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block/parallels: add backing support to readv/writev

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Since parallels format supports backing files, refine
readv/writev (allocate_clusters) to redirect read/write requests
to a backing file (if cluster is not available in the current bs).

Signed-off-by: Edgar Kaziakhmedov <edgar.kaziakhmedov@virtuozzo.com>
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Signed-off-by: Denis V. Lunev <den@openvz.org>
Signed-off-by: Klim Kireev <klim.kireev@virtuozzo.com>
Message-id: 20180112090122.1702-6-klim.kireev@virtuozzo.com
CC: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
This commit is contained in:
Edgar Kaziakhmedov 2018-01-12 12:01:22 +03:00 committed by Stefan Hajnoczi
parent 908b1c848e
commit bcbb3866da
1 changed files with 45 additions and 7 deletions
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52
block/parallels.c
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@ -142,6 +142,7 @@ static int64_t block_status(BDRVParallelsState *s, int64_t sector_num,
static int64_t allocate_clusters(BlockDriverState *bs, int64_t sector_num,
int nb_sectors, int *pnum)
{
int ret;
BDRVParallelsState *s = bs->opaque;
int64_t pos, space, idx, to_allocate, i, len;
@ -170,7 +171,6 @@ static int64_t allocate_clusters(BlockDriverState *bs, int64_t sector_num,
return len;
}
if (s->data_end + space > (len >> BDRV_SECTOR_BITS)) {
int ret;
space += s->prealloc_size;
if (s->prealloc_mode == PRL_PREALLOC_MODE_FALLOCATE) {
ret = bdrv_pwrite_zeroes(bs->file,
@ -186,6 +186,37 @@ static int64_t allocate_clusters(BlockDriverState *bs, int64_t sector_num,
}
}
/* Try to read from backing to fill empty clusters
* FIXME: 1. previous write_zeroes may be redundant
* 2. most of data we read from backing will be rewritten by
* parallels_co_writev. On aligned-to-cluster write we do not need
* this read at all.
* 3. it would be good to combine write of data from backing and new
* data into one write call */
if (bs->backing) {
int64_t nb_cow_sectors = to_allocate * s->tracks;
int64_t nb_cow_bytes = nb_cow_sectors << BDRV_SECTOR_BITS;
QEMUIOVector qiov;
struct iovec iov = {
.iov_len = nb_cow_bytes,
.iov_base = qemu_blockalign(bs, nb_cow_bytes)
};
qemu_iovec_init_external(&qiov, &iov, 1);
ret = bdrv_co_readv(bs->backing, idx * s->tracks, nb_cow_sectors,
&qiov);
if (ret < 0) {
qemu_vfree(iov.iov_base);
return ret;
}
ret = bdrv_co_writev(bs->file, s->data_end, nb_cow_sectors, &qiov);
qemu_vfree(iov.iov_base);
if (ret < 0) {
return ret;
}
}
for (i = 0; i < to_allocate; i++) {
s->bat_bitmap[idx + i] = cpu_to_le32(s->data_end / s->off_multiplier);
s->data_end += s->tracks;
@ -309,12 +340,19 @@ static coroutine_fn int parallels_co_readv(BlockDriverState *bs,
nbytes = n << BDRV_SECTOR_BITS;
if (position < 0) {
qemu_iovec_memset(qiov, bytes_done, 0, nbytes);
} else {
qemu_iovec_reset(&hd_qiov);
qemu_iovec_concat(&hd_qiov, qiov, bytes_done, nbytes);
qemu_iovec_reset(&hd_qiov);
qemu_iovec_concat(&hd_qiov, qiov, bytes_done, nbytes);
if (position < 0) {
if (bs->backing) {
ret = bdrv_co_readv(bs->backing, sector_num, n, &hd_qiov);
if (ret < 0) {
break;
}
} else {
qemu_iovec_memset(&hd_qiov, 0, 0, nbytes);
}
} else {
ret = bdrv_co_readv(bs->file, position, n, &hd_qiov);
if (ret < 0) {
break;
@ -748,7 +786,7 @@ static BlockDriver bdrv_parallels = {
.bdrv_co_flush_to_os = parallels_co_flush_to_os,
.bdrv_co_readv = parallels_co_readv,
.bdrv_co_writev = parallels_co_writev,
.supports_backing = true,
.bdrv_create = parallels_create,
.bdrv_check = parallels_check,
.create_opts = &parallels_create_opts,