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qcow2: Options to enable discard for freed clusters

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Deleted snapshots are discarded in the image file by default, discard
requests take their default from the -drive discard=... option and other
places that free clusters must always be enabled explicitly.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
This commit is contained in:
Kevin Wolf 2013-06-19 13:44:19 +02:00 committed by Stefan Hajnoczi
parent 6cfcb9b8b9
commit 67af674e47
3 changed files with 36 additions and 0 deletions
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5
block/qcow2-refcount.c
View File

@ -488,6 +488,11 @@ static int QEMU_WARN_UNUSED_RESULT update_refcount(BlockDriverState *bs,
s->free_cluster_index = cluster_index;
}
refcount_block[block_index] = cpu_to_be16(refcount);
if (refcount == 0 && s->discard_passthrough[type]) {
/* Try discarding, ignore errors */
/* FIXME Doing this cluster by cluster will be painfully slow */
bdrv_discard(bs->file, cluster_offset, 1);
}
}
ret = 0;

26
block/qcow2.c
View File

@ -295,6 +295,22 @@ static QemuOptsList qcow2_runtime_opts = {
.type = QEMU_OPT_BOOL,
.help = "Postpone refcount updates",
},
{
.name = QCOW2_OPT_DISCARD_REQUEST,
.type = QEMU_OPT_BOOL,
.help = "Pass guest discard requests to the layer below",
},
{
.name = QCOW2_OPT_DISCARD_SNAPSHOT,
.type = QEMU_OPT_BOOL,
.help = "Generate discard requests when snapshot related space "
"is freed",
},
{
.name = QCOW2_OPT_DISCARD_OTHER,
.type = QEMU_OPT_BOOL,
.help = "Generate discard requests when other clusters are freed",
},
{ /* end of list */ }
},
};
@ -532,6 +548,16 @@ static int qcow2_open(BlockDriverState *bs, QDict *options, int flags)
s->use_lazy_refcounts = qemu_opt_get_bool(opts, QCOW2_OPT_LAZY_REFCOUNTS,
(s->compatible_features & QCOW2_COMPAT_LAZY_REFCOUNTS));
s->discard_passthrough[QCOW2_DISCARD_NEVER] = false;
s->discard_passthrough[QCOW2_DISCARD_ALWAYS] = true;
s->discard_passthrough[QCOW2_DISCARD_REQUEST] =
qemu_opt_get_bool(opts, QCOW2_OPT_DISCARD_REQUEST,
flags & BDRV_O_UNMAP);
s->discard_passthrough[QCOW2_DISCARD_SNAPSHOT] =
qemu_opt_get_bool(opts, QCOW2_OPT_DISCARD_SNAPSHOT, true);
s->discard_passthrough[QCOW2_DISCARD_OTHER] =
qemu_opt_get_bool(opts, QCOW2_OPT_DISCARD_OTHER, false);
qemu_opts_del(opts);
if (s->use_lazy_refcounts && s->qcow_version < 3) {

5
block/qcow2.h
View File

@ -60,6 +60,9 @@
#define QCOW2_OPT_LAZY_REFCOUNTS "lazy_refcounts"
#define QCOW2_OPT_DISCARD_REQUEST "pass_discard_request"
#define QCOW2_OPT_DISCARD_SNAPSHOT "pass_discard_snapshot"
#define QCOW2_OPT_DISCARD_OTHER "pass_discard_other"
typedef struct QCowHeader {
uint32_t magic;
@ -187,6 +190,8 @@ typedef struct BDRVQcowState {
int qcow_version;
bool use_lazy_refcounts;
bool discard_passthrough[QCOW2_DISCARD_MAX];
uint64_t incompatible_features;
uint64_t compatible_features;
uint64_t autoclear_features;