*/
#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)
/* 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
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)
/* 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);
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;
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;
/* 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;