Hi Vladimir, hope I didn't miss a newer version of this series. I'm currently evaluating fleecing backup for Proxmox downstream, so I pulled in this series and wanted to let you know about two issues I encountered while testing. We are still based on 8.1, but if I'm not mistaken, they are still relevant:
Am 31.03.22 um 21:57 schrieb Vladimir Sementsov-Ogievskiy: > @@ -575,6 +577,10 @@ 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) { > + bdrv_co_pdiscard(s->source, t->req.offset, t->req.bytes); > + } > + > return ret; > } > If the image size is not aligned to the cluster size, passing t->req.bytes when calling bdrv_co_pdiscard() can lead to an assertion failure at the end of the image: > kvm: ../block/io.c:1982: bdrv_co_write_req_prepare: Assertion `offset + bytes > <= bs->total_sectors * BDRV_SECTOR_SIZE || child->perm & BLK_PERM_RESIZE' > failed. block_copy_do_copy() does have a line to clamp down: > int64_t nbytes = MIN(offset + bytes, s->len) - offset; If I do the same before calling bdrv_co_pdiscard(), the failure goes away. For the second one, the following code saw some changes since the series was sent: > diff --git a/block/copy-before-write.c b/block/copy-before-write.c > index 79cf12380e..3e77313a9a 100644 > --- a/block/copy-before-write.c > +++ b/block/copy-before-write.c > @@ -319,7 +319,7 @@ static void cbw_child_perm(BlockDriverState *bs, > BdrvChild *c, > bdrv_default_perms(bs, c, role, reopen_queue, > perm, shared, nperm, nshared); > > - *nperm = *nperm | BLK_PERM_CONSISTENT_READ; > + *nperm = *nperm | BLK_PERM_CONSISTENT_READ | BLK_PERM_WRITE; > *nshared &= ~(BLK_PERM_WRITE | BLK_PERM_RESIZE); > } > } It's now: > bdrv_default_perms(bs, c, role, reopen_queue, > perm, shared, nperm, nshared); > > if (!QLIST_EMPTY(&bs->parents)) { > if (perm & BLK_PERM_WRITE) { > *nperm = *nperm | BLK_PERM_CONSISTENT_READ; > } > *nshared &= ~(BLK_PERM_WRITE | BLK_PERM_RESIZE); > } So I wasn't sure how to adapt the patch: - If setting BLK_PERM_WRITE unconditionally, it seems to break usual drive-backup (with no fleecing set up): > permissions 'write' are both required by node '#block691' (uses node > '#block151' as 'file' child) and unshared by block device 'drive-scsi0' (uses > node '#block151' as 'root' child). - If I only do it within the if block, it doesn't work when I try to set up fleecing, because bs->parents is empty for me, i.e. when passing the snapshot-access node to backup_job_create() while the usual cbw for backup is appended. I should note I'm doing it manually in a custom QMP command, not in a transaction (which requires the not-yet-merged blockdev-replace AFAIU). Not sure if I'm doing something wrong, but maybe what you wrote in the commit message is necessary after all? > Alternative is to pass > an option to bdrv_cbw_append(), add some internal open-option for > copy-before-write filter to require WRITE permission only for backup > with discard-source=true. But I'm not sure it worth the complexity. Best Regards, Fiona