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Re: [Qemu-devel] [Qemu-trivial] [PATCH] Teach block/vdi about "discarded
From: |
Stefan Hajnoczi |
Subject: |
Re: [Qemu-devel] [Qemu-trivial] [PATCH] Teach block/vdi about "discarded" (no longer allocated) blocks |
Date: |
Thu, 27 Oct 2011 08:05:36 +0100 |
User-agent: |
Mutt/1.5.21 (2010-09-15) |
On Wed, Oct 26, 2011 at 03:51:18PM -0400, Eric Sunshine wrote:
> An entry in the VDI block map will hold an offset to the actual block if
> the block is allocated, or one of two specially-interpreted values if
> not allocated. Using VirtualBox terminology, value VDI_IMAGE_BLOCK_FREE
> (0xffffffff) represents a never-allocated block (semantically arbitrary
> content). VDI_IMAGE_BLOCK_ZERO (0xfffffffe) represents a "discarded"
> block (semantically zero-filled). block/vdi knows only about
> VDI_IMAGE_BLOCK_FREE. Teach it about VDI_IMAGE_BLOCK_ZERO.
>
> Signed-off-by: Eric Sunshine <address@hidden>
> ---
>
> Without this patch, "qemu-image check" on a VDI image containing
> discarded blocks reports errors such as:
>
> ERROR: block index 3434 too large, is 4294967294
>
> Decimal 4294967294 is 0xfffffffe. Worse, "qemu-image convert" or direct
> access of the VDI image from qemu involves reads and writes of blocks at
> the bogus block offset 4294967294 within the image file.
>
> Cc: Stefan Weil <address@hidden>
> Cc: Kevin Wolf <address@hidden>
>
> block/vdi.c | 23 ++++++++++++++---------
> 1 files changed, 14 insertions(+), 9 deletions(-)
Good to see this improvement. I recently talked to a CernVM developer
who had issues with vdi images. This may fix the issue they were
seeing.
I think Kevin should take this through the block tree. I won't apply it
to trivial-patches.
Stefan
- [Qemu-devel] [PATCH] Teach block/vdi about "discarded" (no longer allocated) blocks, Eric Sunshine, 2011/10/26
- Re: [Qemu-devel] [PATCH] Teach block/vdi about "discarded" (no longer allocated) blocks, Stefan Weil, 2011/10/26
- Re: [Qemu-devel] [Qemu-trivial] [PATCH] Teach block/vdi about "discarded" (no longer allocated) blocks,
Stefan Hajnoczi <=
- Re: [Qemu-devel] [PATCH] Teach block/vdi about "discarded" (no longer allocated) blocks, Kevin Wolf, 2011/10/27
- Re: [Qemu-devel] [PATCH] Teach block/vdi about "discarded" (no longer allocated) blocks, Stefan Weil, 2011/10/27
- Re: [Qemu-devel] [PATCH] Teach block/vdi about "discarded" (no longer allocated) blocks, Eric Sunshine, 2011/10/27
- Re: [Qemu-devel] [PATCH] Teach block/vdi about "discarded" (no longer allocated) blocks, Kevin Wolf, 2011/10/28
- Re: [Qemu-devel] [PATCH] Teach block/vdi about "discarded" (no longer allocated) blocks, Eric Sunshine, 2011/10/28
- Re: [Qemu-devel] [PATCH] Teach block/vdi about "discarded" (no longer allocated) blocks, Kevin Wolf, 2011/10/28
- Re: [Qemu-devel] [PATCH] Teach block/vdi about "discarded" (no longer allocated) blocks, Stefan Weil, 2011/10/28