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block: Don't enforce 512 byte minimum alignment 

If block drivers say that they can do an alignment < 512 bytes, let's
just suppose they mean it. raw-posix used to be an offender with respect
to this, but it can actually deal with byte-aligned requests now.

The default is still 512 bytes for any drivers that only implement
sector-based interfaces, but it is 1 now for drivers that implement
.bdrv_co_preadv.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
This commit is contained in:
Kevin Wolf 2016-06-03 16:45:44 +02:00
parent 9d52aa3c38
commit 23b0d9fb1d
2 changed files with 4 additions and 6 deletions
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2
block.c
View File

@ -937,7 +937,7 @@ static int bdrv_open_common(BlockDriverState *bs, BdrvChild *file,
goto fail_opts;
}
bs->request_alignment = 512;
bs->request_alignment = drv->bdrv_co_preadv ? 1 : 512;
bs->zero_beyond_eof = true;
bs->read_only = !(bs->open_flags & BDRV_O_RDWR);

8
block/io.c
View File

@ -1052,8 +1052,7 @@ int coroutine_fn bdrv_co_preadv(BlockDriverState *bs,
BlockDriver *drv = bs->drv;
BdrvTrackedRequest req;
/* TODO Lift BDRV_SECTOR_SIZE restriction in BlockDriver interface */
uint64_t align = MAX(BDRV_SECTOR_SIZE, bs->request_alignment);
uint64_t align = bs->request_alignment;
uint8_t *head_buf = NULL;
uint8_t *tail_buf = NULL;
QEMUIOVector local_qiov;
@ -1305,7 +1304,7 @@ static int coroutine_fn bdrv_co_do_zero_pwritev(BlockDriverState *bs,
uint8_t *buf = NULL;
QEMUIOVector local_qiov;
struct iovec iov;
uint64_t align = MAX(BDRV_SECTOR_SIZE, bs->request_alignment);
uint64_t align = bs->request_alignment;
unsigned int head_padding_bytes, tail_padding_bytes;
int ret = 0;
@ -1392,8 +1391,7 @@ int coroutine_fn bdrv_co_pwritev(BlockDriverState *bs,
BdrvRequestFlags flags)
{
BdrvTrackedRequest req;
/* TODO Lift BDRV_SECTOR_SIZE restriction in BlockDriver interface */
uint64_t align = MAX(BDRV_SECTOR_SIZE, bs->request_alignment);
uint64_t align = bs->request_alignment;
uint8_t *head_buf = NULL;
uint8_t *tail_buf = NULL;
QEMUIOVector local_qiov;