On 05.08.19 17:14, Max Reitz wrote: > On 05.08.19 17:09, Vladimir Sementsov-Ogievskiy wrote: >> 05.08.2019 17:55, Max Reitz wrote: >>> In write-blocking mode, all writes to the top node directly go to the >>> target. We must only mirror chunks of data that are aligned to the >>> job's granularity, because that is how the dirty bitmap works. >>> Therefore, the request alignment for writes must be the job's >>> granularity (in write-blocking mode). >>> >>> Unfortunately, this forces all reads and writes to have the same >>> granularity (we only need this alignment for writes to the target, not >>> the source), but that is something to be fixed another time. >>> >>> Cc: [email protected] >>> Signed-off-by: Max Reitz <[email protected]> >>> --- >>> v2: Fix the placement of our bdrv_refresh_limits() call [Vladimir] >>> --- >>> block/mirror.c | 25 +++++++++++++++++++++++++ >>> 1 file changed, 25 insertions(+) >>> >>> diff --git a/block/mirror.c b/block/mirror.c >>> index 8cb75fb409..7f0ff01beb 100644 >>> --- a/block/mirror.c >>> +++ b/block/mirror.c >>> @@ -1481,6 +1481,15 @@ static void >>> bdrv_mirror_top_child_perm(BlockDriverState *bs, BdrvChild *c, >>> *nshared = BLK_PERM_ALL; >>> } >>> >>> +static void bdrv_mirror_top_refresh_limits(BlockDriverState *bs, Error >>> **errp) >>> +{ >>> + MirrorBDSOpaque *s = bs->opaque; >>> + >>> + if (s && s->job && s->job->copy_mode == >>> MIRROR_COPY_MODE_WRITE_BLOCKING) { >>> + bs->bl.request_alignment = s->job->granularity; >>> + } >>> +} >>> + >>> /* Dummy node that provides consistent read to its users without >>> requiring it >>> * from its backing file and that allows writes on the backing file >>> chain. */ >>> static BlockDriver bdrv_mirror_top = { >>> @@ -1493,6 +1502,7 @@ static BlockDriver bdrv_mirror_top = { >>> .bdrv_co_block_status = bdrv_co_block_status_from_backing, >>> .bdrv_refresh_filename = bdrv_mirror_top_refresh_filename, >>> .bdrv_child_perm = bdrv_mirror_top_child_perm, >>> + .bdrv_refresh_limits = bdrv_mirror_top_refresh_limits, >>> }; >>> >>> static BlockJob *mirror_start_job( >>> @@ -1637,6 +1647,21 @@ static BlockJob *mirror_start_job( >>> s->should_complete = true; >>> } >>> >>> + /* >>> + * Must be called before we start tracking writes, but after >>> + * >>> + * ((MirrorBlockJob *) >>> + * ((MirrorBDSOpaque *) >>> + * mirror_top_bs->opaque >>> + * )->job >>> + * )->copy_mode >>> + * >>> + * has the correct value. >>> + * (We start tracking writes as of the following >>> + * bdrv_create_dirty_bitmap() call.) >>> + */ >>> + bdrv_refresh_limits(mirror_top_bs, &error_abort); >> >> Also, I'm not sure about error_abort() here. why not use local_err and >> return NULL >> if failed? > > Why would it fail?
Ah. That’s why. Because the children can fail. That is so stupid. Like, really. Max
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