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block: Introduce bdrv_aligned_preadv() 

This separates the part of bdrv_co_do_readv() that needs to happen
before the request is modified to match the backend alignment, and a
part that needs to be executed afterwards and passes the request to the
BlockDriver.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Wenchao Xia <xiawenc@linux.vnet.ibm.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
This commit is contained in:
Kevin Wolf 2013-12-02 15:07:48 +01:00
parent c25f53b06e
commit d0c7f642f5
1 changed files with 43 additions and 18 deletions
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61
block.c
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@ -2885,26 +2885,24 @@ err:
}
/*
* Handle a read request in coroutine context
* Forwards an already correctly aligned request to the BlockDriver. This
* handles copy on read and zeroing after EOF; any other features must be
* implemented by the caller.
*/
static int coroutine_fn bdrv_co_do_readv(BlockDriverState *bs,
int64_t sector_num, int nb_sectors, QEMUIOVector *qiov,
BdrvRequestFlags flags)
static int coroutine_fn bdrv_aligned_preadv(BlockDriverState *bs,
int64_t offset, unsigned int bytes, QEMUIOVector *qiov, int flags)
{
BlockDriver *drv = bs->drv;
BdrvTrackedRequest req;
int ret;
if (!drv) {
return -ENOMEDIUM;
}
if (bdrv_check_request(bs, sector_num, nb_sectors)) {
return -EIO;
}
int64_t sector_num = offset >> BDRV_SECTOR_BITS;
unsigned int nb_sectors = bytes >> BDRV_SECTOR_BITS;
if (bs->copy_on_read) {
flags |= BDRV_REQ_COPY_ON_READ;
}
assert((offset & (BDRV_SECTOR_SIZE - 1)) == 0);
assert((bytes & (BDRV_SECTOR_SIZE - 1)) == 0);
/* Handle Copy on Read and associated serialisation */
if (flags & BDRV_REQ_COPY_ON_READ) {
bs->copy_on_read_in_flight++;
}
@ -2913,11 +2911,6 @@ static int coroutine_fn bdrv_co_do_readv(BlockDriverState *bs,
wait_for_overlapping_requests(bs, sector_num, nb_sectors);
}
/* throttling disk I/O */
if (bs->io_limits_enabled) {
bdrv_io_limits_intercept(bs, nb_sectors, false);
}
tracked_request_begin(&req, bs, sector_num, nb_sectors, false);
if (flags & BDRV_REQ_COPY_ON_READ) {
@ -2934,6 +2927,7 @@ static int coroutine_fn bdrv_co_do_readv(BlockDriverState *bs,
}
}
/* Forward the request to the BlockDriver */
if (!(bs->zero_beyond_eof && bs->growable)) {
ret = drv->bdrv_co_readv(bs, sector_num, nb_sectors, qiov);
} else {
@ -2974,6 +2968,37 @@ out:
return ret;
}
/*
* Handle a read request in coroutine context
*/
static int coroutine_fn bdrv_co_do_readv(BlockDriverState *bs,
int64_t sector_num, int nb_sectors, QEMUIOVector *qiov,
BdrvRequestFlags flags)
{
BlockDriver *drv = bs->drv;
int ret;
if (!drv) {
return -ENOMEDIUM;
}
if (bdrv_check_request(bs, sector_num, nb_sectors)) {
return -EIO;
}
if (bs->copy_on_read) {
flags |= BDRV_REQ_COPY_ON_READ;
}
/* throttling disk I/O */
if (bs->io_limits_enabled) {
bdrv_io_limits_intercept(bs, nb_sectors, false);
}
ret = bdrv_aligned_preadv(bs, sector_num << BDRV_SECTOR_BITS,
nb_sectors << BDRV_SECTOR_BITS, qiov, flags);
return ret;
}
int coroutine_fn bdrv_co_readv(BlockDriverState *bs, int64_t sector_num,
int nb_sectors, QEMUIOVector *qiov)
{