| Message ID | 20180906130225.5118-5-jsnow@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | jobs: Job Exit Refactoring Pt 2 | expand |
On Thu, Sep 06, 2018 at 09:02:13AM -0400, John Snow wrote: > Use the component callbacks; prepare, abort, and clean. > > NB: prepare is only called when the job has not yet failed; > and abort can be called after prepare. > > complete -> prepare -> abort -> clean > complete -> abort -> clean > > During refactor, a potential problem with bdrv_drop_intermediate > was identified, The patched behavior is no worse than the pre-patch > behavior, so leave a FIXME for now to be fixed in a future patch. > > Signed-off-by: John Snow <jsnow@redhat.com> > Reviewed-by: Max Reitz <mreitz@redhat.com> Reviewed-by: Jeff Cody <jcody@redhat.com> > --- > block/commit.c | 92 ++++++++++++++++++++++++++++++++-------------------------- > 1 file changed, 51 insertions(+), 41 deletions(-) > > diff --git a/block/commit.c b/block/commit.c > index b6e8969877..a2da5740b0 100644 > --- a/block/commit.c > +++ b/block/commit.c > @@ -36,6 +36,7 @@ typedef struct CommitBlockJob { > BlockDriverState *commit_top_bs; > BlockBackend *top; > BlockBackend *base; > + BlockDriverState *base_bs; > BlockdevOnError on_error; > int base_flags; > char *backing_file_str; > @@ -68,61 +69,67 @@ static int coroutine_fn commit_populate(BlockBackend *bs, BlockBackend *base, > return 0; > } > > -static void commit_exit(Job *job) > +static int commit_prepare(Job *job) > { > CommitBlockJob *s = container_of(job, CommitBlockJob, common.job); > - BlockJob *bjob = &s->common; > - BlockDriverState *top = blk_bs(s->top); > - BlockDriverState *base = blk_bs(s->base); > - BlockDriverState *commit_top_bs = s->commit_top_bs; > - bool remove_commit_top_bs = false; > - > - /* Make sure commit_top_bs and top stay around until bdrv_replace_node() */ > - bdrv_ref(top); > - bdrv_ref(commit_top_bs); > > /* Remove base node parent that still uses BLK_PERM_WRITE/RESIZE before > * the normal backing chain can be restored. */ > blk_unref(s->base); > + s->base = NULL; > > - if (!job_is_cancelled(job) && job->ret == 0) { > - /* success */ > - job->ret = bdrv_drop_intermediate(s->commit_top_bs, base, > - s->backing_file_str); > - } else { > - /* XXX Can (or should) we somehow keep 'consistent read' blocked even > - * after the failed/cancelled commit job is gone? If we already wrote > - * something to base, the intermediate images aren't valid any more. */ > - remove_commit_top_bs = true; > + /* FIXME: bdrv_drop_intermediate treats total failures and partial failures > + * identically. Further work is needed to disambiguate these cases. */ > + return bdrv_drop_intermediate(s->commit_top_bs, s->base_bs, > + s->backing_file_str); > +} > + > +static void commit_abort(Job *job) > +{ > + CommitBlockJob *s = container_of(job, CommitBlockJob, common.job); > + BlockDriverState *top_bs = blk_bs(s->top); > + > + /* Make sure commit_top_bs and top stay around until bdrv_replace_node() */ > + bdrv_ref(top_bs); > + bdrv_ref(s->commit_top_bs); > + > + if (s->base) { > + blk_unref(s->base); > } > > + /* free the blockers on the intermediate nodes so that bdrv_replace_nodes > + * can succeed */ > + block_job_remove_all_bdrv(&s->common); > + > + /* If bdrv_drop_intermediate() failed (or was not invoked), remove the > + * commit filter driver from the backing chain now. Do this as the final > + * step so that the 'consistent read' permission can be granted. > + * > + * XXX Can (or should) we somehow keep 'consistent read' blocked even > + * after the failed/cancelled commit job is gone? If we already wrote > + * something to base, the intermediate images aren't valid any more. */ > + bdrv_child_try_set_perm(s->commit_top_bs->backing, 0, BLK_PERM_ALL, > + &error_abort); > + bdrv_replace_node(s->commit_top_bs, backing_bs(s->commit_top_bs), > + &error_abort); > + > + bdrv_unref(s->commit_top_bs); > + bdrv_unref(top_bs); > +} > + > +static void commit_clean(Job *job) > +{ > + CommitBlockJob *s = container_of(job, CommitBlockJob, common.job); > + > /* restore base open flags here if appropriate (e.g., change the base back > * to r/o). These reopens do not need to be atomic, since we won't abort > * even on failure here */ > - if (s->base_flags != bdrv_get_flags(base)) { > - bdrv_reopen(base, s->base_flags, NULL); > + if (s->base_flags != bdrv_get_flags(s->base_bs)) { > + bdrv_reopen(s->base_bs, s->base_flags, NULL); > } > + > g_free(s->backing_file_str); > blk_unref(s->top); > - > - /* If there is more than one reference to the job (e.g. if called from > - * job_finish_sync()), job_completed() won't free it and therefore the > - * blockers on the intermediate nodes remain. This would cause > - * bdrv_set_backing_hd() to fail. */ > - block_job_remove_all_bdrv(bjob); > - > - /* If bdrv_drop_intermediate() didn't already do that, remove the commit > - * filter driver from the backing chain. Do this as the final step so that > - * the 'consistent read' permission can be granted. */ > - if (remove_commit_top_bs) { > - bdrv_child_try_set_perm(commit_top_bs->backing, 0, BLK_PERM_ALL, > - &error_abort); > - bdrv_replace_node(commit_top_bs, backing_bs(commit_top_bs), > - &error_abort); > - } > - > - bdrv_unref(commit_top_bs); > - bdrv_unref(top); > } > > static int coroutine_fn commit_run(Job *job, Error **errp) > @@ -211,7 +218,9 @@ static const BlockJobDriver commit_job_driver = { > .user_resume = block_job_user_resume, > .drain = block_job_drain, > .run = commit_run, > - .exit = commit_exit, > + .prepare = commit_prepare, > + .abort = commit_abort, > + .clean = commit_clean > }, > }; > > @@ -345,6 +354,7 @@ void commit_start(const char *job_id, BlockDriverState *bs, > if (ret < 0) { > goto fail; > } > + s->base_bs = base; > > /* Required permissions are already taken with block_job_add_bdrv() */ > s->top = blk_new(0, BLK_PERM_ALL); > -- > 2.14.4 >
On 2018-09-06 15:02, John Snow wrote: > Use the component callbacks; prepare, abort, and clean. > > NB: prepare is only called when the job has not yet failed; > and abort can be called after prepare. > > complete -> prepare -> abort -> clean > complete -> abort -> clean > > During refactor, a potential problem with bdrv_drop_intermediate > was identified, The patched behavior is no worse than the pre-patch (s/T/t/) (Max) > behavior, so leave a FIXME for now to be fixed in a future patch. > > Signed-off-by: John Snow <jsnow@redhat.com> > Reviewed-by: Max Reitz <mreitz@redhat.com> > --- > block/commit.c | 92 ++++++++++++++++++++++++++++++++-------------------------- > 1 file changed, 51 insertions(+), 41 deletions(-)
diff --git a/block/commit.c b/block/commit.c index b6e8969877..a2da5740b0 100644 --- a/block/commit.c +++ b/block/commit.c @@ -36,6 +36,7 @@ typedef struct CommitBlockJob { BlockDriverState *commit_top_bs; BlockBackend *top; BlockBackend *base; + BlockDriverState *base_bs; BlockdevOnError on_error; int base_flags; char *backing_file_str; @@ -68,61 +69,67 @@ static int coroutine_fn commit_populate(BlockBackend *bs, BlockBackend *base, return 0; } -static void commit_exit(Job *job) +static int commit_prepare(Job *job) { CommitBlockJob *s = container_of(job, CommitBlockJob, common.job); - BlockJob *bjob = &s->common; - BlockDriverState *top = blk_bs(s->top); - BlockDriverState *base = blk_bs(s->base); - BlockDriverState *commit_top_bs = s->commit_top_bs; - bool remove_commit_top_bs = false; - - /* Make sure commit_top_bs and top stay around until bdrv_replace_node() */ - bdrv_ref(top); - bdrv_ref(commit_top_bs); /* Remove base node parent that still uses BLK_PERM_WRITE/RESIZE before * the normal backing chain can be restored. */ blk_unref(s->base); + s->base = NULL; - if (!job_is_cancelled(job) && job->ret == 0) { - /* success */ - job->ret = bdrv_drop_intermediate(s->commit_top_bs, base, - s->backing_file_str); - } else { - /* XXX Can (or should) we somehow keep 'consistent read' blocked even - * after the failed/cancelled commit job is gone? If we already wrote - * something to base, the intermediate images aren't valid any more. */ - remove_commit_top_bs = true; + /* FIXME: bdrv_drop_intermediate treats total failures and partial failures + * identically. Further work is needed to disambiguate these cases. */ + return bdrv_drop_intermediate(s->commit_top_bs, s->base_bs, + s->backing_file_str); +} + +static void commit_abort(Job *job) +{ + CommitBlockJob *s = container_of(job, CommitBlockJob, common.job); + BlockDriverState *top_bs = blk_bs(s->top); + + /* Make sure commit_top_bs and top stay around until bdrv_replace_node() */ + bdrv_ref(top_bs); + bdrv_ref(s->commit_top_bs); + + if (s->base) { + blk_unref(s->base); } + /* free the blockers on the intermediate nodes so that bdrv_replace_nodes + * can succeed */ + block_job_remove_all_bdrv(&s->common); + + /* If bdrv_drop_intermediate() failed (or was not invoked), remove the + * commit filter driver from the backing chain now. Do this as the final + * step so that the 'consistent read' permission can be granted. + * + * XXX Can (or should) we somehow keep 'consistent read' blocked even + * after the failed/cancelled commit job is gone? If we already wrote + * something to base, the intermediate images aren't valid any more. */ + bdrv_child_try_set_perm(s->commit_top_bs->backing, 0, BLK_PERM_ALL, + &error_abort); + bdrv_replace_node(s->commit_top_bs, backing_bs(s->commit_top_bs), + &error_abort); + + bdrv_unref(s->commit_top_bs); + bdrv_unref(top_bs); +} + +static void commit_clean(Job *job) +{ + CommitBlockJob *s = container_of(job, CommitBlockJob, common.job); + /* restore base open flags here if appropriate (e.g., change the base back * to r/o). These reopens do not need to be atomic, since we won't abort * even on failure here */ - if (s->base_flags != bdrv_get_flags(base)) { - bdrv_reopen(base, s->base_flags, NULL); + if (s->base_flags != bdrv_get_flags(s->base_bs)) { + bdrv_reopen(s->base_bs, s->base_flags, NULL); } + g_free(s->backing_file_str); blk_unref(s->top); - - /* If there is more than one reference to the job (e.g. if called from - * job_finish_sync()), job_completed() won't free it and therefore the - * blockers on the intermediate nodes remain. This would cause - * bdrv_set_backing_hd() to fail. */ - block_job_remove_all_bdrv(bjob); - - /* If bdrv_drop_intermediate() didn't already do that, remove the commit - * filter driver from the backing chain. Do this as the final step so that - * the 'consistent read' permission can be granted. */ - if (remove_commit_top_bs) { - bdrv_child_try_set_perm(commit_top_bs->backing, 0, BLK_PERM_ALL, - &error_abort); - bdrv_replace_node(commit_top_bs, backing_bs(commit_top_bs), - &error_abort); - } - - bdrv_unref(commit_top_bs); - bdrv_unref(top); } static int coroutine_fn commit_run(Job *job, Error **errp) @@ -211,7 +218,9 @@ static const BlockJobDriver commit_job_driver = { .user_resume = block_job_user_resume, .drain = block_job_drain, .run = commit_run, - .exit = commit_exit, + .prepare = commit_prepare, + .abort = commit_abort, + .clean = commit_clean }, }; @@ -345,6 +354,7 @@ void commit_start(const char *job_id, BlockDriverState *bs, if (ret < 0) { goto fail; } + s->base_bs = base; /* Required permissions are already taken with block_job_add_bdrv() */ s->top = blk_new(0, BLK_PERM_ALL);