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[Qemu-devel] [PATCH v6 11/24] qcow2: refcount_order parameter for qcow2_
From: |
Max Reitz |
Subject: |
[Qemu-devel] [PATCH v6 11/24] qcow2: refcount_order parameter for qcow2_create2 |
Date: |
Tue, 10 Feb 2015 15:28:53 -0500 |
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>
Reviewed-by: Stefan Hajnoczi <address@hidden>
---
block/qcow2.c | 46 +++++++++++++++++++++++++++++++++++-----------
1 file changed, 35 insertions(+), 11 deletions(-)
diff --git a/block/qcow2.c b/block/qcow2.c
index e563a30..b7c023e 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 +2022,7 @@ static int qcow2_create(const char *filename, QemuOpts
*opts, Error **errp)
size_t cluster_size = DEFAULT_CLUSTER_SIZE;
PreallocMode prealloc;
int version = 3;
+ int refcount_bits = 16, refcount_order;
Error *local_err = NULL;
int ret;
@@ -2064,8 +2077,19 @@ 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] [PATCH v6 08/24] qcow2: Helper function for refcount modification, (continued)
- [Qemu-devel] [PATCH v6 08/24] qcow2: Helper function for refcount modification, Max Reitz, 2015/02/10
- [Qemu-devel] [PATCH v6 12/24] qcow2: Use symbolic macros in qcow2_amend_options, Max Reitz, 2015/02/10
- [Qemu-devel] [PATCH v6 07/24] qcow2: Helper for refcount array reallocation, Max Reitz, 2015/02/10
- [Qemu-devel] [PATCH v6 09/24] qcow2: More helpers for refcount modification, Max Reitz, 2015/02/10
- [Qemu-devel] [PATCH v6 13/24] iotests: Prepare for refcount_bits option, Max Reitz, 2015/02/10
- [Qemu-devel] [PATCH v6 15/24] progress: Allow regressing progress, Max Reitz, 2015/02/10
- [Qemu-devel] [PATCH v6 11/24] qcow2: refcount_order parameter for qcow2_create2,
Max Reitz <=
- [Qemu-devel] [PATCH v6 20/24] qcow2: Use intermediate helper CB for amend, Max Reitz, 2015/02/10
- [Qemu-devel] [PATCH v6 16/24] block: Add opaque value to the amend CB, Max Reitz, 2015/02/10
- [Qemu-devel] [PATCH v6 14/24] qcow2: Allow creation with refcount order != 4, Max Reitz, 2015/02/10
- [Qemu-devel] [PATCH v6 17/24] qcow2: Use error_report() in qcow2_amend_options(), Max Reitz, 2015/02/10
- [Qemu-devel] [PATCH v6 18/24] qcow2: Use abort() instead of assert(false), Max Reitz, 2015/02/10
- [Qemu-devel] [PATCH v6 23/24] qcow2: Point to amend function in check, Max Reitz, 2015/02/10
- [Qemu-devel] [PATCH v6 19/24] qcow2: Split upgrade/downgrade paths for amend, Max Reitz, 2015/02/10
- [Qemu-devel] [PATCH v6 22/24] qcow2: Invoke refcount order amendment function, Max Reitz, 2015/02/10