haraldwolff/qemu-patch-raspberry4
1
0
Fork 0
Code Issues Pull requests Packages Projects Releases Wiki Activity

qcow2: Support BDRV_REQ_ZERO_WRITE for truncate

Browse source 
If BDRV_REQ_ZERO_WRITE is set and we're extending the image, calling
qcow2_cluster_zeroize() with flags=0 does the right thing: It doesn't
undo any previous preallocation, but just adds the zero flag to all
relevant L2 entries. If an external data file is in use, a write_zeroes
request to the data file is made instead.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Message-Id: <20200424125448.63318-5-kwolf@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Kevin Wolf 2020-04-24 14:54:42 +02:00
parent 8c6242b6f3
commit f01643fb8b
2 changed files with 35 additions and 1 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

2
block/qcow2-cluster.c
View file

@ -1795,7 +1795,7 @@ int qcow2_cluster_zeroize(BlockDriverState *bs, uint64_t offset,
/* Caller must pass aligned values, except at image end */
assert(QEMU_IS_ALIGNED(offset, s->cluster_size));
assert(QEMU_IS_ALIGNED(end_offset, s->cluster_size) ||
end_offset == bs->total_sectors << BDRV_SECTOR_BITS);
end_offset >= bs->total_sectors << BDRV_SECTOR_BITS);
/* The zero flag is only supported by version 3 and newer */
if (s->qcow_version < 3) {

34
block/qcow2.c
View file

@ -1726,6 +1726,7 @@ static int coroutine_fn qcow2_do_open(BlockDriverState *bs, QDict *options,
bs->supported_zero_flags = header.version >= 3 ?
BDRV_REQ_MAY_UNMAP | BDRV_REQ_NO_FALLBACK : 0;
bs->supported_truncate_flags = BDRV_REQ_ZERO_WRITE;
/* Repair image if dirty */
if (!(flags & (BDRV_O_CHECK | BDRV_O_INACTIVE)) && !bs->read_only &&
@ -4214,6 +4215,39 @@ static int coroutine_fn qcow2_co_truncate(BlockDriverState *bs, int64_t offset,
g_assert_not_reached();
}
if ((flags & BDRV_REQ_ZERO_WRITE) && offset > old_length) {
uint64_t zero_start = QEMU_ALIGN_UP(old_length, s->cluster_size);
/*
* Use zero clusters as much as we can. qcow2_cluster_zeroize()
* requires a cluster-aligned start. The end may be unaligned if it is
* at the end of the image (which it is here).
*/
ret = qcow2_cluster_zeroize(bs, zero_start, offset - zero_start, 0);
if (ret < 0) {
error_setg_errno(errp, -ret, "Failed to zero out new clusters");
goto fail;
}
/* Write explicit zeros for the unaligned head */
if (zero_start > old_length) {
uint64_t len = zero_start - old_length;
uint8_t *buf = qemu_blockalign0(bs, len);
QEMUIOVector qiov;
qemu_iovec_init_buf(&qiov, buf, len);
qemu_co_mutex_unlock(&s->lock);
ret = qcow2_co_pwritev_part(bs, old_length, len, &qiov, 0, 0);
qemu_co_mutex_lock(&s->lock);
qemu_vfree(buf);
if (ret < 0) {
error_setg_errno(errp, -ret, "Failed to zero out the new area");
goto fail;
}
}
}
if (prealloc != PREALLOC_MODE_OFF) {
/* Flush metadata before actually changing the image size */
ret = qcow2_write_caches(bs);