Add a parameter that enables discard-after-copy. That is mostly useful
in "push backup with fleecing" scheme, when source is snapshot-access
format driver node, based on copy-before-write filter snapshot-access
API:
[guest] [snapshot-access] ~~ blockdev-backup ~~> [backup target]
||
| root | file
vv
[copy-before-write]
| |
| file| target
v v
[active disk] [temp.img]
In this case discard-after-copy does two things:
- discard data in temp.img to save disk space
- avoid further copy-before-write operation in discarded area
Note that we have to declare WRITE permission on source in
copy-before-write filter, for discard to work. Still we can't take it
unconditionally, as it will break normal backup from RO source. So, we
have to add a parameter and pass it thorough bdrv_open flags.
Signed-off-by: Vladimir Sementsov-Ogievskiy
Reviewed-by: Fiona Ebner
Tested-by: Fiona Ebner
---
block/backup.c | 5 +++--
block/block-copy.c | 9 +
block/copy-before-write.c | 15 +--
block/copy-before-write.h | 1 +
block/replication.c| 4 ++--
blockdev.c | 2 +-
include/block/block-common.h | 2 ++
include/block/block-copy.h | 1 +
include/block/block_int-global-state.h | 2 +-
qapi/block-core.json | 4
10 files changed, 37 insertions(+), 8 deletions(-)
diff --git a/block/backup.c b/block/backup.c
index ec29d6b810..3dd2e229d2 100644
--- a/block/backup.c
+++ b/block/backup.c
@@ -356,7 +356,7 @@ BlockJob *backup_job_create(const char *job_id,
BlockDriverState *bs,
BlockDriverState *target, int64_t speed,
MirrorSyncMode sync_mode, BdrvDirtyBitmap *sync_bitmap,
BitmapSyncMode bitmap_mode,
- bool compress,
+ bool compress, bool discard_source,
const char *filter_node_name,
BackupPerf *perf,
BlockdevOnError on_source_error,
@@ -457,7 +457,8 @@ BlockJob *backup_job_create(const char *job_id,
BlockDriverState *bs,
goto error;
}
-cbw = bdrv_cbw_append(bs, target, filter_node_name, , errp);
+cbw = bdrv_cbw_append(bs, target, filter_node_name, discard_source,
+ , errp);
if (!cbw) {
goto error;
}
diff --git a/block/block-copy.c b/block/block-copy.c
index 8fca2c3698..7e3b378528 100644
--- a/block/block-copy.c
+++ b/block/block-copy.c
@@ -137,6 +137,7 @@ typedef struct BlockCopyState {
CoMutex lock;
int64_t in_flight_bytes;
BlockCopyMethod method;
+bool discard_source;
BlockReqList reqs;
QLIST_HEAD(, BlockCopyCallState) calls;
/*
@@ -353,6 +354,7 @@ static int64_t
block_copy_calculate_cluster_size(BlockDriverState *target,
BlockCopyState *block_copy_state_new(BdrvChild *source, BdrvChild *target,
BlockDriverState *copy_bitmap_bs,
const BdrvDirtyBitmap *bitmap,
+ bool discard_source,
Error **errp)
{
ERRP_GUARD();
@@ -418,6 +420,7 @@ BlockCopyState *block_copy_state_new(BdrvChild *source,
BdrvChild *target,
cluster_size),
};
+s->discard_source = discard_source;
block_copy_set_copy_opts(s, false, false);
ratelimit_init(>rate_limit);
@@ -589,6 +592,12 @@ static coroutine_fn int block_copy_task_entry(AioTask
*task)
co_put_to_shres(s->mem, t->req.bytes);
block_copy_task_end(t, ret);
+if (s->discard_source && ret == 0) {
+int64_t nbytes =
+MIN(t->req.offset + t->req.bytes, s->len) - t->req.offset;
+bdrv_co_pdiscard(s->source, t->req.offset, nbytes);
+}
+
return ret;
}
diff --git a/block/copy-before-write.c b/block/copy-before-write.c
index ed2c228da7..cd65524e26 100644
--- a/block/copy-before-write.c
+++ b/block/copy-before-write.c
@@ -44,6 +44,7 @@ typedef struct BDRVCopyBeforeWriteState {
BdrvChild *target;
OnCbwError on_cbw_error;
uint32_t cbw_timeout_ns;
+bool discard_source;
/*
* @lock: protects access to @access_bitmap, @done_bitmap and
@@ -357,6 +358,8 @@ cbw_child_perm(BlockDriverState *bs, BdrvChild *c,
BdrvChildRole role,
uint64_t perm, uint64_t shared,
uint64_t *nperm, uint64_t *nshared)
{
+BDRVCopyBeforeWriteState *s = bs->opaque;
+
if (!(role & BDRV_CHILD_FILTERED)) {
/*
* Target child
@@ -381,6 +384,10 @@ cbw_child_perm(BlockDriverState *bs, BdrvChild *c,
BdrvChildRole role,
* start
*/
*nperm = *nperm | BLK_PERM_CONSISTENT_READ;
+if (s->discard_source) {
+*nperm = *nperm |
