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Re: [Qemu-block] [PATCH 06/22] qcow2: add dirty bitmaps extension
From: |
Max Reitz |
Subject: |
Re: [Qemu-block] [PATCH 06/22] qcow2: add dirty bitmaps extension |
Date: |
Sat, 1 Oct 2016 16:46:40 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.3.0 |
On 30.09.2016 12:53, Vladimir Sementsov-Ogievskiy wrote:
> Add dirty bitmap extension as specified in docs/specs/qcow2.txt.
> For now, just mirror extension header into Qcow2 state and check
> constraints.
>
> For now, disable image resize if it has bitmaps. It will be fixed later.
>
> Signed-off-by: Vladimir Sementsov-Ogievskiy <address@hidden>
> ---
> block/qcow2.c | 83
> +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
> block/qcow2.h | 4 +++
> 2 files changed, 87 insertions(+)
>
> diff --git a/block/qcow2.c b/block/qcow2.c
> index c079aa8..08c4ef9 100644
> --- a/block/qcow2.c
> +++ b/block/qcow2.c
[...]
> @@ -162,6 +164,62 @@ static int qcow2_read_extensions(BlockDriverState *bs,
> uint64_t start_offset,
> }
> break;
>
> + case QCOW2_EXT_MAGIC_DIRTY_BITMAPS:
> + ret = bdrv_pread(bs->file, offset, &bitmaps_ext, ext.len);
Overflows with ext.len > sizeof(bitmaps_ext).
(ext.len < sizeof(bitmaps_ext) is also wrong, but less dramatically so.)
> + if (ret < 0) {
> + error_setg_errno(errp, -ret, "ERROR: bitmaps_ext: "
> + "Could not read ext header");
> + return ret;
> + }
> +
> + if (bitmaps_ext.reserved32 != 0) {
> + error_setg_errno(errp, -ret, "ERROR: bitmaps_ext: "
> + "Reserved field is not zero.");
Please drop the full stop at the end.
> + return -EINVAL;
> + }
> +
> + be32_to_cpus(&bitmaps_ext.nb_bitmaps);
> + be64_to_cpus(&bitmaps_ext.bitmap_directory_size);
> + be64_to_cpus(&bitmaps_ext.bitmap_directory_offset);
> +
> + if (bitmaps_ext.nb_bitmaps > QCOW_MAX_DIRTY_BITMAPS) {
> + error_setg(errp, "ERROR: bitmaps_ext: "
> + "too many dirty bitmaps");
> + return -EINVAL;
> + }
> +
> + if (bitmaps_ext.nb_bitmaps == 0) {
> + error_setg(errp, "ERROR: bitmaps_ext: "
> + "found bitmaps extension with zero
> bitmaps");
> + return -EINVAL;
> + }
> +
> + if (bitmaps_ext.bitmap_directory_offset & (s->cluster_size - 1))
> {
> + error_setg(errp, "ERROR: bitmaps_ext: "
> + "wrong dirty bitmap directory offset");
s/wrong/invalid/
> + return -EINVAL;
> + }
> +
> + if (bitmaps_ext.bitmap_directory_size >
> + QCOW_MAX_DIRTY_BITMAP_DIRECTORY_SIZE) {
> + error_setg(errp, "ERROR: bitmaps_ext: "
> + "too large dirty bitmap directory");
> + return -EINVAL;
> + }
> +
> + s->nb_bitmaps = bitmaps_ext.nb_bitmaps;
> + s->bitmap_directory_offset =
> + bitmaps_ext.bitmap_directory_offset;
> + s->bitmap_directory_size =
> + bitmaps_ext.bitmap_directory_size;
> +
> +#ifdef DEBUG_EXT
> + printf("Qcow2: Got dirty bitmaps extension:"
> + " offset=%" PRIu64 " nb_bitmaps=%" PRIu32 "\n",
> + s->bitmap_directory_offset, s->nb_bitmaps);
> +#endif
> + break;
> +
> default:
> /* unknown magic - save it in case we need to rewrite the header
> */
> {
[...]
> @@ -2509,6 +2585,13 @@ static int qcow2_truncate(BlockDriverState *bs,
> int64_t offset)
> return -ENOTSUP;
> }
>
> + /* cannot proceed if image has bitmaps */
> + if (s->nb_bitmaps) {
> + /* FIXME */
I'd call it a TODO, but that's probably a matter of taste.
> + error_report("Can't resize an image which has bitmaps");
> + return -ENOTSUP;
> + }
> +
> /* shrinking is currently not supported */
> if (offset < bs->total_sectors * 512) {
> error_report("qcow2 doesn't support shrinking images yet");
Max
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