From: Paolo Bonzini <pbonzini@redhat.com>
To: Christoph Hellwig <hch@lst.de>
Cc: Kevin Wolf <kwolf@redhat.com>, qemu-devel@nongnu.org
Subject: [Qemu-devel] Re: [PATCH 1/5] block: add discard support
Date: Mon, 13 Dec 2010 17:07:27 +0100 [thread overview]
Message-ID: <4D0644BF.3020701@redhat.com> (raw)
In-Reply-To: <20101210133843.GA28846@lst.de>
On 12/10/2010 02:38 PM, Christoph Hellwig wrote:
> if it's smaller than the block size we'll zero out the remainder of
> the block.
I think it should fail at VM startup time, or even better do nothing at all.
When you write in the middle of an absent block, and a partially-zero
block is created, this is not visible: a read cannot see the difference
between "all zeros because it's sparse" and "all zeros because it's zero".
If I ask you to (optionally) punch a 1kb hole but all you can do is
punch a 2kb hole, I do care about the second kilobyte of data. Since
the hole punching of bdrv_discard is completely optional, it should not
be done in this case.
Paolo
next prev parent reply other threads:[~2010-12-13 16:07 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-11-25 13:56 [Qemu-devel] [PATCH 0/5] add TRIM/UNMAP support Christoph Hellwig
2010-11-25 13:57 ` [Qemu-devel] [PATCH 1/5] block: add discard support Christoph Hellwig
2010-11-25 14:09 ` malc
2010-11-25 14:45 ` Stefan Hajnoczi
2010-11-25 13:57 ` [Qemu-devel] [PATCH 2/5] scsi-disk: support WRITE SAME (16) with unmap bit Christoph Hellwig
2010-11-25 14:10 ` malc
2010-11-25 13:57 ` [Qemu-devel] [PATCH 3/5] make dma_bdrv_io available to drivers Christoph Hellwig
2010-11-25 13:57 ` [Qemu-devel] [PATCH 4/5] ide: add TRIM support Christoph Hellwig
2010-11-25 14:10 ` malc
2010-11-25 13:57 ` [Qemu-devel] [PATCH 5/5] raw-posix: add discard support Christoph Hellwig
2010-12-01 15:35 ` [Qemu-devel] PATCH 0/5] add TRIM/UNMAP support, v2 Christoph Hellwig
2010-12-01 15:35 ` [Qemu-devel] [PATCH 1/5] block: add discard support Christoph Hellwig
2010-12-02 12:12 ` Kevin Wolf
2010-12-10 13:38 ` Christoph Hellwig
2010-12-11 12:50 ` Paul Brook
2010-12-13 15:43 ` Christoph Hellwig
2010-12-13 16:17 ` Paul Brook
2010-12-13 16:07 ` Paolo Bonzini [this message]
2010-12-13 16:15 ` [Qemu-devel] " Christoph Hellwig
2010-12-13 16:24 ` Paolo Bonzini
2010-12-01 15:35 ` [Qemu-devel] [PATCH 2/5] scsi-disk: support WRITE SAME (16) with unmap bit Christoph Hellwig
2010-12-01 15:35 ` [Qemu-devel] [PATCH 3/5] make dma_bdrv_io available to drivers Christoph Hellwig
2010-12-01 15:35 ` [Qemu-devel] [PATCH 4/5] ide: add TRIM support Christoph Hellwig
2010-12-02 14:07 ` Kevin Wolf
2010-12-10 13:39 ` Christoph Hellwig
2010-12-01 15:35 ` [Qemu-devel] [PATCH 5/5] raw-posix: add discard support Christoph Hellwig
2010-12-02 12:04 ` Kevin Wolf
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