--- /dev/null
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
+Date: Thu, 11 Apr 2024 11:29:25 +0200
+Subject: [PATCH] qapi: blockdev-backup: add discard-source parameter
+
+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@yandex-team.ru>
+Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>
+Signed-off-by: Thomas Lamprecht <t.lamprecht@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' ] } } }
+
projects / pve-qemu.git / blobdiff