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vmdk: Fix COW 

When trying to do COW, VMDK wrote the data back to the backing file. This
problem was revealed by the patch that made backing files read-only. This patch
does not only fix the problem, but also simplifies the VMDK code a bit.

This fixes the backing file qemu-iotests cases for VMDK.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Kevin Wolf 2010-04-16 19:28:14 +02:00
parent f2feebbd93
commit c336500df5
1 changed files with 11 additions and 24 deletions
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35
block/vmdk.c
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@ -87,14 +87,6 @@ typedef struct VmdkMetaData {
int valid; int valid;
} VmdkMetaData; } VmdkMetaData;
typedef struct ActiveBDRVState{
BlockDriverState *hd; // active image handler
uint64_t cluster_offset; // current write offset
}ActiveBDRVState;
static ActiveBDRVState activeBDRV;
static int vmdk_probe(const uint8_t *buf, int buf_size, const char *filename) static int vmdk_probe(const uint8_t *buf, int buf_size, const char *filename)
{ {
uint32_t magic; uint32_t magic;
@ -492,30 +484,28 @@ static uint64_t get_cluster_offset(BlockDriverState *bs, VmdkMetaData *m_data,
static int get_whole_cluster(BlockDriverState *bs, uint64_t cluster_offset, static int get_whole_cluster(BlockDriverState *bs, uint64_t cluster_offset,
uint64_t offset, int allocate) uint64_t offset, int allocate)
{ {
uint64_t parent_cluster_offset;
BDRVVmdkState *s = bs->opaque; BDRVVmdkState *s = bs->opaque;
uint8_t whole_grain[s->cluster_sectors*512]; // 128 sectors * 512 bytes each = grain size 64KB uint8_t whole_grain[s->cluster_sectors*512]; // 128 sectors * 512 bytes each = grain size 64KB
// we will be here if it's first write on non-exist grain(cluster). // we will be here if it's first write on non-exist grain(cluster).
// try to read from parent image, if exist // try to read from parent image, if exist
if (bs->backing_hd) { if (bs->backing_hd) {
BDRVVmdkState *ps = bs->backing_hd->opaque; int ret;
if (!vmdk_is_cid_valid(bs)) if (!vmdk_is_cid_valid(bs))
return -1; return -1;
parent_cluster_offset = get_cluster_offset(bs->backing_hd, NULL, ret = bdrv_read(bs->backing_hd, offset >> 9, whole_grain,
offset, allocate); s->cluster_sectors);
if (ret < 0) {
return -1;
}
if (parent_cluster_offset) { //Write grain only into the active image
BDRVVmdkState *act_s = activeBDRV.hd->opaque; ret = bdrv_write(s->hd, cluster_offset, whole_grain,
s->cluster_sectors);
if (bdrv_pread(ps->hd, parent_cluster_offset, whole_grain, ps->cluster_sectors*512) != ps->cluster_sectors*512) if (ret < 0) {
return -1; return -1;
//Write grain only into the active image
if (bdrv_pwrite(act_s->hd, activeBDRV.cluster_offset << 9, whole_grain, sizeof(whole_grain)) != sizeof(whole_grain))
return -1;
} }
} }
return 0; return 0;
@ -601,9 +591,6 @@ static uint64_t get_cluster_offset(BlockDriverState *bs, VmdkMetaData *m_data,
cluster_offset >>= 9; cluster_offset >>= 9;
tmp = cpu_to_le32(cluster_offset); tmp = cpu_to_le32(cluster_offset);
l2_table[l2_index] = tmp; l2_table[l2_index] = tmp;
// Save the active image state
activeBDRV.cluster_offset = cluster_offset;
activeBDRV.hd = bs;
} }
/* First of all we write grain itself, to avoid race condition /* First of all we write grain itself, to avoid race condition
* that may to corrupt the image. * that may to corrupt the image.