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block: Byte-based bdrv_co_do_copy_on_readv()

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In a first step to convert the common I/O path to work on bytes rather
than sectors, this converts the copy-on-read logic that is used by
bdrv_aligned_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 2016-06-02 11:41:52 +02:00
parent 8c0dcbc4ad
commit 244483e64e
4 changed files with 52 additions and 33 deletions
Download patch file Download diff file Expand all files Collapse all files

63
block/io.c
View file

@ -404,12 +404,12 @@ static void mark_request_serialising(BdrvTrackedRequest *req, uint64_t align)
}
/**
* Round a region to cluster boundaries
* Round a region to cluster boundaries (sector-based)
*/
void bdrv_round_to_clusters(BlockDriverState *bs,
int64_t sector_num, int nb_sectors,
int64_t *cluster_sector_num,
int *cluster_nb_sectors)
void bdrv_round_sectors_to_clusters(BlockDriverState *bs,
int64_t sector_num, int nb_sectors,
int64_t *cluster_sector_num,
int *cluster_nb_sectors)
{
BlockDriverInfo bdi;
@ -424,6 +424,26 @@ void bdrv_round_to_clusters(BlockDriverState *bs,
}
}
/**
* Round a region to cluster boundaries
*/
void bdrv_round_to_clusters(BlockDriverState *bs,
int64_t offset, unsigned int bytes,
int64_t *cluster_offset,
unsigned int *cluster_bytes)
{
BlockDriverInfo bdi;
if (bdrv_get_info(bs, &bdi) < 0 || bdi.cluster_size == 0) {
*cluster_offset = offset;
*cluster_bytes = bytes;
} else {
int64_t c = bdi.cluster_size;
*cluster_offset = QEMU_ALIGN_DOWN(offset, c);
*cluster_bytes = QEMU_ALIGN_UP(offset - *cluster_offset + bytes, c);
}
}
static int bdrv_get_cluster_size(BlockDriverState *bs)
{
BlockDriverInfo bdi;
@ -865,7 +885,7 @@ emulate_flags:
}
static int coroutine_fn bdrv_co_do_copy_on_readv(BlockDriverState *bs,
int64_t sector_num, int nb_sectors, QEMUIOVector *qiov)
int64_t offset, unsigned int bytes, QEMUIOVector *qiov)
{
/* Perform I/O through a temporary buffer so that users who scribble over
* their read buffer while the operation is in progress do not end up
@ -877,21 +897,20 @@ static int coroutine_fn bdrv_co_do_copy_on_readv(BlockDriverState *bs,
BlockDriver *drv = bs->drv;
struct iovec iov;
QEMUIOVector bounce_qiov;
int64_t cluster_sector_num;
int cluster_nb_sectors;
int64_t cluster_offset;
unsigned int cluster_bytes;
size_t skip_bytes;
int ret;
/* Cover entire cluster so no additional backing file I/O is required when
* allocating cluster in the image file.
*/
bdrv_round_to_clusters(bs, sector_num, nb_sectors,
&cluster_sector_num, &cluster_nb_sectors);
bdrv_round_to_clusters(bs, offset, bytes, &cluster_offset, &cluster_bytes);
trace_bdrv_co_do_copy_on_readv(bs, sector_num, nb_sectors,
cluster_sector_num, cluster_nb_sectors);
trace_bdrv_co_do_copy_on_readv(bs, offset, bytes,
cluster_offset, cluster_bytes);
iov.iov_len = cluster_nb_sectors * BDRV_SECTOR_SIZE;
iov.iov_len = cluster_bytes;
iov.iov_base = bounce_buffer = qemu_try_blockalign(bs, iov.iov_len);
if (bounce_buffer == NULL) {
ret = -ENOMEM;
@ -900,8 +919,7 @@ static int coroutine_fn bdrv_co_do_copy_on_readv(BlockDriverState *bs,
qemu_iovec_init_external(&bounce_qiov, &iov, 1);
ret = bdrv_driver_preadv(bs, cluster_sector_num * BDRV_SECTOR_SIZE,
cluster_nb_sectors * BDRV_SECTOR_SIZE,
ret = bdrv_driver_preadv(bs, cluster_offset, cluster_bytes,
&bounce_qiov, 0);
if (ret < 0) {
goto err;
@ -909,16 +927,12 @@ static int coroutine_fn bdrv_co_do_copy_on_readv(BlockDriverState *bs,
if (drv->bdrv_co_pwrite_zeroes &&
buffer_is_zero(bounce_buffer, iov.iov_len)) {
ret = bdrv_co_do_pwrite_zeroes(bs,
cluster_sector_num * BDRV_SECTOR_SIZE,
cluster_nb_sectors * BDRV_SECTOR_SIZE,
0);
ret = bdrv_co_do_pwrite_zeroes(bs, cluster_offset, cluster_bytes, 0);
} else {
/* This does not change the data on the disk, it is not necessary
* to flush even in cache=writethrough mode.
*/
ret = bdrv_driver_pwritev(bs, cluster_sector_num * BDRV_SECTOR_SIZE,
cluster_nb_sectors * BDRV_SECTOR_SIZE,
ret = bdrv_driver_pwritev(bs, cluster_offset, cluster_bytes,
&bounce_qiov, 0);
}
@ -930,9 +944,8 @@ static int coroutine_fn bdrv_co_do_copy_on_readv(BlockDriverState *bs,
goto err;
}
skip_bytes = (sector_num - cluster_sector_num) * BDRV_SECTOR_SIZE;
qemu_iovec_from_buf(qiov, 0, bounce_buffer + skip_bytes,
nb_sectors * BDRV_SECTOR_SIZE);
skip_bytes = offset - cluster_offset;
qemu_iovec_from_buf(qiov, 0, bounce_buffer + skip_bytes, bytes);
err:
qemu_vfree(bounce_buffer);
@ -982,7 +995,7 @@ static int coroutine_fn bdrv_aligned_preadv(BlockDriverState *bs,
}
if (!ret || pnum != nb_sectors) {
ret = bdrv_co_do_copy_on_readv(bs, sector_num, nb_sectors, qiov);
ret = bdrv_co_do_copy_on_readv(bs, offset, bytes, qiov);
goto out;
}
}