Am 31.05.2016 um 11:15 hat Denis V. Lunev geschrieben:
> From: Pavel Butsykin <pbutsy...@virtuozzo.com>
>
> Added implementation of the qcow2_co_write_compressed function that
> will allow us to safely use compressed writes for the qcow2 from running VMs.
>
> Signed-off-by: Pavel Butsykin <pbutsy...@virtuozzo.com>
> Signed-off-by: Denis V. Lunev <d...@openvz.org>
> CC: Jeff Cody <jc...@redhat.com>
> CC: Markus Armbruster <arm...@redhat.com>
> CC: Eric Blake <ebl...@redhat.com>
> CC: John Snow <js...@redhat.com>
> CC: Stefan Hajnoczi <stefa...@redhat.com>
> CC: Kevin Wolf <kw...@redhat.com>
> ---
> block/qcow2.c | 89
> ++++++++++++++++++++++++++++++++++-------------------------
> 1 file changed, 52 insertions(+), 37 deletions(-)
>
> diff --git a/block/qcow2.c b/block/qcow2.c
> index c9306a7..38caa66 100644
> --- a/block/qcow2.c
> +++ b/block/qcow2.c
> @@ -2535,13 +2535,16 @@ static int qcow2_truncate(BlockDriverState *bs,
> int64_t offset)
>
> /* XXX: put compressed sectors first, then all the cluster aligned
> tables to avoid losing bytes in alignment */
> -static int qcow2_write_compressed(BlockDriverState *bs, int64_t sector_num,
> - const uint8_t *buf, int nb_sectors)
> +static coroutine_fn int
> +qcow2_co_write_compressed(BlockDriverState *bs, int64_t sector_num,
> + int nb_sectors, QEMUIOVector *qiov)
> {
> BDRVQcow2State *s = bs->opaque;
> + QEMUIOVector hd_qiov;
> + struct iovec iov;
> z_stream strm;
> int ret, out_len;
> - uint8_t *out_buf;
> + uint8_t *buf, *out_buf;
> uint64_t cluster_offset;
>
> if (nb_sectors == 0) {
> @@ -2551,29 +2554,25 @@ static int qcow2_write_compressed(BlockDriverState
> *bs, int64_t sector_num,
> return bdrv_truncate(bs->file->bs, cluster_offset);
> }
>
> + buf = qemu_blockalign(bs, s->cluster_size);
> if (nb_sectors != s->cluster_sectors) {
> - ret = -EINVAL;
> -
> - /* Zero-pad last write if image size is not cluster aligned */
> - if (sector_num + nb_sectors == bs->total_sectors &&
> - nb_sectors < s->cluster_sectors) {
> - uint8_t *pad_buf = qemu_blockalign(bs, s->cluster_size);
> - memset(pad_buf, 0, s->cluster_size);
> - memcpy(pad_buf, buf, nb_sectors * BDRV_SECTOR_SIZE);
> - ret = qcow2_write_compressed(bs, sector_num,
> - pad_buf, s->cluster_sectors);
> - qemu_vfree(pad_buf);
> + if (nb_sectors > s->cluster_sectors ||
> + sector_num + nb_sectors != bs->total_sectors)
> + {
> + qemu_vfree(buf);
> + return -EINVAL;
> }
> - return ret;
> + /* Zero-pad last write if image size is not cluster aligned */
> + memset(buf, 0, s->cluster_size);
> }
> + qemu_iovec_to_buf(qiov, 0, buf, qiov->size);
This looks less related to the new interface, but more like an unrelated
(but still worthwhile) cleanup to avoid the recursion.
Can we separate this out as a cleanup patch before this one?
Also, the last parameter of qemu_iovec_to_buf() should be
s->cluster_size, it's the buffer size and not the qiov size.
Additionally, we may want to assert(qiov->size == s->cluster_size).
> out_buf = g_malloc(s->cluster_size + (s->cluster_size / 1000) + 128);
>
> /* best compression, small window, no zlib header */
> memset(&strm, 0, sizeof(strm));
> - ret = deflateInit2(&strm, Z_DEFAULT_COMPRESSION,
> - Z_DEFLATED, -12,
> - 9, Z_DEFAULT_STRATEGY);
> + ret = deflateInit2(&strm, Z_DEFAULT_COMPRESSION, Z_DEFLATED,
> + -12, 9, Z_DEFAULT_STRATEGY);
Unrelated reformatting? Let's drop this, so the semantic changes in the
patch become more visible.
> if (ret != 0) {
> ret = -EINVAL;
> goto fail;
> @@ -2595,34 +2594,50 @@ static int qcow2_write_compressed(BlockDriverState
> *bs, int64_t sector_num,
> deflateEnd(&strm);
>
> if (ret != Z_STREAM_END || out_len >= s->cluster_size) {
> + iov = (struct iovec) {
> + .iov_base = buf,
> + .iov_len = out_len,
> + };
> + qemu_iovec_init_external(&hd_qiov, &iov, 1);
> /* could not compress: write normal cluster */
> - ret = bdrv_write(bs, sector_num, buf, s->cluster_sectors);
> + ret = qcow2_co_writev(bs, sector_num, s->cluster_sectors, &hd_qiov);
Now that it's qcow2_co_pwritev(), you can probably just use the existing
qiov.
> if (ret < 0) {
> goto fail;
> }
> - } else {
> - cluster_offset = qcow2_alloc_compressed_cluster_offset(bs,
> - sector_num << 9, out_len);
> - if (!cluster_offset) {
> - ret = -EIO;
> - goto fail;
> - }
> - cluster_offset &= s->cluster_offset_mask;
> + goto success;
> + }
>
> - ret = qcow2_pre_write_overlap_check(bs, 0, cluster_offset, out_len);
> - if (ret < 0) {
> - goto fail;
> - }
> + qemu_co_mutex_lock(&s->lock);
> + cluster_offset = \
That backslash isn't necessary.
> + qcow2_alloc_compressed_cluster_offset(bs, sector_num << 9, out_len);
> + if (!cluster_offset) {
> + qemu_co_mutex_unlock(&s->lock);
> + ret = -EIO;
> + goto fail;
> + }
> + cluster_offset &= s->cluster_offset_mask;
Kevin
