| Message ID | 20190805145541.3731-1-mreitz@redhat.com |
|---|---|
| State | New |
| Headers | show |
| Series | [v2] mirror: Only mirror granularity-aligned chunks | expand |
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: qemu-stable@nongnu.org > Signed-off-by: Max Reitz <mreitz@redhat.com> > --- > 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? > + > s->dirty_bitmap = bdrv_create_dirty_bitmap(bs, granularity, NULL, errp); > if (!s->dirty_bitmap) { > goto fail; >
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: qemu-stable@nongnu.org >> Signed-off-by: Max Reitz <mreitz@redhat.com> >> --- >> 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? Max >> + >> s->dirty_bitmap = bdrv_create_dirty_bitmap(bs, granularity, NULL, errp); >> if (!s->dirty_bitmap) { >> goto fail; >> > >
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: qemu-stable@nongnu.org >>> Signed-off-by: Max Reitz <mreitz@redhat.com> >>> --- >>> 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
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); + s->dirty_bitmap = bdrv_create_dirty_bitmap(bs, granularity, NULL, errp); if (!s->dirty_bitmap) { goto fail;
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: qemu-stable@nongnu.org Signed-off-by: Max Reitz <mreitz@redhat.com> --- v2: Fix the placement of our bdrv_refresh_limits() call [Vladimir] --- block/mirror.c | 25 +++++++++++++++++++++++++ 1 file changed, 25 insertions(+)