On 18.06.19 15:12, Vladimir Sementsov-Ogievskiy wrote: > 13.06.2019 1:09, Max Reitz wrote: >> This includes some permission limiting (for example, we only need to >> take the RESIZE permission for active commits where the base is smaller >> than the top). >> >> Signed-off-by: Max Reitz <mre...@redhat.com> > > ohm, unfortunately I'm far from knowing block/mirror mechanics and interfaces > :(. > > still some comments below. > >> --- >> block/mirror.c | 110 +++++++++++++++++++++++++++++++++++++------------ >> blockdev.c | 47 +++++++++++++++++---- >> 2 files changed, 124 insertions(+), 33 deletions(-) >> >> diff --git a/block/mirror.c b/block/mirror.c >> index 4fa8f57c80..3d767e3030 100644 >> --- a/block/mirror.c >> +++ b/block/mirror.c >> @@ -660,8 +660,10 @@ static int mirror_exit_common(Job *job) >> &error_abort); >> if (!abort && s->backing_mode == MIRROR_SOURCE_BACKING_CHAIN) { >> BlockDriverState *backing = s->is_none_mode ? src : s->base; >> - if (backing_bs(target_bs) != backing) { >> - bdrv_set_backing_hd(target_bs, backing, &local_err); >> + BlockDriverState *unfiltered_target = >> bdrv_skip_rw_filters(target_bs); >> + >> + if (bdrv_filtered_cow_bs(unfiltered_target) != backing) { >> + bdrv_set_backing_hd(unfiltered_target, backing, &local_err); >> if (local_err) { >> error_report_err(local_err); >> ret = -EPERM; >> @@ -711,7 +713,7 @@ static int mirror_exit_common(Job *job) >> block_job_remove_all_bdrv(bjob); >> bdrv_child_try_set_perm(mirror_top_bs->backing, 0, BLK_PERM_ALL, >> &error_abort); >> - bdrv_replace_node(mirror_top_bs, backing_bs(mirror_top_bs), >> &error_abort); >> + bdrv_replace_node(mirror_top_bs, mirror_top_bs->backing->bs, >> &error_abort); >> >> /* We just changed the BDS the job BB refers to (with either or both >> of the >> * bdrv_replace_node() calls), so switch the BB back so the cleanup >> does >> @@ -757,6 +759,7 @@ static int coroutine_fn mirror_dirty_init(MirrorBlockJob >> *s) >> { >> int64_t offset; >> BlockDriverState *base = s->base; >> + BlockDriverState *filtered_base; >> BlockDriverState *bs = s->mirror_top_bs->backing->bs; >> BlockDriverState *target_bs = blk_bs(s->target); >> int ret; >> @@ -795,6 +798,9 @@ static int coroutine_fn mirror_dirty_init(MirrorBlockJob >> *s) >> s->initial_zeroing_ongoing = false; >> } >> >> + /* Will be NULL if @base is not in @bs's chain */ > > Should we assert that not NULL?
Well, but it can be NULL. It is only non-NULL for active commit. > Hmm, so this is the way to "skip filters reverse from the base", yes? Worth > add a comment? We need this because bdrv_is_allocated() will report everything as allocated in a filter if it is allocated in its filtered child. So if we use @base in bdrv_is_allocated_above() and there is a filter on top of it, bdrv_is_allocated_above() will report everything as allocated that is allocated in @base (which we do not want). Therefor, we need to go to the topmost R/W filter on top of @base, so that bdrv_is_allocated_above() actually starts at the first COW chain element above @base. As for the comment, I thought the name “filtered base” would suffice, but sure. (“@filtered_base is the topmost node in the @bs-@base chain that is connected to @base only through filters” or something; plus the explanation why we need it.) >> + filtered_base = bdrv_filtered_cow_bs(bdrv_find_overlay(bs, base)); >> + >> /* First part, loop on the sectors and initialize the dirty bitmap. */ >> for (offset = 0; offset < s->bdev_length; ) { >> /* Just to make sure we are not exceeding int limit. */ [...] >> @@ -1583,15 +1590,42 @@ static void mirror_start_job(const char *job_id, >> BlockDriverState *bs, >> * In the case of active commit, things look a bit different, though, >> * because the target is an already populated backing file in active >> use. >> * We can allow anything except resize there.*/ >> + >> + target_perms = BLK_PERM_WRITE; >> + target_shared_perms = BLK_PERM_WRITE_UNCHANGED; >> + >> target_is_backing = bdrv_chain_contains(bs, target); > > don't you want skip filters here? actual target node may be in backing chain, > but has separate > filters above it I don’t quite understand. bdrv_chain_contains() iterates over the filter chain, so it shouldn’t matter whether there are filters above target or not. [...] >> @@ -1641,15 +1675,39 @@ static void mirror_start_job(const char *job_id, >> BlockDriverState *bs, >> /* In commit_active_start() all intermediate nodes disappear, so >> * any jobs in them must be blocked */ > > hmm, preexisting, it s/jobs/nodes/ I think the idea was that no other jobs may be run on intermediate nodes. (But by now it’s no longer just about jobs, so yes, should be s/jobs/nodes/. I don’t know whether I should squeeze that in here, though.) Max
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