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Re: [Qemu-devel] [PATCH 04/10] qcow: add qcow_co_write_compressed
From: |
Stefan Hajnoczi |
Subject: |
Re: [Qemu-devel] [PATCH 04/10] qcow: add qcow_co_write_compressed |
Date: |
Fri, 27 May 2016 10:45:39 -0700 |
User-agent: |
Mutt/1.6.0 (2016-04-01) |
On Sat, May 14, 2016 at 03:45:52PM +0300, Denis V. Lunev wrote:
> + qemu_co_mutex_lock(&s->lock);
> + cluster_offset = get_cluster_offset(bs, sector_num << 9, 2, out_len, 0,
> 0);
> + qemu_co_mutex_unlock(&s->lock);
> + if (cluster_offset == 0) {
> + ret = -EIO;
> + goto fail;
> + }
> + cluster_offset &= s->cluster_offset_mask;
> +
> + iov = (struct iovec) {
> + .iov_base = out_buf,
> + .iov_len = out_len,
> + };
> + qemu_iovec_init_external(&hd_qiov, &iov, 1);
> + ret = bdrv_co_pwritev(bs->file->bs, cluster_offset, out_len, &hd_qiov,
> 0);
Not sure if this has the same race condition as the qcow2 patch. It
seems that bdrv_getlength() is used to extend the file on a per-sector
basis. That would mean compressed data is not packed inside sectors and
no read-write-modify race condition exists, but I haven't fully audited
get_cluster_offset().
Stefan
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- [Qemu-devel] [PATCH v3 00/10] backup compression, Denis V. Lunev, 2016/05/14
- [Qemu-devel] [PATCH 04/10] qcow: add qcow_co_write_compressed, Denis V. Lunev, 2016/05/14
- Re: [Qemu-devel] [PATCH 04/10] qcow: add qcow_co_write_compressed,
Stefan Hajnoczi <=
- [Qemu-devel] [PATCH 03/10] vmdk: add vmdk_co_write_compressed, Denis V. Lunev, 2016/05/14
- [Qemu-devel] [PATCH 02/10] qcow2: add qcow2_co_write_compressed, Denis V. Lunev, 2016/05/14
- Re: [Qemu-devel] [PATCH 02/10] qcow2: add qcow2_co_write_compressed, Stefan Hajnoczi, 2016/05/27
- Re: [Qemu-devel] [PATCH 02/10] qcow2: add qcow2_co_write_compressed, Pavel Butsykin, 2016/05/30
- Re: [Qemu-devel] [PATCH 02/10] qcow2: add qcow2_co_write_compressed, Pavel Butsykin, 2016/05/30
- Re: [Qemu-devel] [PATCH 02/10] qcow2: add qcow2_co_write_compressed, Eric Blake, 2016/05/31
- Re: [Qemu-devel] [PATCH 02/10] qcow2: add qcow2_co_write_compressed, Denis V. Lunev, 2016/05/31
- Re: [Qemu-devel] [PATCH 02/10] qcow2: add qcow2_co_write_compressed, Eric Blake, 2016/05/31