming> isn't set.
That really sounds like a problem that should be fixed in QEMU SCSI.
Ming> The default max_discard_sectors(SD_MAX_WS16_BLOCKS) can't work at
Ming> all since it is much bigger than the actual Maximum unmap LBA
Ming> count.
There is absolutely no correlation between max write same blocks and max
unmap blocks. They are two entirely different commands. If QEMU SCSI
advertises support for WRITE SAME(16) and does not report a cap in the
block limits VPD then we must expect that it supports the maximum number
of blocks that can be expressed by the command.
--
Martin K. Petersen Oracle Linux Engineering
next prev parent reply other threads:[~2014-12-05 12:56 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-12-05 12:35 [PATCH] SCSI: SD: set max_ws_blocks as max_unmap_blocks if it isn't provided Ming Lei
2014-12-05 12:56 ` Martin K. Petersen [this message]
2014-12-05 13:05 ` Ming Lei
2014-12-05 13:22 ` Martin K. Petersen
2014-12-05 13:37 ` Ming Lei
2014-12-05 13:38 ` Martin K. Petersen
2014-12-05 13:47 ` Ming Lei
2014-12-05 13:58 ` Martin K. Petersen
2014-12-05 14:19 ` Ming Lei
2014-12-05 15:43 ` Paolo Bonzini
2014-12-30 12:51 ` Christoph Hellwig
2014-12-05 15:49 ` Paolo Bonzini
2014-12-05 16:21 ` Ming Lei
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