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Re: [Qemu-devel] [PATCH] raw-posix: Fix .bdrv_co_get_block_status() for
From: |
Wen Congyang |
Subject: |
Re: [Qemu-devel] [PATCH] raw-posix: Fix .bdrv_co_get_block_status() for unaligned image size |
Date: |
Tue, 9 Jun 2015 17:47:36 +0800 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.7.0 |
On 06/09/2015 04:55 PM, Kevin Wolf wrote:
> Image files with an unaligned image size have a final hole that starts
> at EOF, i.e. in the middle of a sector. Currently, *pnum == 0 is
> returned when checking the status of this sector. In qemu-img, this
> triggers an assertion failure.
>
> In order to fix this, one type for the sector that contains EOF must be
> found. Treating a hole as data is safe, so this patch rounds the
> calculated number of data sectors up, so that a partial sector at EOF is
> treated as a full data sector.
>
> This fixes https://bugzilla.redhat.com/show_bug.cgi?id=1229394
>
> Signed-off-by: Kevin Wolf <address@hidden>
> ---
> block/raw-posix.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/block/raw-posix.c b/block/raw-posix.c
> index 2990e95..44ade8c 100644
> --- a/block/raw-posix.c
> +++ b/block/raw-posix.c
> @@ -1848,8 +1848,9 @@ static int64_t coroutine_fn
> raw_co_get_block_status(BlockDriverState *bs,
> *pnum = nb_sectors;
> ret = BDRV_BLOCK_DATA;
> } else if (data == start) {
> - /* On a data extent, compute sectors to the end of the extent. */
> - *pnum = MIN(nb_sectors, (hole - start) / BDRV_SECTOR_SIZE);
> + /* On a data extent, compute sectors to the end of the extent,
> + * possibly including a partial sector at EOF. */
Not only for EOF. If the hole and start are in the same sector, (hole - start)
/ BDRV_SECTOR_SIZE
will be 0
> + *pnum = MIN(nb_sectors, DIV_ROUND_UP(hole - start,
> BDRV_SECTOR_SIZE));
> ret = BDRV_BLOCK_DATA;
> } else {
> /* On a hole, compute sectors to the beginning of the next extent.
> */
>
So, if start is hole, data and start are in the same sector, (data - start) /
BDRV_SECTOR_SIZE
will be 0, you also need to fix it here.
Thanks
Wen Congyang