| Message ID | 20240117160737.1057513-4-vsementsov@yandex-team.ru |
|---|---|
| State | New |
| Headers | show |
| Series | backup: discard-source parameter | expand |
Am 17.01.24 um 17:07 schrieb Vladimir Sementsov-Ogievskiy: > 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. > > Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru> Unfortunately, setting BLK_PERM_WRITE unconditionally breaks blockdev-backup for a read-only node (even when not using discard-source): > #!/bin/bash > ./qemu-img create /tmp/disk.raw -f raw 1G > ./qemu-img create /tmp/backup.raw -f raw 1G > ./qemu-system-x86_64 --qmp stdio \ > --blockdev raw,node-name=node0,file.driver=file,file.filename=/tmp/disk.raw,read-only=true \ > --blockdev raw,node-name=node1,file.driver=file,file.filename=/tmp/backup.raw \ > <<EOF > {"execute": "qmp_capabilities"} > {"execute": "blockdev-backup", "arguments": { "device": "node0", "target": "node1", "sync": "full", "job-id": "backup0" } } > EOF The above works before applying this patch, but leads to an error afterwards: > {"error": {"class": "GenericError", "desc": "Block node is read-only"}} Best Regards, Fiona
Am 17.01.24 um 17:07 schrieb Vladimir Sementsov-Ogievskiy: > 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. > > Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru> Ran into another issue when the cluster_size of the fleecing image is larger than for the backup target, e.g. > #!/bin/bash > rm /tmp/fleecing.qcow2 > ./qemu-img create /tmp/disk.qcow2 -f qcow2 1G > ./qemu-img create /tmp/fleecing.qcow2 -o cluster_size=2M -f qcow2 1G > ./qemu-img create /tmp/backup.qcow2 -f qcow2 1G > ./qemu-system-x86_64 --qmp stdio \ > --blockdev qcow2,node-name=node0,file.driver=file,file.filename=/tmp/disk.qcow2 \ > --blockdev qcow2,node-name=node1,file.driver=file,file.filename=/tmp/fleecing.qcow2,discard=unmap \ > --blockdev qcow2,node-name=node2,file.driver=file,file.filename=/tmp/backup.qcow2 \ > <<EOF > {"execute": "qmp_capabilities"} > {"execute": "blockdev-add", "arguments": { "driver": "copy-before-write", "file": "node0", "target": "node1", "node-name": "node3" } } > {"execute": "blockdev-add", "arguments": { "driver": "snapshot-access", "file": "node3", "discard": "unmap", "node-name": "snap0" } } > {"execute": "blockdev-backup", "arguments": { "device": "snap0", "target": "node2", "sync": "full", "job-id": "backup0", "discard-source": true } } > EOF will fail with > qemu-system-x86_64: ../util/hbitmap.c:570: hbitmap_reset: Assertion `QEMU_IS_ALIGNED(count, gran) || (start + count == hb->orig_size)' failed. Backtrace shows the assert happens while discarding, when resetting the BDRVCopyBeforeWriteState access_bitmap > #6 0x0000555556142a2a in hbitmap_reset (hb=0x555557e01b80, start=0, count=1048576) at ../util/hbitmap.c:570 > #7 0x0000555555f80764 in bdrv_reset_dirty_bitmap_locked (bitmap=0x55555850a660, offset=0, bytes=1048576) at ../block/dirty-bitmap.c:563 > #8 0x0000555555f807ab in bdrv_reset_dirty_bitmap (bitmap=0x55555850a660, offset=0, bytes=1048576) at ../block/dirty-bitmap.c:570 > #9 0x0000555555f7bb16 in cbw_co_pdiscard_snapshot (bs=0x5555581a7f60, offset=0, bytes=1048576) at ../block/copy-before-write.c:330 > #10 0x0000555555f8d00a in bdrv_co_pdiscard_snapshot (bs=0x5555581a7f60, offset=0, bytes=1048576) at ../block/io.c:3734 > #11 0x0000555555fd2380 in snapshot_access_co_pdiscard (bs=0x5555582b4f60, offset=0, bytes=1048576) at ../block/snapshot-access.c:55 > #12 0x0000555555f8b65d in bdrv_co_pdiscard (child=0x5555584fe790, offset=0, bytes=1048576) at ../block/io.c:3144 > #13 0x0000555555f78650 in block_copy_task_entry (task=0x555557f588f0) at ../block/block-copy.c:597 My guess for the cause is that in block_copy_calculate_cluster_size() we only look at the target. But now that we need to discard the source, we'll also need to consider that for the calculation? Best Regards, Fiona
Am 24.01.24 um 16:03 schrieb Fiona Ebner: > Am 17.01.24 um 17:07 schrieb Vladimir Sementsov-Ogievskiy: >> 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. >> >> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru> > > Ran into another issue when the cluster_size of the fleecing image is > larger than for the backup target, e.g. > >> #!/bin/bash >> rm /tmp/fleecing.qcow2 >> ./qemu-img create /tmp/disk.qcow2 -f qcow2 1G >> ./qemu-img create /tmp/fleecing.qcow2 -o cluster_size=2M -f qcow2 1G >> ./qemu-img create /tmp/backup.qcow2 -f qcow2 1G >> ./qemu-system-x86_64 --qmp stdio \ >> --blockdev qcow2,node-name=node0,file.driver=file,file.filename=/tmp/disk.qcow2 \ >> --blockdev qcow2,node-name=node1,file.driver=file,file.filename=/tmp/fleecing.qcow2,discard=unmap \ >> --blockdev qcow2,node-name=node2,file.driver=file,file.filename=/tmp/backup.qcow2 \ >> <<EOF >> {"execute": "qmp_capabilities"} >> {"execute": "blockdev-add", "arguments": { "driver": "copy-before-write", "file": "node0", "target": "node1", "node-name": "node3" } } >> {"execute": "blockdev-add", "arguments": { "driver": "snapshot-access", "file": "node3", "discard": "unmap", "node-name": "snap0" } } >> {"execute": "blockdev-backup", "arguments": { "device": "snap0", "target": "node2", "sync": "full", "job-id": "backup0", "discard-source": true } } >> EOF > > will fail with > >> qemu-system-x86_64: ../util/hbitmap.c:570: hbitmap_reset: Assertion `QEMU_IS_ALIGNED(count, gran) || (start + count == hb->orig_size)' failed. > > Backtrace shows the assert happens while discarding, when resetting the > BDRVCopyBeforeWriteState access_bitmap > > #6 0x0000555556142a2a in hbitmap_reset (hb=0x555557e01b80, start=0, > count=1048576) at ../util/hbitmap.c:570 >> #7 0x0000555555f80764 in bdrv_reset_dirty_bitmap_locked (bitmap=0x55555850a660, offset=0, bytes=1048576) at ../block/dirty-bitmap.c:563 >> #8 0x0000555555f807ab in bdrv_reset_dirty_bitmap (bitmap=0x55555850a660, offset=0, bytes=1048576) at ../block/dirty-bitmap.c:570 >> #9 0x0000555555f7bb16 in cbw_co_pdiscard_snapshot (bs=0x5555581a7f60, offset=0, bytes=1048576) at ../block/copy-before-write.c:330 >> #10 0x0000555555f8d00a in bdrv_co_pdiscard_snapshot (bs=0x5555581a7f60, offset=0, bytes=1048576) at ../block/io.c:3734 >> #11 0x0000555555fd2380 in snapshot_access_co_pdiscard (bs=0x5555582b4f60, offset=0, bytes=1048576) at ../block/snapshot-access.c:55 >> #12 0x0000555555f8b65d in bdrv_co_pdiscard (child=0x5555584fe790, offset=0, bytes=1048576) at ../block/io.c:3144 >> #13 0x0000555555f78650 in block_copy_task_entry (task=0x555557f588f0) at ../block/block-copy.c:597 > > My guess for the cause is that in block_copy_calculate_cluster_size() we > only look at the target. But now that we need to discard the source, > we'll also need to consider that for the calculation? > Just querying the source and picking the maximum won't work either, because snapshot-access does not currently implement .bdrv_co_get_info and because copy-before-write (doesn't implement .bdrv_co_get_info and is a filter) will just return the info of its file child. But the discard will go to the target child. If I do 1. .bdrv_co_get_info in snapshot-access: return info from file child 2. .bdrv_co_get_info in copy-before-write: return maximum cluster_size from file child and target child 3. block_copy_calculate_cluster_size: return maximum from source and target then the issue does go away, but I don't know if that's not violating any assumptions and probably there's a better way to avoid the issue? Best Regards, Fiona
On 25.01.24 15:47, Fiona Ebner wrote: > Am 24.01.24 um 16:03 schrieb Fiona Ebner: >> Am 17.01.24 um 17:07 schrieb Vladimir Sementsov-Ogievskiy: >>> 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. >>> >>> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru> >> >> Ran into another issue when the cluster_size of the fleecing image is >> larger than for the backup target, e.g. >> >>> #!/bin/bash >>> rm /tmp/fleecing.qcow2 >>> ./qemu-img create /tmp/disk.qcow2 -f qcow2 1G >>> ./qemu-img create /tmp/fleecing.qcow2 -o cluster_size=2M -f qcow2 1G >>> ./qemu-img create /tmp/backup.qcow2 -f qcow2 1G >>> ./qemu-system-x86_64 --qmp stdio \ >>> --blockdev qcow2,node-name=node0,file.driver=file,file.filename=/tmp/disk.qcow2 \ >>> --blockdev qcow2,node-name=node1,file.driver=file,file.filename=/tmp/fleecing.qcow2,discard=unmap \ >>> --blockdev qcow2,node-name=node2,file.driver=file,file.filename=/tmp/backup.qcow2 \ >>> <<EOF >>> {"execute": "qmp_capabilities"} >>> {"execute": "blockdev-add", "arguments": { "driver": "copy-before-write", "file": "node0", "target": "node1", "node-name": "node3" } } >>> {"execute": "blockdev-add", "arguments": { "driver": "snapshot-access", "file": "node3", "discard": "unmap", "node-name": "snap0" } } >>> {"execute": "blockdev-backup", "arguments": { "device": "snap0", "target": "node2", "sync": "full", "job-id": "backup0", "discard-source": true } } >>> EOF >> >> will fail with >> >>> qemu-system-x86_64: ../util/hbitmap.c:570: hbitmap_reset: Assertion `QEMU_IS_ALIGNED(count, gran) || (start + count == hb->orig_size)' failed. >> >> Backtrace shows the assert happens while discarding, when resetting the >> BDRVCopyBeforeWriteState access_bitmap >> > #6 0x0000555556142a2a in hbitmap_reset (hb=0x555557e01b80, start=0, >> count=1048576) at ../util/hbitmap.c:570 >>> #7 0x0000555555f80764 in bdrv_reset_dirty_bitmap_locked (bitmap=0x55555850a660, offset=0, bytes=1048576) at ../block/dirty-bitmap.c:563 >>> #8 0x0000555555f807ab in bdrv_reset_dirty_bitmap (bitmap=0x55555850a660, offset=0, bytes=1048576) at ../block/dirty-bitmap.c:570 >>> #9 0x0000555555f7bb16 in cbw_co_pdiscard_snapshot (bs=0x5555581a7f60, offset=0, bytes=1048576) at ../block/copy-before-write.c:330 >>> #10 0x0000555555f8d00a in bdrv_co_pdiscard_snapshot (bs=0x5555581a7f60, offset=0, bytes=1048576) at ../block/io.c:3734 >>> #11 0x0000555555fd2380 in snapshot_access_co_pdiscard (bs=0x5555582b4f60, offset=0, bytes=1048576) at ../block/snapshot-access.c:55 >>> #12 0x0000555555f8b65d in bdrv_co_pdiscard (child=0x5555584fe790, offset=0, bytes=1048576) at ../block/io.c:3144 >>> #13 0x0000555555f78650 in block_copy_task_entry (task=0x555557f588f0) at ../block/block-copy.c:597 >> >> My guess for the cause is that in block_copy_calculate_cluster_size() we >> only look at the target. But now that we need to discard the source, >> we'll also need to consider that for the calculation? >> > > Just querying the source and picking the maximum won't work either, > because snapshot-access does not currently implement .bdrv_co_get_info > and because copy-before-write (doesn't implement .bdrv_co_get_info and > is a filter) will just return the info of its file child. But the > discard will go to the target child. > > If I do > > 1. .bdrv_co_get_info in snapshot-access: return info from file child > 2. .bdrv_co_get_info in copy-before-write: return maximum cluster_size > from file child and target child > 3. block_copy_calculate_cluster_size: return maximum from source and target > > then the issue does go away, but I don't know if that's not violating > any assumptions and probably there's a better way to avoid the issue? > Hmm. Taking maximum is not optimal for usual case without discard-source: user may want to work in smaller granularity than source, to save disk space. In case with discarding we have two possibilities: - either take larger granularity for the whole process like you propose (but this will need and option for CBW?) - or, fix discarding bitmap in CBW to work like normal discard: it should be aligned down. This will lead actually to discard-source option doing nothing.. == But why do you want fleecing image with larger granularity? Is that a real case or just experimenting? Still we should fix assertion anyway. I think: 1. fix discarding bitmap to make aligning-down (will do that for v3) 2. if we need another logic for block_copy_calculate_cluster_size() it should be an option. May be explicit "copy-cluster-size" or "granularity" option for CBW driver and for backup job. And we'll just check that given cluster-size is power of two >= target_size.
On 19.01.24 17:46, Fiona Ebner wrote: > Am 17.01.24 um 17:07 schrieb Vladimir Sementsov-Ogievskiy: >> 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. >> >> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru> > > Unfortunately, setting BLK_PERM_WRITE unconditionally breaks > blockdev-backup for a read-only node (even when not using discard-source): Ohh, right. So, that's the place when we have to somehow pass through discrard-souce option to CBW filter, so that it know that WRITE permission is needed. Will try in v3. Thanks again for testing! > >> #!/bin/bash >> ./qemu-img create /tmp/disk.raw -f raw 1G >> ./qemu-img create /tmp/backup.raw -f raw 1G >> ./qemu-system-x86_64 --qmp stdio \ >> --blockdev raw,node-name=node0,file.driver=file,file.filename=/tmp/disk.raw,read-only=true \ >> --blockdev raw,node-name=node1,file.driver=file,file.filename=/tmp/backup.raw \ >> <<EOF >> {"execute": "qmp_capabilities"} >> {"execute": "blockdev-backup", "arguments": { "device": "node0", "target": "node1", "sync": "full", "job-id": "backup0" } } >> EOF > > The above works before applying this patch, but leads to an error > afterwards: > >> {"error": {"class": "GenericError", "desc": "Block node is read-only"}} > > Best Regards, > Fiona >
Am 25.01.24 um 18:22 schrieb Vladimir Sementsov-Ogievskiy: > > Hmm. Taking maximum is not optimal for usual case without > discard-source: user may want to work in smaller granularity than > source, to save disk space. > > In case with discarding we have two possibilities: > > - either take larger granularity for the whole process like you propose > (but this will need and option for CBW?) > - or, fix discarding bitmap in CBW to work like normal discard: it > should be aligned down. This will lead actually to discard-source option > doing nothing.. > > == > But why do you want fleecing image with larger granularity? Is that a > real case or just experimenting? Still we should fix assertion anyway. > Yes, it's a real use case. We do support different storage types and want to allow users to place the fleecing image on a different storage than the original image for flexibility. I ran into the issue when backing up to a target with 1 MiB cluster_size while using a fleecing image on RBD (which has 4 MiB cluster_size by default). In theory, I guess I could look into querying the cluster_size of the backup target and trying to allocate the fleecing image with a small enough cluster_size. But not sure if that would work on all storage combinations, and would require teaching our storage plugin API (which also supports third-party plugins) to perform allocation with a specific cluster size. So not an ideal solution for us. > I think: > > 1. fix discarding bitmap to make aligning-down (will do that for v3) > Thanks! > 2. if we need another logic for block_copy_calculate_cluster_size() it > should be an option. May be explicit "copy-cluster-size" or > "granularity" option for CBW driver and for backup job. And we'll just > check that given cluster-size is power of two >= target_size. > I'll try to implement point 2. That should resolve the issue for our use case. Best Regards, Fiona
diff --git a/block/backup.c b/block/backup.c index ec29d6b810..0c86b5be55 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, @@ -491,7 +491,8 @@ BlockJob *backup_job_create(const char *job_id, BlockDriverState *bs, job->len = len; job->perf = *perf; - block_copy_set_copy_opts(bcs, perf->use_copy_range, compress); + block_copy_set_copy_opts(bcs, perf->use_copy_range, compress, + discard_source); block_copy_set_progress_meter(bcs, &job->common.job.progress); block_copy_set_speed(bcs, speed); diff --git a/block/block-copy.c b/block/block-copy.c index 8fca2c3698..eebf643e86 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; /* @@ -282,11 +283,12 @@ static uint32_t block_copy_max_transfer(BdrvChild *source, BdrvChild *target) } void block_copy_set_copy_opts(BlockCopyState *s, bool use_copy_range, - bool compress) + bool compress, bool discard_source) { /* Keep BDRV_REQ_SERIALISING set (or not set) in block_copy_state_new() */ s->write_flags = (s->write_flags & BDRV_REQ_SERIALISING) | (compress ? BDRV_REQ_WRITE_COMPRESSED : 0); + s->discard_source = discard_source; if (s->max_transfer < s->cluster_size) { /* @@ -418,7 +420,7 @@ BlockCopyState *block_copy_state_new(BdrvChild *source, BdrvChild *target, cluster_size), }; - block_copy_set_copy_opts(s, false, false); + block_copy_set_copy_opts(s, false, false, false); ratelimit_init(&s->rate_limit); qemu_co_mutex_init(&s->lock); @@ -589,6 +591,12 @@ 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 4cd9b7d91e..b208a80ade 100644 --- a/block/copy-before-write.c +++ b/block/copy-before-write.c @@ -370,7 +370,7 @@ cbw_child_perm(BlockDriverState *bs, BdrvChild *c, BdrvChildRole role, * works even if source node does not have any parents before backup * start */ - *nperm = *nperm | BLK_PERM_CONSISTENT_READ; + *nperm = *nperm | BLK_PERM_CONSISTENT_READ | BLK_PERM_WRITE; *nshared &= ~(BLK_PERM_WRITE | BLK_PERM_RESIZE); } } diff --git a/block/replication.c b/block/replication.c index ca6bd0a720..0415a5e8b7 100644 --- a/block/replication.c +++ b/block/replication.c @@ -582,8 +582,8 @@ 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 3a5e7222ec..aa64382f82 100644 --- a/blockdev.c +++ b/blockdev.c @@ -2713,7 +2713,7 @@ 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-copy.h b/include/block/block-copy.h index 8b41643bfa..9555de2562 100644 --- a/include/block/block-copy.h +++ b/include/block/block-copy.h @@ -31,7 +31,7 @@ BlockCopyState *block_copy_state_new(BdrvChild *source, BdrvChild *target, /* Function should be called prior any actual copy request */ void block_copy_set_copy_opts(BlockCopyState *s, bool use_copy_range, - bool compress); + bool compress, bool discard_source); void block_copy_set_progress_meter(BlockCopyState *s, ProgressMeter *pm); void block_copy_state_free(BlockCopyState *s); diff --git a/include/block/block_int-global-state.h b/include/block/block_int-global-state.h index ef31c58bb3..563aabf012 100644 --- a/include/block/block_int-global-state.h +++ b/include/block/block_int-global-state.h @@ -187,7 +187,7 @@ 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 ca390c5700..1735769f9f 100644 --- a/qapi/block-core.json +++ b/qapi/block-core.json @@ -1599,6 +1599,9 @@ # 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: @@ -1620,6 +1623,7 @@ '*on-target-error': 'BlockdevOnError', '*auto-finalize': 'bool', '*auto-dismiss': 'bool', '*filter-node-name': 'str', + '*discard-source': 'bool', '*x-perf': { 'type': 'BackupPerf', 'features': [ 'unstable' ] } } }
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. Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru> --- block/backup.c | 5 +++-- block/block-copy.c | 12 ++++++++++-- block/copy-before-write.c | 2 +- block/replication.c | 4 ++-- blockdev.c | 2 +- include/block/block-copy.h | 2 +- include/block/block_int-global-state.h | 2 +- qapi/block-core.json | 4 ++++ 8 files changed, 23 insertions(+), 10 deletions(-)