block: Add BDRV_REQ_NO_FALLBACK

For qemu-img convert, we want an operation that zeroes out the whole
image if this can be done efficiently, but that returns an error
otherwise so we don't write explicit zeroes and immediately overwrite
them with the real data, potentially doubling the amount of data to be
written.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Acked-by: Eric Blake <eblake@redhat.com>
This commit is contained in:
Kevin Wolf 2019-03-22 13:38:43 +01:00
parent 48ce986096
commit fe0480d629
2 changed files with 17 additions and 2 deletions

View file

@ -83,8 +83,13 @@ typedef enum {
*/
BDRV_REQ_SERIALISING = 0x80,
/* Execute the request only if the operation can be offloaded or otherwise
* be executed efficiently, but return an error instead of using a slow
* fallback. */
BDRV_REQ_NO_FALLBACK = 0x100,
/* Mask of valid flags */
BDRV_REQ_MASK = 0xff,
BDRV_REQ_MASK = 0x1ff,
} BdrvRequestFlags;
typedef struct BlockSizes {