[pve-devel] [PATCH qemu v3 04/22] qapi: blockdev-backup: add discard-source parameter
Fiona Ebner
f.ebner at proxmox.com
Thu Apr 11 11:29:25 CEST 2024
From: Vladimir Sementsov-Ogievskiy <vsementsov at yandex-team.ru>
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
v v
[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 <vsementsov at yandex-team.ru>
Signed-off-by: Fiona Ebner <f.ebner at proxmox.com>
---
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 af87fa6aa9..3dc955f625 100644
--- a/block/backup.c
+++ b/block/backup.c
@@ -332,7 +332,7 @@ 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,
@@ -429,7 +429,8 @@ BlockJob *backup_job_create(const char *job_id, BlockDriverState *bs,
goto error;
}
- cbw = bdrv_cbw_append(bs, target, filter_node_name, &bcs, errp);
+ cbw = bdrv_cbw_append(bs, target, filter_node_name, discard_source,
+ &bcs, errp);
if (!cbw) {
goto error;
}
diff --git a/block/block-copy.c b/block/block-copy.c
index b61685f1a2..3c61e52bae 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;
/*
@@ -348,6 +349,7 @@ 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();
@@ -409,6 +411,7 @@ 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(&s->rate_limit);
@@ -580,6 +583,12 @@ 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 d3b95bd600..3503702d71 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 @@ static void cbw_child_perm(BlockDriverState *bs, BdrvChild *c,
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 @@ static void cbw_child_perm(BlockDriverState *bs, BdrvChild *c,
* start
*/
*nperm = *nperm | BLK_PERM_CONSISTENT_READ;
+ if (s->discard_source) {
+ *nperm = *nperm | BLK_PERM_WRITE;
+ }
+
*nshared &= ~(BLK_PERM_WRITE | BLK_PERM_RESIZE);
}
}
@@ -470,7 +477,9 @@ static int cbw_open(BlockDriverState *bs, QDict *options, int flags,
((BDRV_REQ_FUA | BDRV_REQ_MAY_UNMAP | BDRV_REQ_NO_FALLBACK) &
bs->file->bs->supported_zero_flags);
- s->bcs = block_copy_state_new(bs->file, s->target, bs, bitmap, errp);
+ s->discard_source = flags & BDRV_O_CBW_DISCARD_SOURCE;
+ s->bcs = block_copy_state_new(bs->file, s->target, bs, bitmap,
+ flags & BDRV_O_CBW_DISCARD_SOURCE, errp);
if (!s->bcs) {
error_prepend(errp, "Cannot create block-copy-state: ");
ret = -EINVAL;
@@ -544,12 +553,14 @@ BlockDriver bdrv_cbw_filter = {
BlockDriverState *bdrv_cbw_append(BlockDriverState *source,
BlockDriverState *target,
const char *filter_node_name,
+ bool discard_source,
BlockCopyState **bcs,
Error **errp)
{
BDRVCopyBeforeWriteState *state;
BlockDriverState *top;
QDict *opts;
+ int flags = BDRV_O_RDWR | (discard_source ? BDRV_O_CBW_DISCARD_SOURCE : 0);
assert(source->total_sectors == target->total_sectors);
GLOBAL_STATE_CODE();
@@ -562,7 +573,7 @@ BlockDriverState *bdrv_cbw_append(BlockDriverState *source,
qdict_put_str(opts, "file", bdrv_get_node_name(source));
qdict_put_str(opts, "target", bdrv_get_node_name(target));
- top = bdrv_insert_node(source, opts, BDRV_O_RDWR, errp);
+ top = bdrv_insert_node(source, opts, flags, errp);
if (!top) {
return NULL;
}
diff --git a/block/copy-before-write.h b/block/copy-before-write.h
index 6e72bb25e9..01af0cd3c4 100644
--- a/block/copy-before-write.h
+++ b/block/copy-before-write.h
@@ -39,6 +39,7 @@
BlockDriverState *bdrv_cbw_append(BlockDriverState *source,
BlockDriverState *target,
const char *filter_node_name,
+ bool discard_source,
BlockCopyState **bcs,
Error **errp);
void bdrv_cbw_drop(BlockDriverState *bs);
diff --git a/block/replication.c b/block/replication.c
index ea4bf1aa80..39ad78cf98 100644
--- a/block/replication.c
+++ b/block/replication.c
@@ -579,8 +579,8 @@ static void replication_start(ReplicationState *rs, ReplicationMode mode,
s->backup_job = backup_job_create(
NULL, s->secondary_disk->bs, s->hidden_disk->bs,
- 0, MIRROR_SYNC_MODE_NONE, NULL, 0, false, NULL,
- &perf,
+ 0, MIRROR_SYNC_MODE_NONE, NULL, 0, false, false,
+ NULL, &perf,
BLOCKDEV_ON_ERROR_REPORT,
BLOCKDEV_ON_ERROR_REPORT, JOB_INTERNAL,
backup_job_completed, bs, NULL, &local_err);
diff --git a/blockdev.c b/blockdev.c
index 7793143d76..ce3fef924c 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -2802,7 +2802,7 @@ static BlockJob *do_backup_common(BackupCommon *backup,
job = backup_job_create(backup->job_id, bs, target_bs, backup->speed,
backup->sync, bmap, backup->bitmap_mode,
- backup->compress,
+ backup->compress, backup->discard_source,
backup->filter_node_name,
&perf,
backup->on_source_error,
diff --git a/include/block/block-common.h b/include/block/block-common.h
index e15395f2cb..913a8b259c 100644
--- a/include/block/block-common.h
+++ b/include/block/block-common.h
@@ -234,6 +234,8 @@ typedef enum {
read-write fails */
#define BDRV_O_IO_URING 0x40000 /* use io_uring instead of the thread pool */
+#define BDRV_O_CBW_DISCARD_SOURCE 0x80000 /* for copy-before-write filter */
+
#define BDRV_O_CACHE_MASK (BDRV_O_NOCACHE | BDRV_O_NO_FLUSH)
diff --git a/include/block/block-copy.h b/include/block/block-copy.h
index 8b41643bfa..bdc703bacd 100644
--- a/include/block/block-copy.h
+++ b/include/block/block-copy.h
@@ -27,6 +27,7 @@ typedef struct BlockCopyCallState BlockCopyCallState;
BlockCopyState *block_copy_state_new(BdrvChild *source, BdrvChild *target,
BlockDriverState *copy_bitmap_bs,
const BdrvDirtyBitmap *bitmap,
+ bool discard_source,
Error **errp);
/* Function should be called prior any actual copy request */
diff --git a/include/block/block_int-global-state.h b/include/block/block_int-global-state.h
index 32f0f9858a..546f2b5532 100644
--- a/include/block/block_int-global-state.h
+++ b/include/block/block_int-global-state.h
@@ -189,7 +189,7 @@ BlockJob *backup_job_create(const char *job_id, BlockDriverState *bs,
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,
diff --git a/qapi/block-core.json b/qapi/block-core.json
index 09de550c95..4297e5beda 100644
--- a/qapi/block-core.json
+++ b/qapi/block-core.json
@@ -1816,6 +1816,9 @@
# node specified by @drive. If this option is not given, a node
# name is autogenerated. (Since: 4.2)
#
+# @discard-source: Discard blocks on source which are already copied
+# to the target. (Since 9.0)
+#
# @x-perf: Performance options. (Since 6.0)
#
# Features:
@@ -1837,6 +1840,7 @@
'*on-target-error': 'BlockdevOnError',
'*auto-finalize': 'bool', '*auto-dismiss': 'bool',
'*filter-node-name': 'str',
+ '*discard-source': 'bool',
'*x-perf': { 'type': 'BackupPerf',
'features': [ 'unstable' ] } } }
--
2.39.2
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