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block: Introduce bdrv_co_do_preadv() 

Similar to bdrv_pread(), which aligns byte-aligned request to 512 byte
sectors, bdrv_co_do_preadv() takes a byte-aligned request and aligns it
to the alignment specified in bs->request_alignment.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Benoit Canet <benoit@irqsave.net>
This commit is contained in:
Kevin Wolf 2013-12-02 16:09:46 +01:00
parent d0c7f642f5
commit 1b0288ae7f
1 changed files with 58 additions and 6 deletions
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64
block.c
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@ -2971,17 +2971,23 @@ out:
/*
* 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,
static int coroutine_fn bdrv_co_do_preadv(BlockDriverState *bs,
int64_t offset, unsigned int bytes, QEMUIOVector *qiov,
BdrvRequestFlags flags)
{
BlockDriver *drv = bs->drv;
/* TODO Lift BDRV_SECTOR_SIZE restriction in BlockDriver interface */
uint64_t align = MAX(BDRV_SECTOR_SIZE, bs->request_alignment);
uint8_t *head_buf = NULL;
uint8_t *tail_buf = NULL;
QEMUIOVector local_qiov;
bool use_local_qiov = false;
int ret;
if (!drv) {
return -ENOMEDIUM;
}
if (bdrv_check_request(bs, sector_num, nb_sectors)) {
if (bdrv_check_byte_request(bs, offset, bytes)) {
return -EIO;
}
@ -2991,14 +2997,60 @@ static int coroutine_fn bdrv_co_do_readv(BlockDriverState *bs,
/* throttling disk I/O */
if (bs->io_limits_enabled) {
bdrv_io_limits_intercept(bs, nb_sectors, false);
/* TODO Switch to byte granularity */
bdrv_io_limits_intercept(bs, bytes >> BDRV_SECTOR_BITS, false);
}
/* Align read if necessary by padding qiov */
if (offset & (align - 1)) {
head_buf = qemu_blockalign(bs, align);
qemu_iovec_init(&local_qiov, qiov->niov + 2);
qemu_iovec_add(&local_qiov, head_buf, offset & (align - 1));
qemu_iovec_concat(&local_qiov, qiov, 0, qiov->size);
use_local_qiov = true;
bytes += offset & (align - 1);
offset = offset & ~(align - 1);
}
if ((offset + bytes) & (align - 1)) {
if (!use_local_qiov) {
qemu_iovec_init(&local_qiov, qiov->niov + 1);
qemu_iovec_concat(&local_qiov, qiov, 0, qiov->size);
use_local_qiov = true;
}
tail_buf = qemu_blockalign(bs, align);
qemu_iovec_add(&local_qiov, tail_buf,
align - ((offset + bytes) & (align - 1)));
bytes = ROUND_UP(bytes, align);
}
ret = bdrv_aligned_preadv(bs, offset, bytes,
use_local_qiov ? &local_qiov : qiov,
flags);
if (use_local_qiov) {
qemu_iovec_destroy(&local_qiov);
qemu_vfree(head_buf);
qemu_vfree(tail_buf);
}
ret = bdrv_aligned_preadv(bs, sector_num << BDRV_SECTOR_BITS,
nb_sectors << BDRV_SECTOR_BITS, qiov, flags);
return ret;
}
static int coroutine_fn bdrv_co_do_readv(BlockDriverState *bs,
int64_t sector_num, int nb_sectors, QEMUIOVector *qiov,
BdrvRequestFlags flags)
{
if (nb_sectors < 0 || nb_sectors > (UINT_MAX >> BDRV_SECTOR_BITS)) {
return -EINVAL;
}
return bdrv_co_do_preadv(bs, sector_num << BDRV_SECTOR_BITS,
nb_sectors << BDRV_SECTOR_BITS, qiov, flags);
}
int coroutine_fn bdrv_co_readv(BlockDriverState *bs, int64_t sector_num,
int nb_sectors, QEMUIOVector *qiov)
{