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qcow: Switch qcow_co_readv to byte-based calls

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We are gradually moving away from sector-based interfaces, towards
byte-based.  Make the change for the internals of the qcow
driver read function, by iterating over offset/bytes instead of
sector_num/nb_sectors, and with a rename of index_in_cluster and
repurposing of n to track bytes instead of sectors.

A later patch will then switch the qcow driver as a whole over
to byte-based operation.

Signed-off-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Jeff Cody <jcody@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Eric Blake 2018-06-28 15:15:20 -05:00 committed by Kevin Wolf
parent 787993a543
commit a15312b017
1 changed files with 20 additions and 22 deletions
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42
block/qcow.c
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@ -617,13 +617,15 @@ static coroutine_fn int qcow_co_readv(BlockDriverState *bs, int64_t sector_num,
int nb_sectors, QEMUIOVector *qiov)
{
BDRVQcowState *s = bs->opaque;
int index_in_cluster;
int offset_in_cluster;
int ret = 0, n;
uint64_t cluster_offset;
struct iovec hd_iov;
QEMUIOVector hd_qiov;
uint8_t *buf;
void *orig_buf;
int64_t offset = sector_num * BDRV_SECTOR_SIZE;
int64_t bytes = nb_sectors * BDRV_SECTOR_SIZE;
if (qiov->niov > 1) {
buf = orig_buf = qemu_try_blockalign(bs, qiov->size);
@ -637,36 +639,35 @@ static coroutine_fn int qcow_co_readv(BlockDriverState *bs, int64_t sector_num,
qemu_co_mutex_lock(&s->lock);
while (nb_sectors != 0) {
while (bytes != 0) {
/* prepare next request */
ret = get_cluster_offset(bs, sector_num << 9,
0, 0, 0, 0, &cluster_offset);
ret = get_cluster_offset(bs, offset, 0, 0, 0, 0, &cluster_offset);
if (ret < 0) {
break;
}
index_in_cluster = sector_num & (s->cluster_sectors - 1);
n = s->cluster_sectors - index_in_cluster;
if (n > nb_sectors) {
n = nb_sectors;
offset_in_cluster = offset & (s->cluster_size - 1);
n = s->cluster_size - offset_in_cluster;
if (n > bytes) {
n = bytes;
}
if (!cluster_offset) {
if (bs->backing) {
/* read from the base image */
hd_iov.iov_base = (void *)buf;
hd_iov.iov_len = n * 512;
hd_iov.iov_len = n;
qemu_iovec_init_external(&hd_qiov, &hd_iov, 1);
qemu_co_mutex_unlock(&s->lock);
/* qcow2 emits this on bs->file instead of bs->backing */
BLKDBG_EVENT(bs->file, BLKDBG_READ_BACKING_AIO);
ret = bdrv_co_readv(bs->backing, sector_num, n, &hd_qiov);
ret = bdrv_co_preadv(bs->backing, offset, n, &hd_qiov, 0);
qemu_co_mutex_lock(&s->lock);
if (ret < 0) {
break;
}
} else {
/* Note: in this case, no need to wait */
memset(buf, 0, 512 * n);
memset(buf, 0, n);
}
} else if (cluster_offset & QCOW_OFLAG_COMPRESSED) {
/* add AIO support for compressed blocks ? */
@ -674,21 +675,19 @@ static coroutine_fn int qcow_co_readv(BlockDriverState *bs, int64_t sector_num,
ret = -EIO;
break;
}
memcpy(buf,
s->cluster_cache + index_in_cluster * 512, 512 * n);
memcpy(buf, s->cluster_cache + offset_in_cluster, n);
} else {
if ((cluster_offset & 511) != 0) {
ret = -EIO;
break;
}
hd_iov.iov_base = (void *)buf;
hd_iov.iov_len = n * 512;
hd_iov.iov_len = n;
qemu_iovec_init_external(&hd_qiov, &hd_iov, 1);
qemu_co_mutex_unlock(&s->lock);
BLKDBG_EVENT(bs->file, BLKDBG_READ_AIO);
ret = bdrv_co_readv(bs->file,
(cluster_offset >> 9) + index_in_cluster,
n, &hd_qiov);
ret = bdrv_co_preadv(bs->file, cluster_offset + offset_in_cluster,
n, &hd_qiov, 0);
qemu_co_mutex_lock(&s->lock);
if (ret < 0) {
break;
@ -696,8 +695,7 @@ static coroutine_fn int qcow_co_readv(BlockDriverState *bs, int64_t sector_num,
if (bs->encrypted) {
assert(s->crypto);
if (qcrypto_block_decrypt(s->crypto,
sector_num * BDRV_SECTOR_SIZE, buf,
n * BDRV_SECTOR_SIZE, NULL) < 0) {
offset, buf, n, NULL) < 0) {
ret = -EIO;
break;
}
@ -705,9 +703,9 @@ static coroutine_fn int qcow_co_readv(BlockDriverState *bs, int64_t sector_num,
}
ret = 0;
nb_sectors -= n;
sector_num += n;
buf += n * 512;
bytes -= n;
offset += n;
buf += n;
}
qemu_co_mutex_unlock(&s->lock);