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[Qemu-devel] [PULL 25/69] qcow2: refcount_order parameter for qcow2_crea
From: |
Stefan Hajnoczi |
Subject: |
[Qemu-devel] [PULL 25/69] qcow2: refcount_order parameter for qcow2_create2 |
Date: |
Fri, 27 Feb 2015 18:18:23 +0000 |
From: Max Reitz <address@hidden>
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 <address@hidden>
Reviewed-by: Eric Blake <address@hidden>
Signed-off-by: Kevin Wolf <address@hidden>
---
block/qcow2.c | 47 ++++++++++++++++++++++++++++++++++++-----------
1 file changed, 36 insertions(+), 11 deletions(-)
diff --git a/block/qcow2.c b/block/qcow2.c
index fd76e2c..04444bc 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);
@@ -1891,7 +1903,7 @@ 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)),
};
@@ -2010,6 +2022,8 @@ 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;
@@ -2064,8 +2078,19 @@ 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);
}
--
2.1.0
- [Qemu-devel] [PULL 15/69] qcow2: Add two new fields to BDRVQcowState, (continued)
- [Qemu-devel] [PULL 15/69] qcow2: Add two new fields to BDRVQcowState, Stefan Hajnoczi, 2015/02/27
- [Qemu-devel] [PULL 18/69] qcow2: Only return status from qcow2_get_refcount, Stefan Hajnoczi, 2015/02/27
- [Qemu-devel] [PULL 20/69] qcow2: Use 64 bits for refcount values, Stefan Hajnoczi, 2015/02/27
- [Qemu-devel] [PULL 17/69] qcow2: Do not return new value after refcount update, Stefan Hajnoczi, 2015/02/27
- [Qemu-devel] [PULL 19/69] qcow2: Use unsigned addend for update_refcount(), Stefan Hajnoczi, 2015/02/27
- [Qemu-devel] [PULL 21/69] qcow2: Helper for refcount array reallocation, Stefan Hajnoczi, 2015/02/27
- [Qemu-devel] [PULL 22/69] qcow2: Helper function for refcount modification, Stefan Hajnoczi, 2015/02/27
- [Qemu-devel] [PULL 24/69] qcow2: Open images with refcount order != 4, Stefan Hajnoczi, 2015/02/27
- [Qemu-devel] [PULL 26/69] qcow2: Use symbolic macros in qcow2_amend_options, Stefan Hajnoczi, 2015/02/27
- [Qemu-devel] [PULL 23/69] qcow2: More helpers for refcount modification, Stefan Hajnoczi, 2015/02/27
- [Qemu-devel] [PULL 25/69] qcow2: refcount_order parameter for qcow2_create2,
Stefan Hajnoczi <=
- [Qemu-devel] [PULL 28/69] qcow2: Allow creation with refcount order != 4, Stefan Hajnoczi, 2015/02/27
- [Qemu-devel] [PULL 29/69] iotests: Add test for different refcount widths, Stefan Hajnoczi, 2015/02/27
- [Qemu-devel] [PULL 27/69] iotests: Prepare for refcount_bits option, Stefan Hajnoczi, 2015/02/27
- [Qemu-devel] [PULL 31/69] block: add bdrv functions for geometry and blocksize, Stefan Hajnoczi, 2015/02/27
- [Qemu-devel] [PULL 30/69] blkdebug: fix "once" rule, Stefan Hajnoczi, 2015/02/27
- [Qemu-devel] [PULL 34/69] block-backend: Add wrappers for blocksizes and geometry probing, Stefan Hajnoczi, 2015/02/27
- [Qemu-devel] [PULL 33/69] block: Add driver methods to probe blocksizes and geometry, Stefan Hajnoczi, 2015/02/27
- [Qemu-devel] [PULL 39/69] ide: do not use BMDMA in restart callback, Stefan Hajnoczi, 2015/02/27
- [Qemu-devel] [PULL 36/69] ide: start extracting ide_restart_dma out of bmdma_restart_dma, Stefan Hajnoczi, 2015/02/27
- [Qemu-devel] [PULL 37/69] ide: prepare to move restart to common code, Stefan Hajnoczi, 2015/02/27