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qcow2: Zero write support

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Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Kevin Wolf 2012-03-20 15:12:58 +01:00
parent ab3a32ad5e
commit 621f058940
4 changed files with 105 additions and 3 deletions
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14
block.c
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@ -80,6 +80,8 @@ static BlockDriverAIOCB *bdrv_co_aio_rw_vector(BlockDriverState *bs,
void *opaque,
bool is_write);
static void coroutine_fn bdrv_co_do_rw(void *opaque);
static int coroutine_fn bdrv_co_do_write_zeroes(BlockDriverState *bs,
int64_t sector_num, int nb_sectors);
static bool bdrv_exceed_bps_limits(BlockDriverState *bs, int nb_sectors,
bool is_write, double elapsed_time, uint64_t *wait);
@ -1708,8 +1710,8 @@ static int coroutine_fn bdrv_co_do_copy_on_readv(BlockDriverState *bs,
if (drv->bdrv_co_write_zeroes &&
buffer_is_zero(bounce_buffer, iov.iov_len)) {
ret = drv->bdrv_co_write_zeroes(bs, cluster_sector_num,
cluster_nb_sectors);
ret = bdrv_co_do_write_zeroes(bs, cluster_sector_num,
cluster_nb_sectors);
} else {
ret = drv->bdrv_co_writev(bs, cluster_sector_num, cluster_nb_sectors,
&bounce_qiov);
@ -1819,9 +1821,15 @@ static int coroutine_fn bdrv_co_do_write_zeroes(BlockDriverState *bs,
struct iovec iov;
int ret;
/* TODO Emulate only part of misaligned requests instead of letting block
* drivers return -ENOTSUP and emulate everything */
/* First try the efficient write zeroes operation */
if (drv->bdrv_co_write_zeroes) {
return drv->bdrv_co_write_zeroes(bs, sector_num, nb_sectors);
ret = drv->bdrv_co_write_zeroes(bs, sector_num, nb_sectors);
if (ret != -ENOTSUP) {
return ret;
}
}
/* Fall back to bounce buffer if write zeroes is unsupported */