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authorMax Reitz <mreitz@redhat.com>2015-02-18 17:40:46 -0500
committerKevin Wolf <kwolf@redhat.com>2015-03-10 14:02:21 +0100
commitbd4b167f84840865b788e9f236585f77a77b10fc (patch)
treeead7cfe670020bceae762214285ef4a636990d5c
parentb72faf9f78377e38342f78ffacdfa0726f5e7511 (diff)
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qcow2: refcount_order parameter for qcow2_create2
Add a refcount_order parameter to qcow2_create2(), use that value for the image header and for calculating the size required for preallocation. For now, always pass 4. This addition requires changes to the calculation of the file size for the "full" and "falloc" preallocation modes. That in turn is a nice opportunity to add a comment about that calculation not necessarily being exact (and that being intentional). Signed-off-by: Max Reitz <mreitz@redhat.com> Reviewed-by: Eric Blake <eblake@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
-rw-r--r--block/qcow2.c47
1 files changed, 36 insertions, 11 deletions
diff --git a/block/qcow2.c b/block/qcow2.c
index 52731ab..7a35f97 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -1783,7 +1783,7 @@ static int preallocate(BlockDriverState *bs)
static int qcow2_create2(const char *filename, int64_t total_size,
const char *backing_file, const char *backing_format,
int flags, size_t cluster_size, PreallocMode prealloc,
- QemuOpts *opts, int version,
+ QemuOpts *opts, int version, int refcount_order,
Error **errp)
{
/* Calculate cluster_bits */
@@ -1816,9 +1816,21 @@ static int qcow2_create2(const char *filename, int64_t total_size,
int ret;
if (prealloc == PREALLOC_MODE_FULL || prealloc == PREALLOC_MODE_FALLOC) {
+ /* Note: The following calculation does not need to be exact; if it is a
+ * bit off, either some bytes will be "leaked" (which is fine) or we
+ * will need to increase the file size by some bytes (which is fine,
+ * too, as long as the bulk is allocated here). Therefore, using
+ * floating point arithmetic is fine. */
int64_t meta_size = 0;
uint64_t nreftablee, nrefblocke, nl1e, nl2e;
int64_t aligned_total_size = align_offset(total_size, cluster_size);
+ int refblock_bits, refblock_size;
+ /* refcount entry size in bytes */
+ double rces = (1 << refcount_order) / 8.;
+
+ /* see qcow2_open() */
+ refblock_bits = cluster_bits - (refcount_order - 3);
+ refblock_size = 1 << refblock_bits;
/* header: 1 cluster */
meta_size += cluster_size;
@@ -1843,20 +1855,20 @@ static int qcow2_create2(const char *filename, int64_t total_size,
* c = cluster size
* y1 = number of refcount blocks entries
* y2 = meta size including everything
+ * rces = refcount entry size in bytes
* then,
* y1 = (y2 + a)/c
- * y2 = y1 * sizeof(u16) + y1 * sizeof(u16) * sizeof(u64) / c + m
+ * y2 = y1 * rces + y1 * rces * sizeof(u64) / c + m
* we can get y1:
- * y1 = (a + m) / (c - sizeof(u16) - sizeof(u16) * sizeof(u64) / c)
+ * y1 = (a + m) / (c - rces - rces * 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);
+ nrefblocke = (aligned_total_size + meta_size + cluster_size)
+ / (cluster_size - rces - rces * sizeof(uint64_t)
+ / cluster_size);
+ meta_size += DIV_ROUND_UP(nrefblocke, refblock_size) * cluster_size;
/* total size of refcount tables */
- nreftablee = nrefblocke * sizeof(uint16_t) / cluster_size;
+ nreftablee = nrefblocke / refblock_size;
nreftablee = align_offset(nreftablee, cluster_size / sizeof(uint64_t));
meta_size += nreftablee * sizeof(uint64_t);
@@ -1892,7 +1904,7 @@ static int qcow2_create2(const char *filename, int64_t total_size,
.l1_size = cpu_to_be32(0),
.refcount_table_offset = cpu_to_be64(cluster_size),
.refcount_table_clusters = cpu_to_be32(1),
- .refcount_order = cpu_to_be32(4),
+ .refcount_order = cpu_to_be32(refcount_order),
.header_length = cpu_to_be32(sizeof(*header)),
};
@@ -2011,6 +2023,8 @@ static int qcow2_create(const char *filename, QemuOpts *opts, Error **errp)
size_t cluster_size = DEFAULT_CLUSTER_SIZE;
PreallocMode prealloc;
int version = 3;
+ uint64_t refcount_bits = 16;
+ int refcount_order;
Error *local_err = NULL;
int ret;
@@ -2065,8 +2079,19 @@ static int qcow2_create(const char *filename, QemuOpts *opts, Error **errp)
goto finish;
}
+ if (version < 3 && refcount_bits != 16) {
+ error_setg(errp, "Different refcount widths than 16 bits require "
+ "compatibility level 1.1 or above (use compat=1.1 or "
+ "greater)");
+ ret = -EINVAL;
+ goto finish;
+ }
+
+ refcount_order = ffs(refcount_bits) - 1;
+
ret = qcow2_create2(filename, size, backing_file, backing_fmt, flags,
- cluster_size, prealloc, opts, version, &local_err);
+ cluster_size, prealloc, opts, version, refcount_order,
+ &local_err);
if (local_err) {
error_propagate(errp, local_err);
}