qcow2: Add falloc and full preallocation option
preallocation=falloc allocates disk space by posix_fallocate(),
preallocation=full allocates disk space by writing zeros to disk.
Both modes imply preallocation=metadata.
Signed-off-by: Hu Tao <hutao@cn.fujitsu.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
diff --git a/block/qcow2.c b/block/qcow2.c
index 2d68b51..0daf25c 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -1772,6 +1772,56 @@
Error *local_err = NULL;
int ret;
+ if (prealloc == PREALLOC_MODE_FULL || prealloc == PREALLOC_MODE_FALLOC) {
+ int64_t meta_size = 0;
+ uint64_t nreftablee, nrefblocke, nl1e, nl2e;
+ int64_t aligned_total_size = align_offset(total_size, cluster_size);
+
+ /* header: 1 cluster */
+ meta_size += cluster_size;
+
+ /* total size of L2 tables */
+ nl2e = aligned_total_size / cluster_size;
+ nl2e = align_offset(nl2e, cluster_size / sizeof(uint64_t));
+ meta_size += nl2e * sizeof(uint64_t);
+
+ /* total size of L1 tables */
+ nl1e = nl2e * sizeof(uint64_t) / cluster_size;
+ nl1e = align_offset(nl1e, cluster_size / sizeof(uint64_t));
+ meta_size += nl1e * sizeof(uint64_t);
+
+ /* total size of refcount blocks
+ *
+ * note: every host cluster is reference-counted, including metadata
+ * (even refcount blocks are recursively included).
+ * Let:
+ * a = total_size (this is the guest disk size)
+ * m = meta size not including refcount blocks and refcount tables
+ * c = cluster size
+ * y1 = number of refcount blocks entries
+ * y2 = meta size including everything
+ * then,
+ * y1 = (y2 + a)/c
+ * y2 = y1 * sizeof(u16) + y1 * sizeof(u16) * sizeof(u64) / c + m
+ * we can get y1:
+ * y1 = (a + m) / (c - sizeof(u16) - sizeof(u16) * sizeof(u64) / c)
+ */
+ nrefblocke = (aligned_total_size + meta_size + cluster_size) /
+ (cluster_size - sizeof(uint16_t) -
+ 1.0 * sizeof(uint16_t) * sizeof(uint64_t) / cluster_size);
+ nrefblocke = align_offset(nrefblocke, cluster_size / sizeof(uint16_t));
+ meta_size += nrefblocke * sizeof(uint16_t);
+
+ /* total size of refcount tables */
+ nreftablee = nrefblocke * sizeof(uint16_t) / cluster_size;
+ nreftablee = align_offset(nreftablee, cluster_size / sizeof(uint64_t));
+ meta_size += nreftablee * sizeof(uint64_t);
+
+ qemu_opt_set_number(opts, BLOCK_OPT_SIZE,
+ aligned_total_size + meta_size);
+ qemu_opt_set(opts, BLOCK_OPT_PREALLOC, PreallocMode_lookup[prealloc]);
+ }
+
ret = bdrv_create_file(filename, opts, &local_err);
if (ret < 0) {
error_propagate(errp, local_err);
@@ -1877,7 +1927,7 @@
}
/* And if we're supposed to preallocate metadata, do that now */
- if (prealloc == PREALLOC_MODE_METADATA) {
+ if (prealloc != PREALLOC_MODE_OFF) {
BDRVQcowState *s = bs->opaque;
qemu_co_mutex_lock(&s->lock);
ret = preallocate(bs);
@@ -1958,14 +2008,6 @@
flags |= BLOCK_FLAG_LAZY_REFCOUNTS;
}
- if (prealloc != PREALLOC_MODE_OFF &&
- prealloc != PREALLOC_MODE_METADATA) {
- ret = -EINVAL;
- error_setg(errp, "Unsupported preallocate mode: %s",
- PreallocMode_lookup[prealloc]);
- goto finish;
- }
-
if (backing_file && prealloc != PREALLOC_MODE_OFF) {
error_setg(errp, "Backing file and preallocation cannot be used at "
"the same time");
@@ -2526,7 +2568,8 @@
{
.name = BLOCK_OPT_PREALLOC,
.type = QEMU_OPT_STRING,
- .help = "Preallocation mode (allowed values: off, metadata)"
+ .help = "Preallocation mode (allowed values: off, metadata, "
+ "falloc, full)"
},
{
.name = BLOCK_OPT_LAZY_REFCOUNTS,
