| Message ID | 20170815081854.14568-2-el13635@mail.ntua.gr (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Tue, Aug 15, 2017 at 11:18:53AM +0300, Manos Pitsidianakis wrote: > block/backup.c currently uses before write notifiers on the targeted > node. We can create a filter node instead to intercept write requests > for the backup job on the BDS level, instead of the BlockBackend level. > > This is part of deprecating before write notifiers, which are hard coded > into the block layer. Block filter drivers are inserted into the graph > only when a feature is needed. This makes the block layer more modular > and reuses the block driver abstraction that is already present. > > Signed-off-by: Manos Pitsidianakis <el13635@mail.ntua.gr> > --- > block.c | 89 +++++++++++++++++-- > block/backup.c | 207 ++++++++++++++++++++++++++++++++++++++++----- > block/mirror.c | 7 +- > blockdev.c | 2 +- > include/block/block.h | 8 +- > tests/qemu-iotests/141.out | 2 +- > 6 files changed, 276 insertions(+), 39 deletions(-) > > diff --git a/block.c b/block.c > index 2de1c29eb3..81bd51b670 100644 > --- a/block.c > +++ b/block.c > @@ -2088,6 +2088,38 @@ static void bdrv_parent_cb_resize(BlockDriverState *bs) > } > > /* > + * Sets the file link of a BDS. A new reference is created; callers > + * which don't need their own reference any more must call bdrv_unref(). > + */ > +void bdrv_set_file(BlockDriverState *bs, BlockDriverState *file_bs, > + Error **errp) > +{ > + if (file_bs) { > + bdrv_ref(file_bs); > + } > + > + if (bs->file) { > + bdrv_unref_child(bs, bs->file); > + } > + > + if (!file_bs) { > + bs->file = NULL; > + goto out; > + } > + > + bs->file = bdrv_attach_child(bs, file_bs, "file", &child_file, > + errp); > + if (!bs->file) { > + bdrv_unref(file_bs); > + } > + > + bdrv_refresh_filename(bs); > + > +out: > + bdrv_refresh_limits(bs, NULL); > +} > + > +/* > * Sets the backing file link of a BDS. A new reference is created; callers > * which don't need their own reference any more must call bdrv_unref(). > */ > @@ -2355,12 +2387,12 @@ static BlockDriverState *bdrv_append_temp_snapshot(BlockDriverState *bs, > goto out; > } > > - /* bdrv_append() consumes a strong reference to bs_snapshot > + /* bdrv_append_backing() consumes a strong reference to bs_snapshot > * (i.e. it will call bdrv_unref() on it) even on error, so in > * order to be able to return one, we have to increase > * bs_snapshot's refcount here */ > bdrv_ref(bs_snapshot); > - bdrv_append(bs_snapshot, bs, &local_err); > + bdrv_append_backing(bs_snapshot, bs, &local_err); > if (local_err) { > error_propagate(errp, local_err); > bs_snapshot = NULL; > @@ -3142,7 +3174,7 @@ static bool should_update_child(BdrvChild *c, BlockDriverState *to) > return false; > } > > - if (c->role == &child_backing) { > + if (c->role == &child_backing || c->role == &child_file) { > /* If @from is a backing file of @to, ignore the child to avoid > * creating a loop. We only want to change the pointer of other > * parents. */ This may have unwanted side-effects. I think you're using is so that bdrv_set_file() + bdrv_replace_node() does not create a loop in the graph. That is okay if there is only one parent with child_file. If there are multiple parents with that role then it's not clear to me that they should all be skipped. > @@ -3213,6 +3245,45 @@ out: > } > > /* > + * Add new bs node at the top of a BDS chain while the chain is > + * live, while keeping required fields on the top layer. > + * > + * This will modify the BlockDriverState fields, and swap contents > + * between bs_new and bs_top. Both bs_new and bs_top are modified. > + * > + * bs_new must not be attached to a BlockBackend. > + * > + * bdrv_append_file() takes ownership of a bs_new reference and unrefs it > + * because that's what the callers commonly need. bs_new will be referenced by > + * the old parents of bs_top after bdrv_append_file() returns. If the caller > + * needs to keep a reference of its own, it must call bdrv_ref(). > + */ > +void bdrv_append_file(BlockDriverState *bs_new, BlockDriverState *bs_top, > + Error **errp) > +{ > + Error *local_err = NULL; > + > + bdrv_ref(bs_top); > + bdrv_set_file(bs_new, bs_top, &local_err); bdrv_set_file() takes its own reference so there's no need to call bdrv_ref(bs_top). But it would be more consistent with existing functions for bdrv_set_file() *not* to take a new reference. If you make that change then this bdrv_ref() is correct. > + if (local_err) { > + error_propagate(errp, local_err); > + bdrv_set_file(bs_new, NULL, &error_abort); If bdrv_set_file(bs_new, bs_top) failed, why is it necessary to set bs_new->file to NULL? bdrv_set_file() should guarantee that bs_new->file is either bs_top (on success) or the old value (on failure). Then the caller does not need to fix up bs_new->file on failure. > + goto out; > + } > + bdrv_replace_node(bs_top, bs_new, &local_err); > + if (local_err) { > + error_propagate(errp, local_err); > + goto out; > + } > + > + /* bs_new is now referenced by its new parents, we don't need the > + * additional reference any more. */ > +out: > + bdrv_unref(bs_top); > + bdrv_unref(bs_new); > +} > + > +/* > * Add new bs contents at the top of an image chain while the chain is > * live, while keeping required fields on the top layer. > * Plase introduce the bdrv_set_file() and bdrv_append_file() APIs in a separate patch from the backup block job changes. > @@ -3223,13 +3294,13 @@ out: > * > * This function does not create any image files. > * > - * bdrv_append() takes ownership of a bs_new reference and unrefs it because > - * that's what the callers commonly need. bs_new will be referenced by the old > - * parents of bs_top after bdrv_append() returns. If the caller needs to keep a > - * reference of its own, it must call bdrv_ref(). > + * bdrv_append_backing() takes ownership of a bs_new reference and unrefs it > + * because that's what the callers commonly need. bs_new will be referenced by > + * the old parents of bs_top after bdrv_append_backing() returns. If the caller > + * needs to keep a reference of its own, it must call bdrv_ref(). > */ > -void bdrv_append(BlockDriverState *bs_new, BlockDriverState *bs_top, > - Error **errp) > +void bdrv_append_backing(BlockDriverState *bs_new, BlockDriverState *bs_top, > + Error **errp) > { > Error *local_err = NULL; > Please change bdrv_append() to bdrv_append_backing() in a separate patch. > diff --git a/block/backup.c b/block/backup.c > index 504a089150..0828d522b6 100644 > --- a/block/backup.c > +++ b/block/backup.c > @@ -43,7 +43,7 @@ typedef struct BackupBlockJob { > unsigned long *done_bitmap; > int64_t cluster_size; > bool compress; > - NotifierWithReturn before_write; > + BlockDriverState *filter; > QLIST_HEAD(, CowRequest) inflight_reqs; > } BackupBlockJob; > > @@ -174,20 +174,6 @@ out: > return ret; > } > > -static int coroutine_fn backup_before_write_notify( > - NotifierWithReturn *notifier, > - void *opaque) > -{ > - BackupBlockJob *job = container_of(notifier, BackupBlockJob, before_write); > - BdrvTrackedRequest *req = opaque; > - > - assert(req->bs == blk_bs(job->common.blk)); > - assert(QEMU_IS_ALIGNED(req->offset, BDRV_SECTOR_SIZE)); > - assert(QEMU_IS_ALIGNED(req->bytes, BDRV_SECTOR_SIZE)); > - > - return backup_do_cow(job, req->offset, req->bytes, NULL, true); > -} > - > static void backup_set_speed(BlockJob *job, int64_t speed, Error **errp) > { > BackupBlockJob *s = container_of(job, BackupBlockJob, common); > @@ -202,7 +188,8 @@ static void backup_set_speed(BlockJob *job, int64_t speed, Error **errp) > static void backup_cleanup_sync_bitmap(BackupBlockJob *job, int ret) > { > BdrvDirtyBitmap *bm; > - BlockDriverState *bs = blk_bs(job->common.blk); > + BlockDriverState *bs = child_bs(blk_bs(job->common.blk)); > + assert(bs); > > if (ret < 0 || block_job_is_cancelled(&job->common)) { > /* Merge the successor back into the parent, delete nothing. */ > @@ -234,9 +221,31 @@ static void backup_abort(BlockJob *job) > static void backup_clean(BlockJob *job) > { > BackupBlockJob *s = container_of(job, BackupBlockJob, common); > + BlockDriverState *bs = child_bs(s->filter), > + *filter = s->filter; Please do not put multiple variable declarations with initializers in a single statement. It's easier to read like this: BlockDriverState *filter = s->filter; BlockDriverState *bs = child_bs(filter); > + > assert(s->target); > blk_unref(s->target); > s->target = NULL; > + > + /* make sure nothing goes away while removing filter */ > + bdrv_ref(filter); > + bdrv_ref(bs); > + bdrv_drained_begin(bs); > + > + block_job_remove_all_bdrv(job); > + bdrv_child_try_set_perm(filter->file, 0, BLK_PERM_ALL, > + &error_abort); > + bdrv_replace_node(filter, bs, &error_abort); > + > + blk_remove_bs(job->blk); > + blk_set_perm(job->blk, 0, BLK_PERM_ALL, &error_abort); > + blk_insert_bs(job->blk, filter, &error_abort); > + > + bdrv_drained_end(bs); > + bdrv_unref(filter); > + bdrv_unref(bs); > + s->filter = NULL; > } > > static void backup_attached_aio_context(BlockJob *job, AioContext *aio_context) > @@ -421,6 +430,18 @@ out: > return ret; > } > > +static void backup_top_enable(BackupBlockJob *job) > +{ > + BlockDriverState *bs = job->filter; > + bs->opaque = job; > +} > + > +static void backup_top_disable(BackupBlockJob *job) > +{ > + BlockDriverState *bs = job->filter; > + bs->opaque = NULL; > +} bs->opaque is a pointer that is managed by block.c. Drivers are not allowed to modify this pointer. You declared BlockDriver.instance_size = sizeof(BackupBlockJob *) but didn't use it. I guess this should be: static void backup_top_enable(BackupBlockJob *job) { BackupBlockJob **jobp = job->bs->opaque; *jobp = job; } static void backup_top_disable(BackupBlockJob *job) { BackupBlockJob **jobp = job->bs->opaque; *jobp = NULL; } ... static int coroutine_fn backup_top_co_pwritev(BlockDriverState *bs, uint64_t offset, uint64_t bytes, QEMUIOVector *qiov, int flags) { int ret = 0; BackupBlockJob *job = *(BackupBlockJob **)bs->opaque; if (job) { Alternatively filter->job can be used but that may be a legacy field that will be removed eventually. > + > static void coroutine_fn backup_run(void *opaque) > { > BackupBlockJob *job = opaque; > @@ -435,13 +456,12 @@ static void coroutine_fn backup_run(void *opaque) > job->done_bitmap = bitmap_new(DIV_ROUND_UP(job->common.len, > job->cluster_size)); > > - job->before_write.notify = backup_before_write_notify; > - bdrv_add_before_write_notifier(bs, &job->before_write); > + backup_top_enable(job); > > if (job->sync_mode == MIRROR_SYNC_MODE_NONE) { > while (!block_job_is_cancelled(&job->common)) { > - /* Yield until the job is cancelled. We just let our before_write > - * notify callback service CoW requests. */ > + /* Yield until the job is cancelled. We just let our backup_top > + * filter service CoW requests. */ > block_job_yield(&job->common); > } > } else if (job->sync_mode == MIRROR_SYNC_MODE_INCREMENTAL) { > @@ -507,8 +527,7 @@ static void coroutine_fn backup_run(void *opaque) > } > } > } > - > - notifier_with_return_remove(&job->before_write); > + backup_top_disable(job); > > /* wait until pending backup_do_cow() calls have completed */ > qemu_co_rwlock_wrlock(&job->flush_rwlock); > @@ -532,6 +551,124 @@ static const BlockJobDriver backup_job_driver = { > .drain = backup_drain, > }; > > +static int coroutine_fn backup_top_co_preadv(BlockDriverState *bs, > + uint64_t offset, > + uint64_t bytes, > + QEMUIOVector *qiov, int flags) > +{ > + return bdrv_co_preadv(bs->file, offset, bytes, qiov, flags); > +} > + > +static int coroutine_fn backup_top_co_pwritev(BlockDriverState *bs, > + uint64_t offset, > + uint64_t bytes, > + QEMUIOVector *qiov, int flags) > +{ > + int ret = 0; > + BackupBlockJob *job = bs->opaque; > + if (job) { > + assert(bs == blk_bs(job->common.blk)); > + assert(QEMU_IS_ALIGNED(offset, BDRV_SECTOR_SIZE)); > + assert(QEMU_IS_ALIGNED(bytes, BDRV_SECTOR_SIZE)); > + ret = backup_do_cow(job, offset, bytes, NULL, true); > + } > + > + return ret < 0 ? ret : bdrv_co_pwritev(bs->file, offset, bytes, > + qiov, flags); > +} > + > +static int coroutine_fn backup_top_co_pwrite_zeroes(BlockDriverState *bs, > + int64_t offset, > + int bytes, > + BdrvRequestFlags flags) > +{ > + int ret = 0; > + BackupBlockJob *job = bs->opaque; > + if (job) { > + assert(bs == blk_bs(job->common.blk)); > + assert(QEMU_IS_ALIGNED(offset, BDRV_SECTOR_SIZE)); > + assert(QEMU_IS_ALIGNED(bytes, BDRV_SECTOR_SIZE)); > + ret = backup_do_cow(job, offset, bytes, NULL, true); > + } > + > + return ret < 0 ? ret : bdrv_co_pwrite_zeroes(bs->file, offset, bytes, > + flags); > +} > + > +static int coroutine_fn backup_top_co_pdiscard(BlockDriverState *bs, > + int64_t offset, int bytes) > +{ > + int ret = 0; > + BackupBlockJob *job = bs->opaque; > + if (job) { > + assert(bs == blk_bs(job->common.blk)); > + assert(QEMU_IS_ALIGNED(offset, BDRV_SECTOR_SIZE)); > + assert(QEMU_IS_ALIGNED(bytes, BDRV_SECTOR_SIZE)); > + ret = backup_do_cow(job, offset, bytes, NULL, true); > + } > + > + return ret < 0 ? ret : bdrv_co_pdiscard(bs->file->bs, offset, bytes); > +} > + > +static int backup_top_co_flush(BlockDriverState *bs) > +{ > + return bdrv_co_flush(bs->file->bs); > +} > + > +static int backup_top_open(BlockDriverState *bs, QDict *options, > + int flags, Error **errp) > +{ > + return 0; > +} > + > +static void backup_top_close(BlockDriverState *bs) > +{ > +} > + > +static int64_t backup_top_getlength(BlockDriverState *bs) > +{ > + return bs->file ? bdrv_getlength(bs->file->bs) : 0; > +} > + > +static bool backup_recurse_is_first_non_filter(BlockDriverState *bs, > + BlockDriverState *candidate) > +{ > + return bdrv_recurse_is_first_non_filter(bs->file->bs, candidate); > +} > + > +static int64_t coroutine_fn backup_co_get_block_status(BlockDriverState *bs, > + int64_t sector_num, > + int nb_sectors, > + int *pnum, > + BlockDriverState **file) > +{ > + assert(bs->file && bs->file->bs); > + *pnum = nb_sectors; > + *file = bs->file->bs; > + return BDRV_BLOCK_RAW | BDRV_BLOCK_OFFSET_VALID | > + (sector_num << BDRV_SECTOR_BITS); > +} > +static BlockDriver backup_top = { > + .format_name = "backup-top", > + .instance_size = sizeof(BackupBlockJob *), > + > + .bdrv_open = backup_top_open, .bdrv_open may be NULL. There's no need to define this function. > + .bdrv_close = backup_top_close, > + > + .bdrv_co_flush = backup_top_co_flush, > + .bdrv_co_preadv = backup_top_co_preadv, > + .bdrv_co_pwritev = backup_top_co_pwritev, > + .bdrv_co_pwrite_zeroes = backup_top_co_pwrite_zeroes, > + .bdrv_co_pdiscard = backup_top_co_pdiscard, > + > + .bdrv_getlength = backup_top_getlength, > + .bdrv_child_perm = bdrv_filter_default_perms, > + .bdrv_recurse_is_first_non_filter = backup_recurse_is_first_non_filter, I think this is dead code since .is_filter = true. It will not be called. > + .bdrv_co_get_block_status = backup_co_get_block_status, > + > + .is_filter = true, > +}; > + > BlockJob *backup_job_create(const char *job_id, BlockDriverState *bs, > BlockDriverState *target, int64_t speed, > MirrorSyncMode sync_mode, BdrvDirtyBitmap *sync_bitmap, > @@ -545,6 +682,7 @@ BlockJob *backup_job_create(const char *job_id, BlockDriverState *bs, > int64_t len; > BlockDriverInfo bdi; > BackupBlockJob *job = NULL; > + BlockDriverState *filter = NULL; > int ret; > > assert(bs); > @@ -606,17 +744,33 @@ BlockJob *backup_job_create(const char *job_id, BlockDriverState *bs, > bdrv_get_device_name(bs)); > goto error; > } > + /* Setup before write filter */ > + filter = > + bdrv_new_open_driver(&backup_top, > + NULL, bdrv_get_flags(bs), NULL, &error_abort); > + filter->implicit = true; > + filter->total_sectors = bs->total_sectors; > + bdrv_set_aio_context(filter, bdrv_get_aio_context(bs)); > + > + /* Insert before write notifier in the BDS chain */ > + bdrv_ref(filter); > + bdrv_drained_begin(bs); > + bdrv_append_file(filter, bs, &error_abort); > + bdrv_drained_end(bs); > > /* job->common.len is fixed, so we can't allow resize */ > - job = block_job_create(job_id, &backup_job_driver, bs, > + job = block_job_create(job_id, &backup_job_driver, filter, > BLK_PERM_CONSISTENT_READ, > BLK_PERM_CONSISTENT_READ | BLK_PERM_WRITE | > BLK_PERM_WRITE_UNCHANGED | BLK_PERM_GRAPH_MOD, > speed, creation_flags, cb, opaque, errp); > + bdrv_unref(filter); > if (!job) { > goto error; > } > > + job->filter = filter; Is it okay to use filter here after bdrv_unref()? > + > /* The target must match the source in size, so no resize here either */ > job->target = blk_new(BLK_PERM_WRITE, > BLK_PERM_CONSISTENT_READ | BLK_PERM_WRITE | > @@ -675,6 +829,13 @@ BlockJob *backup_job_create(const char *job_id, BlockDriverState *bs, > if (job) { > backup_clean(&job->common); > block_job_early_fail(&job->common); > + } else { > + /* don't leak filter if job creation failed */ > + if (filter) { > + bdrv_child_try_set_perm(filter->file, 0, BLK_PERM_ALL, > + &error_abort); > + bdrv_replace_node(filter, bs, &error_abort); > + } > } > > return NULL; > diff --git a/block/mirror.c b/block/mirror.c > index e1a160e6ea..3044472fd4 100644 > --- a/block/mirror.c > +++ b/block/mirror.c > @@ -1174,11 +1174,12 @@ static void mirror_start_job(const char *job_id, BlockDriverState *bs, > mirror_top_bs->total_sectors = bs->total_sectors; > bdrv_set_aio_context(mirror_top_bs, bdrv_get_aio_context(bs)); > > - /* bdrv_append takes ownership of the mirror_top_bs reference, need to keep > - * it alive until block_job_create() succeeds even if bs has no parent. */ > + /* bdrv_append_backing() takes ownership of the mirror_top_bs reference, > + * need to keep it alive until block_job_create() succeeds even if bs has > + * no parent. */ > bdrv_ref(mirror_top_bs); > bdrv_drained_begin(bs); > - bdrv_append(mirror_top_bs, bs, &local_err); > + bdrv_append_backing(mirror_top_bs, bs, &local_err); > bdrv_drained_end(bs); > > if (local_err) { > diff --git a/blockdev.c b/blockdev.c > index 5c11c245b0..8e2fc6e64c 100644 > --- a/blockdev.c > +++ b/blockdev.c > @@ -1788,7 +1788,7 @@ static void external_snapshot_prepare(BlkActionState *common, > * can fail, so we need to do it in .prepare; undoing it for abort is > * always possible. */ > bdrv_ref(state->new_bs); > - bdrv_append(state->new_bs, state->old_bs, &local_err); > + bdrv_append_backing(state->new_bs, state->old_bs, &local_err); > if (local_err) { > error_propagate(errp, local_err); > return; > diff --git a/include/block/block.h b/include/block/block.h > index d1f03cb48b..744b50e734 100644 > --- a/include/block/block.h > +++ b/include/block/block.h > @@ -244,8 +244,10 @@ int bdrv_create(BlockDriver *drv, const char* filename, > QemuOpts *opts, Error **errp); > int bdrv_create_file(const char *filename, QemuOpts *opts, Error **errp); > BlockDriverState *bdrv_new(void); > -void bdrv_append(BlockDriverState *bs_new, BlockDriverState *bs_top, > - Error **errp); > +void bdrv_append_file(BlockDriverState *bs_new, BlockDriverState *bs_top, > + Error **errp); > +void bdrv_append_backing(BlockDriverState *bs_new, BlockDriverState *bs_top, > + Error **errp); > void bdrv_replace_node(BlockDriverState *from, BlockDriverState *to, > Error **errp); > > @@ -256,6 +258,8 @@ BdrvChild *bdrv_open_child(const char *filename, > BlockDriverState* parent, > const BdrvChildRole *child_role, > bool allow_none, Error **errp); > +void bdrv_set_file(BlockDriverState *bs, BlockDriverState *file_bs, > + Error **errp); > void bdrv_set_backing_hd(BlockDriverState *bs, BlockDriverState *backing_hd, > Error **errp); > int bdrv_open_backing_file(BlockDriverState *bs, QDict *parent_options, > diff --git a/tests/qemu-iotests/141.out b/tests/qemu-iotests/141.out > index 82e763b68d..cc653c317a 100644 > --- a/tests/qemu-iotests/141.out > +++ b/tests/qemu-iotests/141.out > @@ -9,7 +9,7 @@ Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1048576 backing_file=TEST_DIR/m. > {"return": {}} > Formatting 'TEST_DIR/o.IMGFMT', fmt=IMGFMT size=1048576 backing_file=TEST_DIR/t.IMGFMT backing_fmt=IMGFMT > {"return": {}} > -{"error": {"class": "GenericError", "desc": "Node drv0 is in use"}} > +{"error": {"class": "GenericError", "desc": "Block device drv0 is in use"}} > {"return": {}} > {"timestamp": {"seconds": TIMESTAMP, "microseconds": TIMESTAMP}, "event": "BLOCK_JOB_CANCELLED", "data": {"device": "job0", "len": 1048576, "offset": 0, "speed": 0, "type": "backup"}} > {"return": {}} > -- > 2.11.0 > >
On Wed, Aug 16, 2017 at 02:25:44PM +0100, Stefan Hajnoczi wrote: >On Tue, Aug 15, 2017 at 11:18:53AM +0300, Manos Pitsidianakis wrote: >> block/backup.c currently uses before write notifiers on the targeted >> node. We can create a filter node instead to intercept write requests >> for the backup job on the BDS level, instead of the BlockBackend level. >> >> This is part of deprecating before write notifiers, which are hard coded >> into the block layer. Block filter drivers are inserted into the graph >> only when a feature is needed. This makes the block layer more modular >> and reuses the block driver abstraction that is already present. >> >> Signed-off-by: Manos Pitsidianakis <el13635@mail.ntua.gr> >> --- >> block.c | 89 +++++++++++++++++-- >> block/backup.c | 207 ++++++++++++++++++++++++++++++++++++++++----- >> block/mirror.c | 7 +- >> blockdev.c | 2 +- >> include/block/block.h | 8 +- >> tests/qemu-iotests/141.out | 2 +- >> 6 files changed, 276 insertions(+), 39 deletions(-) >> >> diff --git a/block.c b/block.c >> index 2de1c29eb3..81bd51b670 100644 >> --- a/block.c >> +++ b/block.c >> @@ -2088,6 +2088,38 @@ static void bdrv_parent_cb_resize(BlockDriverState *bs) >> } >> >> /* >> + * Sets the file link of a BDS. A new reference is created; callers >> + * which don't need their own reference any more must call bdrv_unref(). >> + */ >> +void bdrv_set_file(BlockDriverState *bs, BlockDriverState *file_bs, >> + Error **errp) >> +{ >> + if (file_bs) { >> + bdrv_ref(file_bs); >> + } >> + >> + if (bs->file) { >> + bdrv_unref_child(bs, bs->file); >> + } >> + >> + if (!file_bs) { >> + bs->file = NULL; >> + goto out; >> + } >> + >> + bs->file = bdrv_attach_child(bs, file_bs, "file", &child_file, >> + errp); >> + if (!bs->file) { >> + bdrv_unref(file_bs); >> + } >> + >> + bdrv_refresh_filename(bs); >> + >> +out: >> + bdrv_refresh_limits(bs, NULL); >> +} >> + >> +/* >> * Sets the backing file link of a BDS. A new reference is created; callers >> * which don't need their own reference any more must call bdrv_unref(). >> */ >> @@ -2355,12 +2387,12 @@ static BlockDriverState *bdrv_append_temp_snapshot(BlockDriverState *bs, >> goto out; >> } >> >> - /* bdrv_append() consumes a strong reference to bs_snapshot >> + /* bdrv_append_backing() consumes a strong reference to bs_snapshot >> * (i.e. it will call bdrv_unref() on it) even on error, so in >> * order to be able to return one, we have to increase >> * bs_snapshot's refcount here */ >> bdrv_ref(bs_snapshot); >> - bdrv_append(bs_snapshot, bs, &local_err); >> + bdrv_append_backing(bs_snapshot, bs, &local_err); >> if (local_err) { >> error_propagate(errp, local_err); >> bs_snapshot = NULL; >> @@ -3142,7 +3174,7 @@ static bool should_update_child(BdrvChild *c, BlockDriverState *to) >> return false; >> } >> >> - if (c->role == &child_backing) { >> + if (c->role == &child_backing || c->role == &child_file) { >> /* If @from is a backing file of @to, ignore the child to avoid >> * creating a loop. We only want to change the pointer of other >> * parents. */ > >This may have unwanted side-effects. I think you're using is so that >bdrv_set_file() + bdrv_replace_node() does not create a loop in the >graph. That is okay if there is only one parent with child_file. If >there are multiple parents with that role then it's not clear to me that >they should all be skipped. I am afraid I don't understand what you're saying. What is the difference with the child_backing scenario here? In both cases we should update all from->parents children unless they also happen to be a child of `to`. If there are multiple parents with child_file, they are not skipped except for the ones where `to` is the parent. > >> @@ -3213,6 +3245,45 @@ out: >> } >> >> /* >> + * Add new bs node at the top of a BDS chain while the chain is >> + * live, while keeping required fields on the top layer. >> + * >> + * This will modify the BlockDriverState fields, and swap contents >> + * between bs_new and bs_top. Both bs_new and bs_top are modified. >> + * >> + * bs_new must not be attached to a BlockBackend. >> + * >> + * bdrv_append_file() takes ownership of a bs_new reference and unrefs it >> + * because that's what the callers commonly need. bs_new will be referenced by >> + * the old parents of bs_top after bdrv_append_file() returns. If the caller >> + * needs to keep a reference of its own, it must call bdrv_ref(). >> + */ >> +void bdrv_append_file(BlockDriverState *bs_new, BlockDriverState *bs_top, >> + Error **errp) >> +{ >> + Error *local_err = NULL; >> + >> + bdrv_ref(bs_top); >> + bdrv_set_file(bs_new, bs_top, &local_err); > >bdrv_set_file() takes its own reference so there's no need to call >bdrv_ref(bs_top). > >But it would be more consistent with existing functions for >bdrv_set_file() *not* to take a new reference. If you make that change >then this bdrv_ref() is correct. > >> + if (local_err) { >> + error_propagate(errp, local_err); >> + bdrv_set_file(bs_new, NULL, &error_abort); > >If bdrv_set_file(bs_new, bs_top) failed, why is it necessary to set >bs_new->file to NULL? > >bdrv_set_file() should guarantee that bs_new->file is either bs_top (on >success) or the old value (on failure). Then the caller does not need >to fix up bs_new->file on failure. I think the error paths got mixed here, bs_new->file should be set to NULL on bdrv_replace_node() failure. > >> + goto out; >> + } >> + bdrv_replace_node(bs_top, bs_new, &local_err); >> + if (local_err) { >> + error_propagate(errp, local_err); >> + goto out; >> + } >> + >> + /* bs_new is now referenced by its new parents, we don't need the >> + * additional reference any more. */ >> +out: >> + bdrv_unref(bs_top); >> + bdrv_unref(bs_new); >> +} >> + >> +/* >> * Add new bs contents at the top of an image chain while the chain is >> * live, while keeping required fields on the top layer. >> * > >Plase introduce the bdrv_set_file() and bdrv_append_file() APIs in a >separate patch from the backup block job changes. > >> @@ -3223,13 +3294,13 @@ out: >> * >> * This function does not create any image files. >> * >> - * bdrv_append() takes ownership of a bs_new reference and unrefs it because >> - * that's what the callers commonly need. bs_new will be referenced by the old >> - * parents of bs_top after bdrv_append() returns. If the caller needs to keep a >> - * reference of its own, it must call bdrv_ref(). >> + * bdrv_append_backing() takes ownership of a bs_new reference and unrefs it >> + * because that's what the callers commonly need. bs_new will be referenced by >> + * the old parents of bs_top after bdrv_append_backing() returns. If the caller >> + * needs to keep a reference of its own, it must call bdrv_ref(). >> */ >> -void bdrv_append(BlockDriverState *bs_new, BlockDriverState *bs_top, >> - Error **errp) >> +void bdrv_append_backing(BlockDriverState *bs_new, BlockDriverState *bs_top, >> + Error **errp) >> { >> Error *local_err = NULL; >> > >Please change bdrv_append() to bdrv_append_backing() in a separate >patch. > >> diff --git a/block/backup.c b/block/backup.c >> index 504a089150..0828d522b6 100644 >> --- a/block/backup.c >> +++ b/block/backup.c >> @@ -43,7 +43,7 @@ typedef struct BackupBlockJob { >> unsigned long *done_bitmap; >> int64_t cluster_size; >> bool compress; >> - NotifierWithReturn before_write; >> + BlockDriverState *filter; >> QLIST_HEAD(, CowRequest) inflight_reqs; >> } BackupBlockJob; >> >> @@ -174,20 +174,6 @@ out: >> return ret; >> } >> >> -static int coroutine_fn backup_before_write_notify( >> - NotifierWithReturn *notifier, >> - void *opaque) >> -{ >> - BackupBlockJob *job = container_of(notifier, BackupBlockJob, before_write); >> - BdrvTrackedRequest *req = opaque; >> - >> - assert(req->bs == blk_bs(job->common.blk)); >> - assert(QEMU_IS_ALIGNED(req->offset, BDRV_SECTOR_SIZE)); >> - assert(QEMU_IS_ALIGNED(req->bytes, BDRV_SECTOR_SIZE)); >> - >> - return backup_do_cow(job, req->offset, req->bytes, NULL, true); >> -} >> - >> static void backup_set_speed(BlockJob *job, int64_t speed, Error **errp) >> { >> BackupBlockJob *s = container_of(job, BackupBlockJob, common); >> @@ -202,7 +188,8 @@ static void backup_set_speed(BlockJob *job, int64_t speed, Error **errp) >> static void backup_cleanup_sync_bitmap(BackupBlockJob *job, int ret) >> { >> BdrvDirtyBitmap *bm; >> - BlockDriverState *bs = blk_bs(job->common.blk); >> + BlockDriverState *bs = child_bs(blk_bs(job->common.blk)); >> + assert(bs); >> >> if (ret < 0 || block_job_is_cancelled(&job->common)) { >> /* Merge the successor back into the parent, delete nothing. */ >> @@ -234,9 +221,31 @@ static void backup_abort(BlockJob *job) >> static void backup_clean(BlockJob *job) >> { >> BackupBlockJob *s = container_of(job, BackupBlockJob, common); >> + BlockDriverState *bs = child_bs(s->filter), >> + *filter = s->filter; > >Please do not put multiple variable declarations with initializers in a >single statement. It's easier to read like this: > > BlockDriverState *filter = s->filter; > BlockDriverState *bs = child_bs(filter); > >> + >> assert(s->target); >> blk_unref(s->target); >> s->target = NULL; >> + >> + /* make sure nothing goes away while removing filter */ >> + bdrv_ref(filter); >> + bdrv_ref(bs); >> + bdrv_drained_begin(bs); >> + >> + block_job_remove_all_bdrv(job); >> + bdrv_child_try_set_perm(filter->file, 0, BLK_PERM_ALL, >> + &error_abort); >> + bdrv_replace_node(filter, bs, &error_abort); >> + >> + blk_remove_bs(job->blk); >> + blk_set_perm(job->blk, 0, BLK_PERM_ALL, &error_abort); >> + blk_insert_bs(job->blk, filter, &error_abort); >> + >> + bdrv_drained_end(bs); >> + bdrv_unref(filter); >> + bdrv_unref(bs); >> + s->filter = NULL; >> } >> >> static void backup_attached_aio_context(BlockJob *job, AioContext *aio_context) >> @@ -421,6 +430,18 @@ out: >> return ret; >> } >> >> +static void backup_top_enable(BackupBlockJob *job) >> +{ >> + BlockDriverState *bs = job->filter; >> + bs->opaque = job; >> +} >> + >> +static void backup_top_disable(BackupBlockJob *job) >> +{ >> + BlockDriverState *bs = job->filter; >> + bs->opaque = NULL; >> +} > >bs->opaque is a pointer that is managed by block.c. Drivers are not >allowed to modify this pointer. You declared BlockDriver.instance_size >= sizeof(BackupBlockJob *) but didn't use it. Doh, thanks. > >I guess this should be: > > static void backup_top_enable(BackupBlockJob *job) > { > BackupBlockJob **jobp = job->bs->opaque; > *jobp = job; > } > > static void backup_top_disable(BackupBlockJob *job) > { > BackupBlockJob **jobp = job->bs->opaque; > *jobp = NULL; > } > > ... > > static int coroutine_fn backup_top_co_pwritev(BlockDriverState *bs, > uint64_t offset, > uint64_t bytes, > QEMUIOVector *qiov, int flags) > { > int ret = 0; > BackupBlockJob *job = *(BackupBlockJob **)bs->opaque; > if (job) { > >Alternatively filter->job can be used but that may be a legacy field >that will be removed eventually. > >> + >> static void coroutine_fn backup_run(void *opaque) >> { >> BackupBlockJob *job = opaque; >> @@ -435,13 +456,12 @@ static void coroutine_fn backup_run(void *opaque) >> job->done_bitmap = bitmap_new(DIV_ROUND_UP(job->common.len, >> job->cluster_size)); >> >> - job->before_write.notify = backup_before_write_notify; >> - bdrv_add_before_write_notifier(bs, &job->before_write); >> + backup_top_enable(job); >> >> if (job->sync_mode == MIRROR_SYNC_MODE_NONE) { >> while (!block_job_is_cancelled(&job->common)) { >> - /* Yield until the job is cancelled. We just let our before_write >> - * notify callback service CoW requests. */ >> + /* Yield until the job is cancelled. We just let our backup_top >> + * filter service CoW requests. */ >> block_job_yield(&job->common); >> } >> } else if (job->sync_mode == MIRROR_SYNC_MODE_INCREMENTAL) { >> @@ -507,8 +527,7 @@ static void coroutine_fn backup_run(void *opaque) >> } >> } >> } >> - >> - notifier_with_return_remove(&job->before_write); >> + backup_top_disable(job); >> >> /* wait until pending backup_do_cow() calls have completed */ >> qemu_co_rwlock_wrlock(&job->flush_rwlock); >> @@ -532,6 +551,124 @@ static const BlockJobDriver backup_job_driver = { >> .drain = backup_drain, >> }; >> >> +static int coroutine_fn backup_top_co_preadv(BlockDriverState *bs, >> + uint64_t offset, >> + uint64_t bytes, >> + QEMUIOVector *qiov, int flags) >> +{ >> + return bdrv_co_preadv(bs->file, offset, bytes, qiov, flags); >> +} >> + >> +static int coroutine_fn backup_top_co_pwritev(BlockDriverState *bs, >> + uint64_t offset, >> + uint64_t bytes, >> + QEMUIOVector *qiov, int flags) >> +{ >> + int ret = 0; >> + BackupBlockJob *job = bs->opaque; >> + if (job) { >> + assert(bs == blk_bs(job->common.blk)); >> + assert(QEMU_IS_ALIGNED(offset, BDRV_SECTOR_SIZE)); >> + assert(QEMU_IS_ALIGNED(bytes, BDRV_SECTOR_SIZE)); >> + ret = backup_do_cow(job, offset, bytes, NULL, true); >> + } >> + >> + return ret < 0 ? ret : bdrv_co_pwritev(bs->file, offset, bytes, >> + qiov, flags); >> +} >> + >> +static int coroutine_fn backup_top_co_pwrite_zeroes(BlockDriverState *bs, >> + int64_t offset, >> + int bytes, >> + BdrvRequestFlags flags) >> +{ >> + int ret = 0; >> + BackupBlockJob *job = bs->opaque; >> + if (job) { >> + assert(bs == blk_bs(job->common.blk)); >> + assert(QEMU_IS_ALIGNED(offset, BDRV_SECTOR_SIZE)); >> + assert(QEMU_IS_ALIGNED(bytes, BDRV_SECTOR_SIZE)); >> + ret = backup_do_cow(job, offset, bytes, NULL, true); >> + } >> + >> + return ret < 0 ? ret : bdrv_co_pwrite_zeroes(bs->file, offset, bytes, >> + flags); >> +} >> + >> +static int coroutine_fn backup_top_co_pdiscard(BlockDriverState *bs, >> + int64_t offset, int bytes) >> +{ >> + int ret = 0; >> + BackupBlockJob *job = bs->opaque; >> + if (job) { >> + assert(bs == blk_bs(job->common.blk)); >> + assert(QEMU_IS_ALIGNED(offset, BDRV_SECTOR_SIZE)); >> + assert(QEMU_IS_ALIGNED(bytes, BDRV_SECTOR_SIZE)); >> + ret = backup_do_cow(job, offset, bytes, NULL, true); >> + } >> + >> + return ret < 0 ? ret : bdrv_co_pdiscard(bs->file->bs, offset, bytes); >> +} >> + >> +static int backup_top_co_flush(BlockDriverState *bs) >> +{ >> + return bdrv_co_flush(bs->file->bs); >> +} >> + >> +static int backup_top_open(BlockDriverState *bs, QDict *options, >> + int flags, Error **errp) >> +{ >> + return 0; >> +} >> + >> +static void backup_top_close(BlockDriverState *bs) >> +{ >> +} >> + >> +static int64_t backup_top_getlength(BlockDriverState *bs) >> +{ >> + return bs->file ? bdrv_getlength(bs->file->bs) : 0; >> +} >> + >> +static bool backup_recurse_is_first_non_filter(BlockDriverState *bs, >> + BlockDriverState *candidate) >> +{ >> + return bdrv_recurse_is_first_non_filter(bs->file->bs, candidate); >> +} >> + >> +static int64_t coroutine_fn backup_co_get_block_status(BlockDriverState *bs, >> + int64_t sector_num, >> + int nb_sectors, >> + int *pnum, >> + BlockDriverState **file) >> +{ >> + assert(bs->file && bs->file->bs); >> + *pnum = nb_sectors; >> + *file = bs->file->bs; >> + return BDRV_BLOCK_RAW | BDRV_BLOCK_OFFSET_VALID | >> + (sector_num << BDRV_SECTOR_BITS); >> +} >> +static BlockDriver backup_top = { >> + .format_name = "backup-top", >> + .instance_size = sizeof(BackupBlockJob *), >> + >> + .bdrv_open = backup_top_open, > >.bdrv_open may be NULL. There's no need to define this function. > >> + .bdrv_close = backup_top_close, >> + >> + .bdrv_co_flush = backup_top_co_flush, >> + .bdrv_co_preadv = backup_top_co_preadv, >> + .bdrv_co_pwritev = backup_top_co_pwritev, >> + .bdrv_co_pwrite_zeroes = backup_top_co_pwrite_zeroes, >> + .bdrv_co_pdiscard = backup_top_co_pdiscard, >> + >> + .bdrv_getlength = backup_top_getlength, >> + .bdrv_child_perm = bdrv_filter_default_perms, >> + .bdrv_recurse_is_first_non_filter = backup_recurse_is_first_non_filter, > >I think this is dead code since .is_filter = true. It will not be >called. bdrv_recurse_is_first_non_filter() is only called if is_filter is true and the driver implements it to allow recursion to its children. > >> + .bdrv_co_get_block_status = backup_co_get_block_status, >> + >> + .is_filter = true, >> +}; >> + >> BlockJob *backup_job_create(const char *job_id, BlockDriverState *bs, >> BlockDriverState *target, int64_t speed, >> MirrorSyncMode sync_mode, BdrvDirtyBitmap *sync_bitmap, >> @@ -545,6 +682,7 @@ BlockJob *backup_job_create(const char *job_id, BlockDriverState *bs, >> int64_t len; >> BlockDriverInfo bdi; >> BackupBlockJob *job = NULL; >> + BlockDriverState *filter = NULL; >> int ret; >> >> assert(bs); >> @@ -606,17 +744,33 @@ BlockJob *backup_job_create(const char *job_id, BlockDriverState *bs, >> bdrv_get_device_name(bs)); >> goto error; >> } >> + /* Setup before write filter */ >> + filter = >> + bdrv_new_open_driver(&backup_top, >> + NULL, bdrv_get_flags(bs), NULL, &error_abort); >> + filter->implicit = true; >> + filter->total_sectors = bs->total_sectors; >> + bdrv_set_aio_context(filter, bdrv_get_aio_context(bs)); >> + >> + /* Insert before write notifier in the BDS chain */ >> + bdrv_ref(filter); >> + bdrv_drained_begin(bs); >> + bdrv_append_file(filter, bs, &error_abort); >> + bdrv_drained_end(bs); >> >> /* job->common.len is fixed, so we can't allow resize */ >> - job = block_job_create(job_id, &backup_job_driver, bs, >> + job = block_job_create(job_id, &backup_job_driver, filter, >> BLK_PERM_CONSISTENT_READ, >> BLK_PERM_CONSISTENT_READ | BLK_PERM_WRITE | >> BLK_PERM_WRITE_UNCHANGED | BLK_PERM_GRAPH_MOD, >> speed, creation_flags, cb, opaque, errp); >> + bdrv_unref(filter); >> if (!job) { >> goto error; >> } >> >> + job->filter = filter; > >Is it okay to use filter here after bdrv_unref()? Yes, this is only to make sure it won't get freed if bs doesn't have a parent. It is a ref/unref pair around bdrv_append_file and block_job_create, and filter will have refcnt >= 1 after the unref. I will add a comment for clarification. Thanks for the comments! > >> + >> /* The target must match the source in size, so no resize here either */ >> job->target = blk_new(BLK_PERM_WRITE, >> BLK_PERM_CONSISTENT_READ | BLK_PERM_WRITE | >> @@ -675,6 +829,13 @@ BlockJob *backup_job_create(const char *job_id, BlockDriverState *bs, >> if (job) { >> backup_clean(&job->common); >> block_job_early_fail(&job->common); >> + } else { >> + /* don't leak filter if job creation failed */ >> + if (filter) { >> + bdrv_child_try_set_perm(filter->file, 0, BLK_PERM_ALL, >> + &error_abort); >> + bdrv_replace_node(filter, bs, &error_abort); >> + } >> } >> >> return NULL; >> diff --git a/block/mirror.c b/block/mirror.c >> index e1a160e6ea..3044472fd4 100644 >> --- a/block/mirror.c >> +++ b/block/mirror.c >> @@ -1174,11 +1174,12 @@ static void mirror_start_job(const char *job_id, BlockDriverState *bs, >> mirror_top_bs->total_sectors = bs->total_sectors; >> bdrv_set_aio_context(mirror_top_bs, bdrv_get_aio_context(bs)); >> >> - /* bdrv_append takes ownership of the mirror_top_bs reference, need to keep >> - * it alive until block_job_create() succeeds even if bs has no parent. */ >> + /* bdrv_append_backing() takes ownership of the mirror_top_bs reference, >> + * need to keep it alive until block_job_create() succeeds even if bs has >> + * no parent. */ >> bdrv_ref(mirror_top_bs); >> bdrv_drained_begin(bs); >> - bdrv_append(mirror_top_bs, bs, &local_err); >> + bdrv_append_backing(mirror_top_bs, bs, &local_err); >> bdrv_drained_end(bs); >> >> if (local_err) { >> diff --git a/blockdev.c b/blockdev.c >> index 5c11c245b0..8e2fc6e64c 100644 >> --- a/blockdev.c >> +++ b/blockdev.c >> @@ -1788,7 +1788,7 @@ static void external_snapshot_prepare(BlkActionState *common, >> * can fail, so we need to do it in .prepare; undoing it for abort is >> * always possible. */ >> bdrv_ref(state->new_bs); >> - bdrv_append(state->new_bs, state->old_bs, &local_err); >> + bdrv_append_backing(state->new_bs, state->old_bs, &local_err); >> if (local_err) { >> error_propagate(errp, local_err); >> return; >> diff --git a/include/block/block.h b/include/block/block.h >> index d1f03cb48b..744b50e734 100644 >> --- a/include/block/block.h >> +++ b/include/block/block.h >> @@ -244,8 +244,10 @@ int bdrv_create(BlockDriver *drv, const char* filename, >> QemuOpts *opts, Error **errp); >> int bdrv_create_file(const char *filename, QemuOpts *opts, Error **errp); >> BlockDriverState *bdrv_new(void); >> -void bdrv_append(BlockDriverState *bs_new, BlockDriverState *bs_top, >> - Error **errp); >> +void bdrv_append_file(BlockDriverState *bs_new, BlockDriverState *bs_top, >> + Error **errp); >> +void bdrv_append_backing(BlockDriverState *bs_new, BlockDriverState *bs_top, >> + Error **errp); >> void bdrv_replace_node(BlockDriverState *from, BlockDriverState *to, >> Error **errp); >> >> @@ -256,6 +258,8 @@ BdrvChild *bdrv_open_child(const char *filename, >> BlockDriverState* parent, >> const BdrvChildRole *child_role, >> bool allow_none, Error **errp); >> +void bdrv_set_file(BlockDriverState *bs, BlockDriverState *file_bs, >> + Error **errp); >> void bdrv_set_backing_hd(BlockDriverState *bs, BlockDriverState *backing_hd, >> Error **errp); >> int bdrv_open_backing_file(BlockDriverState *bs, QDict *parent_options, >> diff --git a/tests/qemu-iotests/141.out b/tests/qemu-iotests/141.out >> index 82e763b68d..cc653c317a 100644 >> --- a/tests/qemu-iotests/141.out >> +++ b/tests/qemu-iotests/141.out >> @@ -9,7 +9,7 @@ Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1048576 backing_file=TEST_DIR/m. >> {"return": {}} >> Formatting 'TEST_DIR/o.IMGFMT', fmt=IMGFMT size=1048576 backing_file=TEST_DIR/t.IMGFMT backing_fmt=IMGFMT >> {"return": {}} >> -{"error": {"class": "GenericError", "desc": "Node drv0 is in use"}} >> +{"error": {"class": "GenericError", "desc": "Block device drv0 is in use"}} >> {"return": {}} >> {"timestamp": {"seconds": TIMESTAMP, "microseconds": TIMESTAMP}, "event": "BLOCK_JOB_CANCELLED", "data": {"device": "job0", "len": 1048576, "offset": 0, "speed": 0, "type": "backup"}} >> {"return": {}} >> -- >> 2.11.0 >> >>
On Wed, Aug 16, 2017 at 11:11:44PM +0300, Manos Pitsidianakis wrote: > On Wed, Aug 16, 2017 at 02:25:44PM +0100, Stefan Hajnoczi wrote: > > On Tue, Aug 15, 2017 at 11:18:53AM +0300, Manos Pitsidianakis wrote: > > > @@ -3142,7 +3174,7 @@ static bool should_update_child(BdrvChild *c, BlockDriverState *to) > > > return false; > > > } > > > > > > - if (c->role == &child_backing) { > > > + if (c->role == &child_backing || c->role == &child_file) { > > > /* If @from is a backing file of @to, ignore the child to avoid > > > * creating a loop. We only want to change the pointer of other > > > * parents. */ > > > > This may have unwanted side-effects. I think you're using is so that > > bdrv_set_file() + bdrv_replace_node() does not create a loop in the > > graph. That is okay if there is only one parent with child_file. If > > there are multiple parents with that role then it's not clear to me that > > they should all be skipped. > > I am afraid I don't understand what you're saying. What is the difference > with the child_backing scenario here? In both cases we should update all > from->parents children unless they also happen to be a child of `to`. If > there are multiple parents with child_file, they are not skipped except for > the ones where `to` is the parent. Okay, I'll have to look at this again. Thanks! > > > +static BlockDriver backup_top = { > > > + .format_name = "backup-top", > > > + .instance_size = sizeof(BackupBlockJob *), > > > + > > > + .bdrv_open = backup_top_open, > > > > .bdrv_open may be NULL. There's no need to define this function. > > > > > + .bdrv_close = backup_top_close, > > > + > > > + .bdrv_co_flush = backup_top_co_flush, > > > + .bdrv_co_preadv = backup_top_co_preadv, > > > + .bdrv_co_pwritev = backup_top_co_pwritev, > > > + .bdrv_co_pwrite_zeroes = backup_top_co_pwrite_zeroes, > > > + .bdrv_co_pdiscard = backup_top_co_pdiscard, > > > + > > > + .bdrv_getlength = backup_top_getlength, > > > + .bdrv_child_perm = bdrv_filter_default_perms, > > > + .bdrv_recurse_is_first_non_filter = backup_recurse_is_first_non_filter, > > > > I think this is dead code since .is_filter = true. It will not be > > called. > > bdrv_recurse_is_first_non_filter() is only called if is_filter is true and > the driver implements it to allow recursion to its children. You are right, I misread the code. Stefan
diff --git a/block.c b/block.c index 2de1c29eb3..81bd51b670 100644 --- a/block.c +++ b/block.c @@ -2088,6 +2088,38 @@ static void bdrv_parent_cb_resize(BlockDriverState *bs) } /* + * Sets the file link of a BDS. A new reference is created; callers + * which don't need their own reference any more must call bdrv_unref(). + */ +void bdrv_set_file(BlockDriverState *bs, BlockDriverState *file_bs, + Error **errp) +{ + if (file_bs) { + bdrv_ref(file_bs); + } + + if (bs->file) { + bdrv_unref_child(bs, bs->file); + } + + if (!file_bs) { + bs->file = NULL; + goto out; + } + + bs->file = bdrv_attach_child(bs, file_bs, "file", &child_file, + errp); + if (!bs->file) { + bdrv_unref(file_bs); + } + + bdrv_refresh_filename(bs); + +out: + bdrv_refresh_limits(bs, NULL); +} + +/* * Sets the backing file link of a BDS. A new reference is created; callers * which don't need their own reference any more must call bdrv_unref(). */ @@ -2355,12 +2387,12 @@ static BlockDriverState *bdrv_append_temp_snapshot(BlockDriverState *bs, goto out; } - /* bdrv_append() consumes a strong reference to bs_snapshot + /* bdrv_append_backing() consumes a strong reference to bs_snapshot * (i.e. it will call bdrv_unref() on it) even on error, so in * order to be able to return one, we have to increase * bs_snapshot's refcount here */ bdrv_ref(bs_snapshot); - bdrv_append(bs_snapshot, bs, &local_err); + bdrv_append_backing(bs_snapshot, bs, &local_err); if (local_err) { error_propagate(errp, local_err); bs_snapshot = NULL; @@ -3142,7 +3174,7 @@ static bool should_update_child(BdrvChild *c, BlockDriverState *to) return false; } - if (c->role == &child_backing) { + if (c->role == &child_backing || c->role == &child_file) { /* If @from is a backing file of @to, ignore the child to avoid * creating a loop. We only want to change the pointer of other * parents. */ @@ -3213,6 +3245,45 @@ out: } /* + * Add new bs node at the top of a BDS chain while the chain is + * live, while keeping required fields on the top layer. + * + * This will modify the BlockDriverState fields, and swap contents + * between bs_new and bs_top. Both bs_new and bs_top are modified. + * + * bs_new must not be attached to a BlockBackend. + * + * bdrv_append_file() takes ownership of a bs_new reference and unrefs it + * because that's what the callers commonly need. bs_new will be referenced by + * the old parents of bs_top after bdrv_append_file() returns. If the caller + * needs to keep a reference of its own, it must call bdrv_ref(). + */ +void bdrv_append_file(BlockDriverState *bs_new, BlockDriverState *bs_top, + Error **errp) +{ + Error *local_err = NULL; + + bdrv_ref(bs_top); + bdrv_set_file(bs_new, bs_top, &local_err); + if (local_err) { + error_propagate(errp, local_err); + bdrv_set_file(bs_new, NULL, &error_abort); + goto out; + } + bdrv_replace_node(bs_top, bs_new, &local_err); + if (local_err) { + error_propagate(errp, local_err); + goto out; + } + + /* bs_new is now referenced by its new parents, we don't need the + * additional reference any more. */ +out: + bdrv_unref(bs_top); + bdrv_unref(bs_new); +} + +/* * Add new bs contents at the top of an image chain while the chain is * live, while keeping required fields on the top layer. * @@ -3223,13 +3294,13 @@ out: * * This function does not create any image files. * - * bdrv_append() takes ownership of a bs_new reference and unrefs it because - * that's what the callers commonly need. bs_new will be referenced by the old - * parents of bs_top after bdrv_append() returns. If the caller needs to keep a - * reference of its own, it must call bdrv_ref(). + * bdrv_append_backing() takes ownership of a bs_new reference and unrefs it + * because that's what the callers commonly need. bs_new will be referenced by + * the old parents of bs_top after bdrv_append_backing() returns. If the caller + * needs to keep a reference of its own, it must call bdrv_ref(). */ -void bdrv_append(BlockDriverState *bs_new, BlockDriverState *bs_top, - Error **errp) +void bdrv_append_backing(BlockDriverState *bs_new, BlockDriverState *bs_top, + Error **errp) { Error *local_err = NULL; diff --git a/block/backup.c b/block/backup.c index 504a089150..0828d522b6 100644 --- a/block/backup.c +++ b/block/backup.c @@ -43,7 +43,7 @@ typedef struct BackupBlockJob { unsigned long *done_bitmap; int64_t cluster_size; bool compress; - NotifierWithReturn before_write; + BlockDriverState *filter; QLIST_HEAD(, CowRequest) inflight_reqs; } BackupBlockJob; @@ -174,20 +174,6 @@ out: return ret; } -static int coroutine_fn backup_before_write_notify( - NotifierWithReturn *notifier, - void *opaque) -{ - BackupBlockJob *job = container_of(notifier, BackupBlockJob, before_write); - BdrvTrackedRequest *req = opaque; - - assert(req->bs == blk_bs(job->common.blk)); - assert(QEMU_IS_ALIGNED(req->offset, BDRV_SECTOR_SIZE)); - assert(QEMU_IS_ALIGNED(req->bytes, BDRV_SECTOR_SIZE)); - - return backup_do_cow(job, req->offset, req->bytes, NULL, true); -} - static void backup_set_speed(BlockJob *job, int64_t speed, Error **errp) { BackupBlockJob *s = container_of(job, BackupBlockJob, common); @@ -202,7 +188,8 @@ static void backup_set_speed(BlockJob *job, int64_t speed, Error **errp) static void backup_cleanup_sync_bitmap(BackupBlockJob *job, int ret) { BdrvDirtyBitmap *bm; - BlockDriverState *bs = blk_bs(job->common.blk); + BlockDriverState *bs = child_bs(blk_bs(job->common.blk)); + assert(bs); if (ret < 0 || block_job_is_cancelled(&job->common)) { /* Merge the successor back into the parent, delete nothing. */ @@ -234,9 +221,31 @@ static void backup_abort(BlockJob *job) static void backup_clean(BlockJob *job) { BackupBlockJob *s = container_of(job, BackupBlockJob, common); + BlockDriverState *bs = child_bs(s->filter), + *filter = s->filter; + assert(s->target); blk_unref(s->target); s->target = NULL; + + /* make sure nothing goes away while removing filter */ + bdrv_ref(filter); + bdrv_ref(bs); + bdrv_drained_begin(bs); + + block_job_remove_all_bdrv(job); + bdrv_child_try_set_perm(filter->file, 0, BLK_PERM_ALL, + &error_abort); + bdrv_replace_node(filter, bs, &error_abort); + + blk_remove_bs(job->blk); + blk_set_perm(job->blk, 0, BLK_PERM_ALL, &error_abort); + blk_insert_bs(job->blk, filter, &error_abort); + + bdrv_drained_end(bs); + bdrv_unref(filter); + bdrv_unref(bs); + s->filter = NULL; } static void backup_attached_aio_context(BlockJob *job, AioContext *aio_context) @@ -421,6 +430,18 @@ out: return ret; } +static void backup_top_enable(BackupBlockJob *job) +{ + BlockDriverState *bs = job->filter; + bs->opaque = job; +} + +static void backup_top_disable(BackupBlockJob *job) +{ + BlockDriverState *bs = job->filter; + bs->opaque = NULL; +} + static void coroutine_fn backup_run(void *opaque) { BackupBlockJob *job = opaque; @@ -435,13 +456,12 @@ static void coroutine_fn backup_run(void *opaque) job->done_bitmap = bitmap_new(DIV_ROUND_UP(job->common.len, job->cluster_size)); - job->before_write.notify = backup_before_write_notify; - bdrv_add_before_write_notifier(bs, &job->before_write); + backup_top_enable(job); if (job->sync_mode == MIRROR_SYNC_MODE_NONE) { while (!block_job_is_cancelled(&job->common)) { - /* Yield until the job is cancelled. We just let our before_write - * notify callback service CoW requests. */ + /* Yield until the job is cancelled. We just let our backup_top + * filter service CoW requests. */ block_job_yield(&job->common); } } else if (job->sync_mode == MIRROR_SYNC_MODE_INCREMENTAL) { @@ -507,8 +527,7 @@ static void coroutine_fn backup_run(void *opaque) } } } - - notifier_with_return_remove(&job->before_write); + backup_top_disable(job); /* wait until pending backup_do_cow() calls have completed */ qemu_co_rwlock_wrlock(&job->flush_rwlock); @@ -532,6 +551,124 @@ static const BlockJobDriver backup_job_driver = { .drain = backup_drain, }; +static int coroutine_fn backup_top_co_preadv(BlockDriverState *bs, + uint64_t offset, + uint64_t bytes, + QEMUIOVector *qiov, int flags) +{ + return bdrv_co_preadv(bs->file, offset, bytes, qiov, flags); +} + +static int coroutine_fn backup_top_co_pwritev(BlockDriverState *bs, + uint64_t offset, + uint64_t bytes, + QEMUIOVector *qiov, int flags) +{ + int ret = 0; + BackupBlockJob *job = bs->opaque; + if (job) { + assert(bs == blk_bs(job->common.blk)); + assert(QEMU_IS_ALIGNED(offset, BDRV_SECTOR_SIZE)); + assert(QEMU_IS_ALIGNED(bytes, BDRV_SECTOR_SIZE)); + ret = backup_do_cow(job, offset, bytes, NULL, true); + } + + return ret < 0 ? ret : bdrv_co_pwritev(bs->file, offset, bytes, + qiov, flags); +} + +static int coroutine_fn backup_top_co_pwrite_zeroes(BlockDriverState *bs, + int64_t offset, + int bytes, + BdrvRequestFlags flags) +{ + int ret = 0; + BackupBlockJob *job = bs->opaque; + if (job) { + assert(bs == blk_bs(job->common.blk)); + assert(QEMU_IS_ALIGNED(offset, BDRV_SECTOR_SIZE)); + assert(QEMU_IS_ALIGNED(bytes, BDRV_SECTOR_SIZE)); + ret = backup_do_cow(job, offset, bytes, NULL, true); + } + + return ret < 0 ? ret : bdrv_co_pwrite_zeroes(bs->file, offset, bytes, + flags); +} + +static int coroutine_fn backup_top_co_pdiscard(BlockDriverState *bs, + int64_t offset, int bytes) +{ + int ret = 0; + BackupBlockJob *job = bs->opaque; + if (job) { + assert(bs == blk_bs(job->common.blk)); + assert(QEMU_IS_ALIGNED(offset, BDRV_SECTOR_SIZE)); + assert(QEMU_IS_ALIGNED(bytes, BDRV_SECTOR_SIZE)); + ret = backup_do_cow(job, offset, bytes, NULL, true); + } + + return ret < 0 ? ret : bdrv_co_pdiscard(bs->file->bs, offset, bytes); +} + +static int backup_top_co_flush(BlockDriverState *bs) +{ + return bdrv_co_flush(bs->file->bs); +} + +static int backup_top_open(BlockDriverState *bs, QDict *options, + int flags, Error **errp) +{ + return 0; +} + +static void backup_top_close(BlockDriverState *bs) +{ +} + +static int64_t backup_top_getlength(BlockDriverState *bs) +{ + return bs->file ? bdrv_getlength(bs->file->bs) : 0; +} + +static bool backup_recurse_is_first_non_filter(BlockDriverState *bs, + BlockDriverState *candidate) +{ + return bdrv_recurse_is_first_non_filter(bs->file->bs, candidate); +} + +static int64_t coroutine_fn backup_co_get_block_status(BlockDriverState *bs, + int64_t sector_num, + int nb_sectors, + int *pnum, + BlockDriverState **file) +{ + assert(bs->file && bs->file->bs); + *pnum = nb_sectors; + *file = bs->file->bs; + return BDRV_BLOCK_RAW | BDRV_BLOCK_OFFSET_VALID | + (sector_num << BDRV_SECTOR_BITS); +} +static BlockDriver backup_top = { + .format_name = "backup-top", + .instance_size = sizeof(BackupBlockJob *), + + .bdrv_open = backup_top_open, + .bdrv_close = backup_top_close, + + .bdrv_co_flush = backup_top_co_flush, + .bdrv_co_preadv = backup_top_co_preadv, + .bdrv_co_pwritev = backup_top_co_pwritev, + .bdrv_co_pwrite_zeroes = backup_top_co_pwrite_zeroes, + .bdrv_co_pdiscard = backup_top_co_pdiscard, + + .bdrv_getlength = backup_top_getlength, + .bdrv_child_perm = bdrv_filter_default_perms, + .bdrv_recurse_is_first_non_filter = backup_recurse_is_first_non_filter, + .bdrv_co_get_block_status = backup_co_get_block_status, + + .is_filter = true, +}; + BlockJob *backup_job_create(const char *job_id, BlockDriverState *bs, BlockDriverState *target, int64_t speed, MirrorSyncMode sync_mode, BdrvDirtyBitmap *sync_bitmap, @@ -545,6 +682,7 @@ BlockJob *backup_job_create(const char *job_id, BlockDriverState *bs, int64_t len; BlockDriverInfo bdi; BackupBlockJob *job = NULL; + BlockDriverState *filter = NULL; int ret; assert(bs); @@ -606,17 +744,33 @@ BlockJob *backup_job_create(const char *job_id, BlockDriverState *bs, bdrv_get_device_name(bs)); goto error; } + /* Setup before write filter */ + filter = + bdrv_new_open_driver(&backup_top, + NULL, bdrv_get_flags(bs), NULL, &error_abort); + filter->implicit = true; + filter->total_sectors = bs->total_sectors; + bdrv_set_aio_context(filter, bdrv_get_aio_context(bs)); + + /* Insert before write notifier in the BDS chain */ + bdrv_ref(filter); + bdrv_drained_begin(bs); + bdrv_append_file(filter, bs, &error_abort); + bdrv_drained_end(bs); /* job->common.len is fixed, so we can't allow resize */ - job = block_job_create(job_id, &backup_job_driver, bs, + job = block_job_create(job_id, &backup_job_driver, filter, BLK_PERM_CONSISTENT_READ, BLK_PERM_CONSISTENT_READ | BLK_PERM_WRITE | BLK_PERM_WRITE_UNCHANGED | BLK_PERM_GRAPH_MOD, speed, creation_flags, cb, opaque, errp); + bdrv_unref(filter); if (!job) { goto error; } + job->filter = filter; + /* The target must match the source in size, so no resize here either */ job->target = blk_new(BLK_PERM_WRITE, BLK_PERM_CONSISTENT_READ | BLK_PERM_WRITE | @@ -675,6 +829,13 @@ BlockJob *backup_job_create(const char *job_id, BlockDriverState *bs, if (job) { backup_clean(&job->common); block_job_early_fail(&job->common); + } else { + /* don't leak filter if job creation failed */ + if (filter) { + bdrv_child_try_set_perm(filter->file, 0, BLK_PERM_ALL, + &error_abort); + bdrv_replace_node(filter, bs, &error_abort); + } } return NULL; diff --git a/block/mirror.c b/block/mirror.c index e1a160e6ea..3044472fd4 100644 --- a/block/mirror.c +++ b/block/mirror.c @@ -1174,11 +1174,12 @@ static void mirror_start_job(const char *job_id, BlockDriverState *bs, mirror_top_bs->total_sectors = bs->total_sectors; bdrv_set_aio_context(mirror_top_bs, bdrv_get_aio_context(bs)); - /* bdrv_append takes ownership of the mirror_top_bs reference, need to keep - * it alive until block_job_create() succeeds even if bs has no parent. */ + /* bdrv_append_backing() takes ownership of the mirror_top_bs reference, + * need to keep it alive until block_job_create() succeeds even if bs has + * no parent. */ bdrv_ref(mirror_top_bs); bdrv_drained_begin(bs); - bdrv_append(mirror_top_bs, bs, &local_err); + bdrv_append_backing(mirror_top_bs, bs, &local_err); bdrv_drained_end(bs); if (local_err) { diff --git a/blockdev.c b/blockdev.c index 5c11c245b0..8e2fc6e64c 100644 --- a/blockdev.c +++ b/blockdev.c @@ -1788,7 +1788,7 @@ static void external_snapshot_prepare(BlkActionState *common, * can fail, so we need to do it in .prepare; undoing it for abort is * always possible. */ bdrv_ref(state->new_bs); - bdrv_append(state->new_bs, state->old_bs, &local_err); + bdrv_append_backing(state->new_bs, state->old_bs, &local_err); if (local_err) { error_propagate(errp, local_err); return; diff --git a/include/block/block.h b/include/block/block.h index d1f03cb48b..744b50e734 100644 --- a/include/block/block.h +++ b/include/block/block.h @@ -244,8 +244,10 @@ int bdrv_create(BlockDriver *drv, const char* filename, QemuOpts *opts, Error **errp); int bdrv_create_file(const char *filename, QemuOpts *opts, Error **errp); BlockDriverState *bdrv_new(void); -void bdrv_append(BlockDriverState *bs_new, BlockDriverState *bs_top, - Error **errp); +void bdrv_append_file(BlockDriverState *bs_new, BlockDriverState *bs_top, + Error **errp); +void bdrv_append_backing(BlockDriverState *bs_new, BlockDriverState *bs_top, + Error **errp); void bdrv_replace_node(BlockDriverState *from, BlockDriverState *to, Error **errp); @@ -256,6 +258,8 @@ BdrvChild *bdrv_open_child(const char *filename, BlockDriverState* parent, const BdrvChildRole *child_role, bool allow_none, Error **errp); +void bdrv_set_file(BlockDriverState *bs, BlockDriverState *file_bs, + Error **errp); void bdrv_set_backing_hd(BlockDriverState *bs, BlockDriverState *backing_hd, Error **errp); int bdrv_open_backing_file(BlockDriverState *bs, QDict *parent_options, diff --git a/tests/qemu-iotests/141.out b/tests/qemu-iotests/141.out index 82e763b68d..cc653c317a 100644 --- a/tests/qemu-iotests/141.out +++ b/tests/qemu-iotests/141.out @@ -9,7 +9,7 @@ Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1048576 backing_file=TEST_DIR/m. {"return": {}} Formatting 'TEST_DIR/o.IMGFMT', fmt=IMGFMT size=1048576 backing_file=TEST_DIR/t.IMGFMT backing_fmt=IMGFMT {"return": {}} -{"error": {"class": "GenericError", "desc": "Node drv0 is in use"}} +{"error": {"class": "GenericError", "desc": "Block device drv0 is in use"}} {"return": {}} {"timestamp": {"seconds": TIMESTAMP, "microseconds": TIMESTAMP}, "event": "BLOCK_JOB_CANCELLED", "data": {"device": "job0", "len": 1048576, "offset": 0, "speed": 0, "type": "backup"}} {"return": {}}
block/backup.c currently uses before write notifiers on the targeted node. We can create a filter node instead to intercept write requests for the backup job on the BDS level, instead of the BlockBackend level. This is part of deprecating before write notifiers, which are hard coded into the block layer. Block filter drivers are inserted into the graph only when a feature is needed. This makes the block layer more modular and reuses the block driver abstraction that is already present. Signed-off-by: Manos Pitsidianakis <el13635@mail.ntua.gr> --- block.c | 89 +++++++++++++++++-- block/backup.c | 207 ++++++++++++++++++++++++++++++++++++++++----- block/mirror.c | 7 +- blockdev.c | 2 +- include/block/block.h | 8 +- tests/qemu-iotests/141.out | 2 +- 6 files changed, 276 insertions(+), 39 deletions(-)