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authorJeff Cody <jcody@redhat.com>2013-04-29 14:48:19 -0400
committerStefan Hajnoczi <stefanha@redhat.com>2013-05-03 10:31:58 +0200
commit059e2fbbca484a68ac7fd99d1d76409294551586 (patch)
treed9aec6880a4f9e763925becbfbb5662ecac562cf
parente8d4e5ffdb015959551726a5700c19b5d772ada4 (diff)
downloadhqemu-059e2fbbca484a68ac7fd99d1d76409294551586.zip
hqemu-059e2fbbca484a68ac7fd99d1d76409294551586.tar.gz
block: add read-only support to VHDX image format.
This adds in read-only support to the VHDX image format. This supports reads for fixed-size, and dynamic sized VHDX images. Differencing files are still unsupported. The image must be opened without BDRV_O_RDWR set, because we do not yet update the headers. I.e., pass 'readonly=on' in the drive image options from the QEMU commandline. Signed-off-by: Jeff Cody <jcody@redhat.com> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
-rw-r--r--block/vhdx.c123
1 files changed, 121 insertions, 2 deletions
diff --git a/block/vhdx.c b/block/vhdx.c
index 0ee10a7..e9704b1 100644
--- a/block/vhdx.c
+++ b/block/vhdx.c
@@ -114,6 +114,17 @@ typedef struct VHDXMetadataEntries {
} VHDXMetadataEntries;
+typedef struct VHDXSectorInfo {
+ uint32_t bat_idx; /* BAT entry index */
+ uint32_t sectors_avail; /* sectors available in payload block */
+ uint32_t bytes_left; /* bytes left in the block after data to r/w */
+ uint32_t bytes_avail; /* bytes available in payload block */
+ uint64_t file_offset; /* absolute offset in bytes, in file */
+ uint64_t block_offset; /* block offset, in bytes */
+} VHDXSectorInfo;
+
+
+
typedef struct BDRVVHDXState {
CoMutex lock;
@@ -792,7 +803,7 @@ static int vhdx_open(BlockDriverState *bs, QDict *options, int flags)
goto fail;
}
- /* TODO: differencing files, read, write */
+ /* TODO: differencing files, write */
return 0;
fail:
@@ -810,10 +821,118 @@ static int vhdx_reopen_prepare(BDRVReopenState *state,
}
+/*
+ * Perform sector to block offset translations, to get various
+ * sector and file offsets into the image. See VHDXSectorInfo
+ */
+static void vhdx_block_translate(BDRVVHDXState *s, int64_t sector_num,
+ int nb_sectors, VHDXSectorInfo *sinfo)
+{
+ uint32_t block_offset;
+
+ sinfo->bat_idx = sector_num >> s->sectors_per_block_bits;
+ /* effectively a modulo - this gives us the offset into the block
+ * (in sector sizes) for our sector number */
+ block_offset = sector_num - (sinfo->bat_idx << s->sectors_per_block_bits);
+ /* the chunk ratio gives us the interleaving of the sector
+ * bitmaps, so we need to advance our page block index by the
+ * sector bitmaps entry number */
+ sinfo->bat_idx += sinfo->bat_idx >> s->chunk_ratio_bits;
+
+ /* the number of sectors we can read/write in this cycle */
+ sinfo->sectors_avail = s->sectors_per_block - block_offset;
+
+ sinfo->bytes_left = sinfo->sectors_avail << s->logical_sector_size_bits;
+
+ if (sinfo->sectors_avail > nb_sectors) {
+ sinfo->sectors_avail = nb_sectors;
+ }
+
+ sinfo->bytes_avail = sinfo->sectors_avail << s->logical_sector_size_bits;
+
+ sinfo->file_offset = s->bat[sinfo->bat_idx] >> VHDX_BAT_FILE_OFF_BITS;
+
+ sinfo->block_offset = block_offset << s->logical_sector_size_bits;
+
+ /* The file offset must be past the header section, so must be > 0 */
+ if (sinfo->file_offset == 0) {
+ return;
+ }
+
+ /* block offset is the offset in vhdx logical sectors, in
+ * the payload data block. Convert that to a byte offset
+ * in the block, and add in the payload data block offset
+ * in the file, in bytes, to get the final read address */
+
+ sinfo->file_offset <<= 20; /* now in bytes, rather than 1MB units */
+ sinfo->file_offset += sinfo->block_offset;
+}
+
+
+
static coroutine_fn int vhdx_co_readv(BlockDriverState *bs, int64_t sector_num,
int nb_sectors, QEMUIOVector *qiov)
{
- return -ENOTSUP;
+ BDRVVHDXState *s = bs->opaque;
+ int ret = 0;
+ VHDXSectorInfo sinfo;
+ uint64_t bytes_done = 0;
+ QEMUIOVector hd_qiov;
+
+ qemu_iovec_init(&hd_qiov, qiov->niov);
+
+ qemu_co_mutex_lock(&s->lock);
+
+ while (nb_sectors > 0) {
+ /* We are a differencing file, so we need to inspect the sector bitmap
+ * to see if we have the data or not */
+ if (s->params.data_bits & VHDX_PARAMS_HAS_PARENT) {
+ /* not supported yet */
+ ret = -ENOTSUP;
+ goto exit;
+ } else {
+ vhdx_block_translate(s, sector_num, nb_sectors, &sinfo);
+
+ qemu_iovec_reset(&hd_qiov);
+ qemu_iovec_concat(&hd_qiov, qiov, bytes_done, sinfo.bytes_avail);
+
+ /* check the payload block state */
+ switch (s->bat[sinfo.bat_idx] & VHDX_BAT_STATE_BIT_MASK) {
+ case PAYLOAD_BLOCK_NOT_PRESENT: /* fall through */
+ case PAYLOAD_BLOCK_UNDEFINED: /* fall through */
+ case PAYLOAD_BLOCK_UNMAPPED: /* fall through */
+ case PAYLOAD_BLOCK_ZERO:
+ /* return zero */
+ qemu_iovec_memset(&hd_qiov, 0, 0, sinfo.bytes_avail);
+ break;
+ case PAYLOAD_BLOCK_FULL_PRESENT:
+ qemu_co_mutex_unlock(&s->lock);
+ ret = bdrv_co_readv(bs->file,
+ sinfo.file_offset >> BDRV_SECTOR_BITS,
+ sinfo.sectors_avail, &hd_qiov);
+ qemu_co_mutex_lock(&s->lock);
+ if (ret < 0) {
+ goto exit;
+ }
+ break;
+ case PAYLOAD_BLOCK_PARTIALLY_PRESENT:
+ /* we don't yet support difference files, fall through
+ * to error */
+ default:
+ ret = -EIO;
+ goto exit;
+ break;
+ }
+ nb_sectors -= sinfo.sectors_avail;
+ sector_num += sinfo.sectors_avail;
+ bytes_done += sinfo.bytes_avail;
+ }
+ }
+ ret = 0;
+exit:
+ qemu_co_mutex_unlock(&s->lock);
+ qemu_iovec_destroy(&hd_qiov);
+ return ret;
}
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