On 21.05.24 15:20, Fiona Ebner wrote:
From: John Snow <js...@redhat.com>for the mirror job. The bitmap's granularity is used as the job's granularity. The new @bitmap parameter is marked unstable in the QAPI and can currently only be used for @sync=full mode. Clusters initially dirty in the bitmap as well as new writes are copied to the target. Using block-dirty-bitmap-clear and block-dirty-bitmap-merge API, callers can simulate the three kinds of @BitmapSyncMode (which is used by backup): 1. always: default, just pass bitmap as working bitmap. 2. never: copy bitmap and pass copy to the mirror job. 3. on-success: copy bitmap and pass copy to the mirror job and if successful, merge bitmap into original afterwards. When the target image is a non-COW "diff image", i.e. one that was not used as the target of a previous mirror and the target image's cluster size is larger than the bitmap's granularity, or when @copy-mode=write-blocking is used, there is a pitfall, because the cluster in the target image will be allocated, but not contain all the data corresponding to the same region in the source image. An idea to avoid the limitation would be to mark clusters which are affected by unaligned writes and are not allocated in the target image dirty, so they would be copied fully later. However, for migration, the invariant that an actively synced mirror stays actively synced (unless an error happens) is useful, because without that invariant, migration might inactivate block devices when mirror still got work to do and run into an assertion failure [0]. Another approach would be to read the missing data from the source upon unaligned writes to be able to write the full target cluster instead. But certain targets like NBD do not allow querying the cluster size. To avoid limiting/breaking the use case of syncing to an existing target, which is arguably more common than the diff image use case, document the limitation in QAPI. This patch was originally based on one by Ma Haocong, but it has since been modified pretty heavily, first by John and then again by Fiona. [0]: https://lore.kernel.org/qemu-devel/1db7f571-cb7f-c293-04cc-cd856e060...@proxmox.com/ Suggested-by: Ma Haocong <mahaoc...@didichuxing.com> Signed-off-by: Ma Haocong <mahaoc...@didichuxing.com> Signed-off-by: John Snow <js...@redhat.com> [FG: switch to bdrv_dirty_bitmap_merge_internal] Signed-off-by: Fabian Grünbichler <f.gruenbich...@proxmox.com> Signed-off-by: Thomas Lamprecht <t.lampre...@proxmox.com> [FE: rebase for 9.1 get rid of bitmap mode parameter use caller-provided bitmap as working bitmap turn bitmap parameter experimental] Signed-off-by: Fiona Ebner <f.eb...@proxmox.com> Acked-by: Markus Armbruster <arm...@redhat.com> --- block/mirror.c | 80 +++++++++++++++++++++----- blockdev.c | 44 +++++++++++--- include/block/block_int-global-state.h | 5 +- qapi/block-core.json | 35 ++++++++++- tests/unit/test-block-iothread.c | 2 +- 5 files changed, 141 insertions(+), 25 deletions(-) diff --git a/block/mirror.c b/block/mirror.c index ca23d6ef65..d3d0698116 100644 --- a/block/mirror.c +++ b/block/mirror.c @@ -73,6 +73,11 @@ typedef struct MirrorBlockJob { size_t buf_size; int64_t bdev_length; unsigned long *cow_bitmap; + /* + * Whether the bitmap is created locally or provided by the caller (for + * incremental sync). + */ + bool dirty_bitmap_is_local; BdrvDirtyBitmap *dirty_bitmap; BdrvDirtyBitmapIter *dbi; uint8_t *buf; @@ -691,7 +696,11 @@ static int mirror_exit_common(Job *job) bdrv_unfreeze_backing_chain(mirror_top_bs, target_bs); }- bdrv_release_dirty_bitmap(s->dirty_bitmap);+ if (s->dirty_bitmap_is_local) { + bdrv_release_dirty_bitmap(s->dirty_bitmap); + } else { + bdrv_enable_dirty_bitmap(s->dirty_bitmap); + }/* Make sure that the source BDS doesn't go away during bdrv_replace_node,* before we can call bdrv_drained_end */ @@ -820,6 +829,16 @@ static void mirror_abort(Job *job) assert(ret == 0); }+/* Always called after commit/abort. */+static void mirror_clean(Job *job) +{ + MirrorBlockJob *s = container_of(job, MirrorBlockJob, common.job); + + if (!s->dirty_bitmap_is_local && s->dirty_bitmap) { + bdrv_dirty_bitmap_set_busy(s->dirty_bitmap, false); + }
why not do that in existing mirror_exit_common, where we already do release/enable?
+} +
-- Best regards, Vladimir
