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block: Read only one sector for format probing

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The only image format driver that even potentially accesses anything
after 512 bytes in its bdrv_probe() implementation is VMDK, which reads
a plain-text descriptor file. In practice, the field it's looking for
seems to come first and will be well within the first 512 bytes, too.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Message-id: 1416497234-29880-7-git-send-email-kwolf@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Kevin Wolf 2014-11-20 16:27:11 +01:00
parent c6684249fd
commit 7cddd3728e
2 changed files with 5 additions and 3 deletions
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6
block.c
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@ -654,8 +654,8 @@ BlockDriver *bdrv_find_protocol(const char *filename,
* we do it anyway for backward compatibility.
*
* @buf contains the image's first @buf_size bytes.
* @buf_size is the buffer size in bytes (generally 2048, but can be smaller
* if the image file is smaller)
* @buf_size is the buffer size in bytes (generally BLOCK_PROBE_BUF_SIZE,
* but can be smaller if the image file is smaller)
* @filename is its filename.
*
* For all block drivers, call the bdrv_probe() method to get its
@ -685,7 +685,7 @@ static int find_image_format(BlockDriverState *bs, const char *filename,
BlockDriver **pdrv, Error **errp)
{
BlockDriver *drv;
uint8_t buf[2048];
uint8_t buf[BLOCK_PROBE_BUF_SIZE];
int ret = 0;
/* Return the raw BlockDriver * to scsi-generic devices or empty drives */

2
include/block/block_int.h
View File

@ -57,6 +57,8 @@
#define BLOCK_OPT_REDUNDANCY "redundancy"
#define BLOCK_OPT_NOCOW "nocow"
#define BLOCK_PROBE_BUF_SIZE 512
typedef struct BdrvTrackedRequest {
BlockDriverState *bs;
int64_t offset;