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vmdk: add support for “zeroed‐grain” GTE 

Introduced support for zeroed-grain GTE, as specified in Virtual Disk
Format 5.0[1].

    Recent VMware hosted platform products support a new “zeroed‐grain”
    grain table entry (GTE). The zeroed‐grain GTE returns all zeros on
    read.  In other words, the zeroed‐grain GTE indicates that a grain
    in the child disk is zero‐filled but does not actually occupy space
    in storage.  A sparse extent with zeroed‐grain GTE has the following
    in its header:

     * SparseExtentHeader.version = 2
     * SparseExtentHeader.flags has bit 2 set

    Other than the new flag and the possibly zeroed‐grain GTE, version 2
    sparse extents are identical to version 1.  Also, a zeroed‐grain GTE
    has value 0x1 in the GT table.

[1] Virtual Disk Format 5.0, http://www.vmware.com/support/developer/vddk/vmdk_50_technote.pdf?src=vmdk
Signed-off-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
This commit is contained in:
Fam Zheng 2013-05-02 10:25:23 +08:00 committed by Stefan Hajnoczi
parent 65f7472577
commit 14ead646fe
1 changed files with 18 additions and 6 deletions
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24
block/vmdk.c
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@ -33,10 +33,13 @@
#define VMDK4_MAGIC (('K' << 24) | ('D' << 16) | ('M' << 8) | 'V')
#define VMDK4_COMPRESSION_DEFLATE 1
#define VMDK4_FLAG_RGD (1 << 1)
/* Zeroed-grain enable bit */
#define VMDK4_FLAG_ZERO_GRAIN (1 << 2)
#define VMDK4_FLAG_COMPRESS (1 << 16)
#define VMDK4_FLAG_MARKER (1 << 17)
#define VMDK4_GD_AT_END 0xffffffffffffffffULL
#define VMDK_GTE_ZEROED 0x1
/* VMDK internal error codes */
#define VMDK_OK 0
@ -81,6 +84,8 @@ typedef struct VmdkExtent {
bool flat;
bool compressed;
bool has_marker;
bool has_zero_grain;
int version;
int64_t sectors;
int64_t end_sector;
int64_t flat_start_offset;
@ -569,6 +574,8 @@ static int vmdk_open_vmdk4(BlockDriverState *bs,
extent->compressed =
le16_to_cpu(header.compressAlgorithm) == VMDK4_COMPRESSION_DEFLATE;
extent->has_marker = le32_to_cpu(header.flags) & VMDK4_FLAG_MARKER;
extent->version = le32_to_cpu(header.version);
extent->has_zero_grain = le32_to_cpu(header.flags) & VMDK4_FLAG_ZERO_GRAIN;
ret = vmdk_init_tables(bs, extent);
if (ret) {
/* free extent allocated by vmdk_add_extent */
@ -839,6 +846,7 @@ static int get_cluster_offset(BlockDriverState *bs,
unsigned int l1_index, l2_offset, l2_index;
int min_index, i, j;
uint32_t min_count, *l2_table, tmp = 0;
bool zeroed = false;
if (m_data) {
m_data->valid = 0;
@ -894,9 +902,13 @@ static int get_cluster_offset(BlockDriverState *bs,
l2_index = ((offset >> 9) / extent->cluster_sectors) % extent->l2_size;
*cluster_offset = le32_to_cpu(l2_table[l2_index]);
if (!*cluster_offset) {
if (extent->has_zero_grain && *cluster_offset == VMDK_GTE_ZEROED) {
zeroed = true;
}
if (!*cluster_offset || zeroed) {
if (!allocate) {
return VMDK_UNALLOC;
return zeroed ? VMDK_ZEROED : VMDK_UNALLOC;
}
/* Avoid the L2 tables update for the images that have snapshots. */
@ -967,8 +979,8 @@ static int coroutine_fn vmdk_co_is_allocated(BlockDriverState *bs,
ret = get_cluster_offset(bs, extent, NULL,
sector_num * 512, 0, &offset);
qemu_co_mutex_unlock(&s->lock);
/* get_cluster_offset returning 0 means success */
ret = !ret;
ret = (ret == VMDK_OK || ret == VMDK_ZEROED);
index_in_cluster = sector_num % extent->cluster_sectors;
n = extent->cluster_sectors - index_in_cluster;
@ -1111,9 +1123,9 @@ static int vmdk_read(BlockDriverState *bs, int64_t sector_num,
if (n > nb_sectors) {
n = nb_sectors;
}
if (ret) {
if (ret != VMDK_OK) {
/* if not allocated, try to read from parent image, if exist */
if (bs->backing_hd) {
if (bs->backing_hd && ret != VMDK_ZEROED) {
if (!vmdk_is_cid_valid(bs)) {
return -EINVAL;
}