OpenE2K/qemu-e2k
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Teach block/vdi about "discarded" (no longer allocated) blocks

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An entry in the VDI block map will hold an offset to the actual block if
the block is allocated, or one of two specially-interpreted values if
not allocated. Using VirtualBox terminology, value VDI_IMAGE_BLOCK_FREE
(0xffffffff) represents a never-allocated block (semantically arbitrary
content).  VDI_IMAGE_BLOCK_ZERO (0xfffffffe) represents a "discarded"
block (semantically zero-filled).  block/vdi knows only about
VDI_IMAGE_BLOCK_FREE.  Teach it about VDI_IMAGE_BLOCK_ZERO.

Signed-off-by: Eric Sunshine <sunshine@sunshineco.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Eric Sunshine 2011-10-26 15:51:18 -04:00 committed by Kevin Wolf
parent 0f5314a2c8
commit c794b4e0fd
1 changed files with 14 additions and 9 deletions
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23
block/vdi.c
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@ -114,8 +114,13 @@ void uuid_unparse(const uuid_t uu, char *out);
*/
#define VDI_TEXT "<<< QEMU VM Virtual Disk Image >>>\n"
/* Unallocated blocks use this index (no need to convert endianness). */
#define VDI_UNALLOCATED UINT32_MAX
/* A never-allocated block; semantically arbitrary content. */
#define VDI_UNALLOCATED 0xffffffffU
/* A discarded (no longer allocated) block; semantically zero-filled. */
#define VDI_DISCARDED 0xfffffffeU
#define VDI_IS_ALLOCATED(X) ((X) < VDI_DISCARDED)
#if !defined(CONFIG_UUID)
void uuid_generate(uuid_t out)
@ -307,10 +312,10 @@ static int vdi_check(BlockDriverState *bs, BdrvCheckResult *res)
/* Check block map and value of blocks_allocated. */
for (block = 0; block < s->header.blocks_in_image; block++) {
uint32_t bmap_entry = le32_to_cpu(s->bmap[block]);
if (bmap_entry != VDI_UNALLOCATED) {
if (VDI_IS_ALLOCATED(bmap_entry)) {
if (bmap_entry < s->header.blocks_in_image) {
blocks_allocated++;
if (bmap[bmap_entry] == VDI_UNALLOCATED) {
if (!VDI_IS_ALLOCATED(bmap[bmap_entry])) {
bmap[bmap_entry] = bmap_entry;
} else {
fprintf(stderr, "ERROR: block index %" PRIu32
@ -472,7 +477,7 @@ static int vdi_is_allocated(BlockDriverState *bs, int64_t sector_num,
n_sectors = nb_sectors;
}
*pnum = n_sectors;
return bmap_entry != VDI_UNALLOCATED;
return VDI_IS_ALLOCATED(bmap_entry);
}
static void vdi_aio_cancel(BlockDriverAIOCB *blockacb)
@ -603,7 +608,7 @@ static void vdi_aio_read_cb(void *opaque, int ret)
/* prepare next AIO request */
acb->n_sectors = n_sectors;
bmap_entry = le32_to_cpu(s->bmap[block_index]);
if (bmap_entry == VDI_UNALLOCATED) {
if (!VDI_IS_ALLOCATED(bmap_entry)) {
/* Block not allocated, return zeros, no need to wait. */
memset(acb->buf, 0, n_sectors * SECTOR_SIZE);
ret = vdi_schedule_bh(vdi_aio_rw_bh, acb);
@ -685,7 +690,7 @@ static void vdi_aio_write_cb(void *opaque, int ret)
if (acb->header_modified) {
VdiHeader *header = acb->block_buffer;
logout("now writing modified header\n");
assert(acb->bmap_first != VDI_UNALLOCATED);
assert(VDI_IS_ALLOCATED(acb->bmap_first));
*header = s->header;
vdi_header_to_le(header);
acb->header_modified = 0;
@ -699,7 +704,7 @@ static void vdi_aio_write_cb(void *opaque, int ret)
goto done;
}
return;
} else if (acb->bmap_first != VDI_UNALLOCATED) {
} else if (VDI_IS_ALLOCATED(acb->bmap_first)) {
/* One or more new blocks were allocated. */
uint64_t offset;
uint32_t bmap_first;
@ -749,7 +754,7 @@ static void vdi_aio_write_cb(void *opaque, int ret)
/* prepare next AIO request */
acb->n_sectors = n_sectors;
bmap_entry = le32_to_cpu(s->bmap[block_index]);
if (bmap_entry == VDI_UNALLOCATED) {
if (!VDI_IS_ALLOCATED(bmap_entry)) {
/* Allocate new block and write to it. */
uint64_t offset;
uint8_t *block;