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author | Linus Torvalds <torvalds@linux-foundation.org> | 2010-10-22 17:07:18 -0700 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2010-10-22 17:07:18 -0700 |
commit | a2887097f25cd38cadfc11d10769e2b349fb5eca (patch) | |
tree | cd4adcb305365d6ba9acd2c02d4eb9d0125c6f8d /drivers/md/dm.c | |
parent | 8abfc6e7a45eb74e51904bbae676fae008b11366 (diff) | |
parent | 005a1d15f5a6b2bb4ada80349513effbf22b4588 (diff) | |
download | linux-3.10-a2887097f25cd38cadfc11d10769e2b349fb5eca.tar.gz linux-3.10-a2887097f25cd38cadfc11d10769e2b349fb5eca.tar.bz2 linux-3.10-a2887097f25cd38cadfc11d10769e2b349fb5eca.zip |
Merge branch 'for-2.6.37/barrier' of git://git.kernel.dk/linux-2.6-block
* 'for-2.6.37/barrier' of git://git.kernel.dk/linux-2.6-block: (46 commits)
xen-blkfront: disable barrier/flush write support
Added blk-lib.c and blk-barrier.c was renamed to blk-flush.c
block: remove BLKDEV_IFL_WAIT
aic7xxx_old: removed unused 'req' variable
block: remove the BH_Eopnotsupp flag
block: remove the BLKDEV_IFL_BARRIER flag
block: remove the WRITE_BARRIER flag
swap: do not send discards as barriers
fat: do not send discards as barriers
ext4: do not send discards as barriers
jbd2: replace barriers with explicit flush / FUA usage
jbd2: Modify ASYNC_COMMIT code to not rely on queue draining on barrier
jbd: replace barriers with explicit flush / FUA usage
nilfs2: replace barriers with explicit flush / FUA usage
reiserfs: replace barriers with explicit flush / FUA usage
gfs2: replace barriers with explicit flush / FUA usage
btrfs: replace barriers with explicit flush / FUA usage
xfs: replace barriers with explicit flush / FUA usage
block: pass gfp_mask and flags to sb_issue_discard
dm: convey that all flushes are processed as empty
...
Diffstat (limited to 'drivers/md/dm.c')
-rw-r--r-- | drivers/md/dm.c | 398 |
1 files changed, 81 insertions, 317 deletions
diff --git a/drivers/md/dm.c b/drivers/md/dm.c index 7967eca5a2d..7cb1352f7e7 100644 --- a/drivers/md/dm.c +++ b/drivers/md/dm.c @@ -110,7 +110,6 @@ EXPORT_SYMBOL_GPL(dm_get_rq_mapinfo); #define DMF_FREEING 3 #define DMF_DELETING 4 #define DMF_NOFLUSH_SUSPENDING 5 -#define DMF_QUEUE_IO_TO_THREAD 6 /* * Work processed by per-device workqueue. @@ -144,24 +143,9 @@ struct mapped_device { spinlock_t deferred_lock; /* - * An error from the barrier request currently being processed. - */ - int barrier_error; - - /* - * Protect barrier_error from concurrent endio processing - * in request-based dm. - */ - spinlock_t barrier_error_lock; - - /* - * Processing queue (flush/barriers) + * Processing queue (flush) */ struct workqueue_struct *wq; - struct work_struct barrier_work; - - /* A pointer to the currently processing pre/post flush request */ - struct request *flush_request; /* * The current mapping. @@ -200,8 +184,8 @@ struct mapped_device { /* sysfs handle */ struct kobject kobj; - /* zero-length barrier that will be cloned and submitted to targets */ - struct bio barrier_bio; + /* zero-length flush that will be cloned and submitted to targets */ + struct bio flush_bio; }; /* @@ -512,7 +496,7 @@ static void end_io_acct(struct dm_io *io) /* * After this is decremented the bio must not be touched if it is - * a barrier. + * a flush. */ dm_disk(md)->part0.in_flight[rw] = pending = atomic_dec_return(&md->pending[rw]); @@ -528,16 +512,12 @@ static void end_io_acct(struct dm_io *io) */ static void queue_io(struct mapped_device *md, struct bio *bio) { - down_write(&md->io_lock); + unsigned long flags; - spin_lock_irq(&md->deferred_lock); + spin_lock_irqsave(&md->deferred_lock, flags); bio_list_add(&md->deferred, bio); - spin_unlock_irq(&md->deferred_lock); - - if (!test_and_set_bit(DMF_QUEUE_IO_TO_THREAD, &md->flags)) - queue_work(md->wq, &md->work); - - up_write(&md->io_lock); + spin_unlock_irqrestore(&md->deferred_lock, flags); + queue_work(md->wq, &md->work); } /* @@ -625,11 +605,9 @@ static void dec_pending(struct dm_io *io, int error) * Target requested pushing back the I/O. */ spin_lock_irqsave(&md->deferred_lock, flags); - if (__noflush_suspending(md)) { - if (!(io->bio->bi_rw & REQ_HARDBARRIER)) - bio_list_add_head(&md->deferred, - io->bio); - } else + if (__noflush_suspending(md)) + bio_list_add_head(&md->deferred, io->bio); + else /* noflush suspend was interrupted. */ io->error = -EIO; spin_unlock_irqrestore(&md->deferred_lock, flags); @@ -637,32 +615,23 @@ static void dec_pending(struct dm_io *io, int error) io_error = io->error; bio = io->bio; + end_io_acct(io); + free_io(md, io); + + if (io_error == DM_ENDIO_REQUEUE) + return; - if (bio->bi_rw & REQ_HARDBARRIER) { + if ((bio->bi_rw & REQ_FLUSH) && bio->bi_size) { /* - * There can be just one barrier request so we use - * a per-device variable for error reporting. - * Note that you can't touch the bio after end_io_acct - * - * We ignore -EOPNOTSUPP for empty flush reported by - * underlying devices. We assume that if the device - * doesn't support empty barriers, it doesn't need - * cache flushing commands. + * Preflush done for flush with data, reissue + * without REQ_FLUSH. */ - if (!md->barrier_error && - !(bio_empty_barrier(bio) && io_error == -EOPNOTSUPP)) - md->barrier_error = io_error; - end_io_acct(io); - free_io(md, io); + bio->bi_rw &= ~REQ_FLUSH; + queue_io(md, bio); } else { - end_io_acct(io); - free_io(md, io); - - if (io_error != DM_ENDIO_REQUEUE) { - trace_block_bio_complete(md->queue, bio); - - bio_endio(bio, io_error); - } + /* done with normal IO or empty flush */ + trace_block_bio_complete(md->queue, bio); + bio_endio(bio, io_error); } } } @@ -755,23 +724,6 @@ static void end_clone_bio(struct bio *clone, int error) blk_update_request(tio->orig, 0, nr_bytes); } -static void store_barrier_error(struct mapped_device *md, int error) -{ - unsigned long flags; - - spin_lock_irqsave(&md->barrier_error_lock, flags); - /* - * Basically, the first error is taken, but: - * -EOPNOTSUPP supersedes any I/O error. - * Requeue request supersedes any I/O error but -EOPNOTSUPP. - */ - if (!md->barrier_error || error == -EOPNOTSUPP || - (md->barrier_error != -EOPNOTSUPP && - error == DM_ENDIO_REQUEUE)) - md->barrier_error = error; - spin_unlock_irqrestore(&md->barrier_error_lock, flags); -} - /* * Don't touch any member of the md after calling this function because * the md may be freed in dm_put() at the end of this function. @@ -809,13 +761,11 @@ static void free_rq_clone(struct request *clone) static void dm_end_request(struct request *clone, int error) { int rw = rq_data_dir(clone); - int run_queue = 1; - bool is_barrier = clone->cmd_flags & REQ_HARDBARRIER; struct dm_rq_target_io *tio = clone->end_io_data; struct mapped_device *md = tio->md; struct request *rq = tio->orig; - if (rq->cmd_type == REQ_TYPE_BLOCK_PC && !is_barrier) { + if (rq->cmd_type == REQ_TYPE_BLOCK_PC) { rq->errors = clone->errors; rq->resid_len = clone->resid_len; @@ -829,15 +779,8 @@ static void dm_end_request(struct request *clone, int error) } free_rq_clone(clone); - - if (unlikely(is_barrier)) { - if (unlikely(error)) - store_barrier_error(md, error); - run_queue = 0; - } else - blk_end_request_all(rq, error); - - rq_completed(md, rw, run_queue); + blk_end_request_all(rq, error); + rq_completed(md, rw, true); } static void dm_unprep_request(struct request *rq) @@ -862,16 +805,6 @@ void dm_requeue_unmapped_request(struct request *clone) struct request_queue *q = rq->q; unsigned long flags; - if (unlikely(clone->cmd_flags & REQ_HARDBARRIER)) { - /* - * Barrier clones share an original request. - * Leave it to dm_end_request(), which handles this special - * case. - */ - dm_end_request(clone, DM_ENDIO_REQUEUE); - return; - } - dm_unprep_request(rq); spin_lock_irqsave(q->queue_lock, flags); @@ -961,19 +894,6 @@ static void dm_complete_request(struct request *clone, int error) struct dm_rq_target_io *tio = clone->end_io_data; struct request *rq = tio->orig; - if (unlikely(clone->cmd_flags & REQ_HARDBARRIER)) { - /* - * Barrier clones share an original request. So can't use - * softirq_done with the original. - * Pass the clone to dm_done() directly in this special case. - * It is safe (even if clone->q->queue_lock is held here) - * because there is no I/O dispatching during the completion - * of barrier clone. - */ - dm_done(clone, error, true); - return; - } - tio->error = error; rq->completion_data = clone; blk_complete_request(rq); @@ -990,17 +910,6 @@ void dm_kill_unmapped_request(struct request *clone, int error) struct dm_rq_target_io *tio = clone->end_io_data; struct request *rq = tio->orig; - if (unlikely(clone->cmd_flags & REQ_HARDBARRIER)) { - /* - * Barrier clones share an original request. - * Leave it to dm_end_request(), which handles this special - * case. - */ - BUG_ON(error > 0); - dm_end_request(clone, error); - return; - } - rq->cmd_flags |= REQ_FAILED; dm_complete_request(clone, error); } @@ -1119,7 +1028,7 @@ static void dm_bio_destructor(struct bio *bio) } /* - * Creates a little bio that is just does part of a bvec. + * Creates a little bio that just does part of a bvec. */ static struct bio *split_bvec(struct bio *bio, sector_t sector, unsigned short idx, unsigned int offset, @@ -1134,7 +1043,7 @@ static struct bio *split_bvec(struct bio *bio, sector_t sector, clone->bi_sector = sector; clone->bi_bdev = bio->bi_bdev; - clone->bi_rw = bio->bi_rw & ~REQ_HARDBARRIER; + clone->bi_rw = bio->bi_rw; clone->bi_vcnt = 1; clone->bi_size = to_bytes(len); clone->bi_io_vec->bv_offset = offset; @@ -1161,7 +1070,6 @@ static struct bio *clone_bio(struct bio *bio, sector_t sector, clone = bio_alloc_bioset(GFP_NOIO, bio->bi_max_vecs, bs); __bio_clone(clone, bio); - clone->bi_rw &= ~REQ_HARDBARRIER; clone->bi_destructor = dm_bio_destructor; clone->bi_sector = sector; clone->bi_idx = idx; @@ -1225,16 +1133,15 @@ static void __issue_target_requests(struct clone_info *ci, struct dm_target *ti, __issue_target_request(ci, ti, request_nr, len); } -static int __clone_and_map_empty_barrier(struct clone_info *ci) +static int __clone_and_map_empty_flush(struct clone_info *ci) { unsigned target_nr = 0; struct dm_target *ti; + BUG_ON(bio_has_data(ci->bio)); while ((ti = dm_table_get_target(ci->map, target_nr++))) __issue_target_requests(ci, ti, ti->num_flush_requests, 0); - ci->sector_count = 0; - return 0; } @@ -1289,9 +1196,6 @@ static int __clone_and_map(struct clone_info *ci) sector_t len = 0, max; struct dm_target_io *tio; - if (unlikely(bio_empty_barrier(bio))) - return __clone_and_map_empty_barrier(ci); - if (unlikely(bio->bi_rw & REQ_DISCARD)) return __clone_and_map_discard(ci); @@ -1383,16 +1287,11 @@ static void __split_and_process_bio(struct mapped_device *md, struct bio *bio) ci.map = dm_get_live_table(md); if (unlikely(!ci.map)) { - if (!(bio->bi_rw & REQ_HARDBARRIER)) - bio_io_error(bio); - else - if (!md->barrier_error) - md->barrier_error = -EIO; + bio_io_error(bio); return; } ci.md = md; - ci.bio = bio; ci.io = alloc_io(md); ci.io->error = 0; atomic_set(&ci.io->io_count, 1); @@ -1400,14 +1299,20 @@ static void __split_and_process_bio(struct mapped_device *md, struct bio *bio) ci.io->md = md; spin_lock_init(&ci.io->endio_lock); ci.sector = bio->bi_sector; - ci.sector_count = bio_sectors(bio); - if (unlikely(bio_empty_barrier(bio))) - ci.sector_count = 1; ci.idx = bio->bi_idx; start_io_acct(ci.io); - while (ci.sector_count && !error) - error = __clone_and_map(&ci); + if (bio->bi_rw & REQ_FLUSH) { + ci.bio = &ci.md->flush_bio; + ci.sector_count = 0; + error = __clone_and_map_empty_flush(&ci); + /* dec_pending submits any data associated with flush */ + } else { + ci.bio = bio; + ci.sector_count = bio_sectors(bio); + while (ci.sector_count && !error) + error = __clone_and_map(&ci); + } /* drop the extra reference count */ dec_pending(ci.io, error); @@ -1491,22 +1396,14 @@ static int _dm_request(struct request_queue *q, struct bio *bio) part_stat_add(cpu, &dm_disk(md)->part0, sectors[rw], bio_sectors(bio)); part_stat_unlock(); - /* - * If we're suspended or the thread is processing barriers - * we have to queue this io for later. - */ - if (unlikely(test_bit(DMF_QUEUE_IO_TO_THREAD, &md->flags)) || - unlikely(bio->bi_rw & REQ_HARDBARRIER)) { + /* if we're suspended, we have to queue this io for later */ + if (unlikely(test_bit(DMF_BLOCK_IO_FOR_SUSPEND, &md->flags))) { up_read(&md->io_lock); - if (unlikely(test_bit(DMF_BLOCK_IO_FOR_SUSPEND, &md->flags)) && - bio_rw(bio) == READA) { + if (bio_rw(bio) != READA) + queue_io(md, bio); + else bio_io_error(bio); - return 0; - } - - queue_io(md, bio); - return 0; } @@ -1537,14 +1434,6 @@ static int dm_request(struct request_queue *q, struct bio *bio) return _dm_request(q, bio); } -static bool dm_rq_is_flush_request(struct request *rq) -{ - if (rq->cmd_flags & REQ_FLUSH) - return true; - else - return false; -} - void dm_dispatch_request(struct request *rq) { int r; @@ -1592,22 +1481,15 @@ static int setup_clone(struct request *clone, struct request *rq, { int r; - if (dm_rq_is_flush_request(rq)) { - blk_rq_init(NULL, clone); - clone->cmd_type = REQ_TYPE_FS; - clone->cmd_flags |= (REQ_HARDBARRIER | WRITE); - } else { - r = blk_rq_prep_clone(clone, rq, tio->md->bs, GFP_ATOMIC, - dm_rq_bio_constructor, tio); - if (r) - return r; - - clone->cmd = rq->cmd; - clone->cmd_len = rq->cmd_len; - clone->sense = rq->sense; - clone->buffer = rq->buffer; - } + r = blk_rq_prep_clone(clone, rq, tio->md->bs, GFP_ATOMIC, + dm_rq_bio_constructor, tio); + if (r) + return r; + clone->cmd = rq->cmd; + clone->cmd_len = rq->cmd_len; + clone->sense = rq->sense; + clone->buffer = rq->buffer; clone->end_io = end_clone_request; clone->end_io_data = tio; @@ -1648,9 +1530,6 @@ static int dm_prep_fn(struct request_queue *q, struct request *rq) struct mapped_device *md = q->queuedata; struct request *clone; - if (unlikely(dm_rq_is_flush_request(rq))) - return BLKPREP_OK; - if (unlikely(rq->special)) { DMWARN("Already has something in rq->special."); return BLKPREP_KILL; @@ -1727,6 +1606,7 @@ static void dm_request_fn(struct request_queue *q) struct dm_table *map = dm_get_live_table(md); struct dm_target *ti; struct request *rq, *clone; + sector_t pos; /* * For suspend, check blk_queue_stopped() and increment @@ -1739,15 +1619,14 @@ static void dm_request_fn(struct request_queue *q) if (!rq) goto plug_and_out; - if (unlikely(dm_rq_is_flush_request(rq))) { - BUG_ON(md->flush_request); - md->flush_request = rq; - blk_start_request(rq); - queue_work(md->wq, &md->barrier_work); - goto out; - } + /* always use block 0 to find the target for flushes for now */ + pos = 0; + if (!(rq->cmd_flags & REQ_FLUSH)) + pos = blk_rq_pos(rq); + + ti = dm_table_find_target(map, pos); + BUG_ON(!dm_target_is_valid(ti)); - ti = dm_table_find_target(map, blk_rq_pos(rq)); if (ti->type->busy && ti->type->busy(ti)) goto plug_and_out; @@ -1918,7 +1797,6 @@ out: static const struct block_device_operations dm_blk_dops; static void dm_wq_work(struct work_struct *work); -static void dm_rq_barrier_work(struct work_struct *work); static void dm_init_md_queue(struct mapped_device *md) { @@ -1940,6 +1818,7 @@ static void dm_init_md_queue(struct mapped_device *md) blk_queue_bounce_limit(md->queue, BLK_BOUNCE_ANY); md->queue->unplug_fn = dm_unplug_all; blk_queue_merge_bvec(md->queue, dm_merge_bvec); + blk_queue_flush(md->queue, REQ_FLUSH | REQ_FUA); } /* @@ -1972,7 +1851,6 @@ static struct mapped_device *alloc_dev(int minor) mutex_init(&md->suspend_lock); mutex_init(&md->type_lock); spin_lock_init(&md->deferred_lock); - spin_lock_init(&md->barrier_error_lock); rwlock_init(&md->map_lock); atomic_set(&md->holders, 1); atomic_set(&md->open_count, 0); @@ -1995,7 +1873,6 @@ static struct mapped_device *alloc_dev(int minor) atomic_set(&md->pending[1], 0); init_waitqueue_head(&md->wait); INIT_WORK(&md->work, dm_wq_work); - INIT_WORK(&md->barrier_work, dm_rq_barrier_work); init_waitqueue_head(&md->eventq); md->disk->major = _major; @@ -2015,6 +1892,10 @@ static struct mapped_device *alloc_dev(int minor) if (!md->bdev) goto bad_bdev; + bio_init(&md->flush_bio); + md->flush_bio.bi_bdev = md->bdev; + md->flush_bio.bi_rw = WRITE_FLUSH; + /* Populate the mapping, nobody knows we exist yet */ spin_lock(&_minor_lock); old_md = idr_replace(&_minor_idr, md, minor); @@ -2245,7 +2126,6 @@ static int dm_init_request_based_queue(struct mapped_device *md) blk_queue_softirq_done(md->queue, dm_softirq_done); blk_queue_prep_rq(md->queue, dm_prep_fn); blk_queue_lld_busy(md->queue, dm_lld_busy); - blk_queue_ordered(md->queue, QUEUE_ORDERED_DRAIN_FLUSH); elv_register_queue(md->queue); @@ -2406,43 +2286,6 @@ static int dm_wait_for_completion(struct mapped_device *md, int interruptible) return r; } -static void dm_flush(struct mapped_device *md) -{ - dm_wait_for_completion(md, TASK_UNINTERRUPTIBLE); - - bio_init(&md->barrier_bio); - md->barrier_bio.bi_bdev = md->bdev; - md->barrier_bio.bi_rw = WRITE_BARRIER; - __split_and_process_bio(md, &md->barrier_bio); - - dm_wait_for_completion(md, TASK_UNINTERRUPTIBLE); -} - -static void process_barrier(struct mapped_device *md, struct bio *bio) -{ - md->barrier_error = 0; - - dm_flush(md); - - if (!bio_empty_barrier(bio)) { - __split_and_process_bio(md, bio); - /* - * If the request isn't supported, don't waste time with - * the second flush. - */ - if (md->barrier_error != -EOPNOTSUPP) - dm_flush(md); - } - - if (md->barrier_error != DM_ENDIO_REQUEUE) - bio_endio(bio, md->barrier_error); - else { - spin_lock_irq(&md->deferred_lock); - bio_list_add_head(&md->deferred, bio); - spin_unlock_irq(&md->deferred_lock); - } -} - /* * Process the deferred bios */ @@ -2452,33 +2295,27 @@ static void dm_wq_work(struct work_struct *work) work); struct bio *c; - down_write(&md->io_lock); + down_read(&md->io_lock); while (!test_bit(DMF_BLOCK_IO_FOR_SUSPEND, &md->flags)) { spin_lock_irq(&md->deferred_lock); c = bio_list_pop(&md->deferred); spin_unlock_irq(&md->deferred_lock); - if (!c) { - clear_bit(DMF_QUEUE_IO_TO_THREAD, &md->flags); + if (!c) break; - } - up_write(&md->io_lock); + up_read(&md->io_lock); if (dm_request_based(md)) generic_make_request(c); - else { - if (c->bi_rw & REQ_HARDBARRIER) - process_barrier(md, c); - else - __split_and_process_bio(md, c); - } + else + __split_and_process_bio(md, c); - down_write(&md->io_lock); + down_read(&md->io_lock); } - up_write(&md->io_lock); + up_read(&md->io_lock); } static void dm_queue_flush(struct mapped_device *md) @@ -2488,73 +2325,6 @@ static void dm_queue_flush(struct mapped_device *md) queue_work(md->wq, &md->work); } -static void dm_rq_set_target_request_nr(struct request *clone, unsigned request_nr) -{ - struct dm_rq_target_io *tio = clone->end_io_data; - - tio->info.target_request_nr = request_nr; -} - -/* Issue barrier requests to targets and wait for their completion. */ -static int dm_rq_barrier(struct mapped_device *md) -{ - int i, j; - struct dm_table *map = dm_get_live_table(md); - unsigned num_targets = dm_table_get_num_targets(map); - struct dm_target *ti; - struct request *clone; - - md->barrier_error = 0; - - for (i = 0; i < num_targets; i++) { - ti = dm_table_get_target(map, i); - for (j = 0; j < ti->num_flush_requests; j++) { - clone = clone_rq(md->flush_request, md, GFP_NOIO); - dm_rq_set_target_request_nr(clone, j); - atomic_inc(&md->pending[rq_data_dir(clone)]); - map_request(ti, clone, md); - } - } - - dm_wait_for_completion(md, TASK_UNINTERRUPTIBLE); - dm_table_put(map); - - return md->barrier_error; -} - -static void dm_rq_barrier_work(struct work_struct *work) -{ - int error; - struct mapped_device *md = container_of(work, struct mapped_device, - barrier_work); - struct request_queue *q = md->queue; - struct request *rq; - unsigned long flags; - - /* - * Hold the md reference here and leave it at the last part so that - * the md can't be deleted by device opener when the barrier request - * completes. - */ - dm_get(md); - - error = dm_rq_barrier(md); - - rq = md->flush_request; - md->flush_request = NULL; - - if (error == DM_ENDIO_REQUEUE) { - spin_lock_irqsave(q->queue_lock, flags); - blk_requeue_request(q, rq); - spin_unlock_irqrestore(q->queue_lock, flags); - } else - blk_end_request_all(rq, error); - - blk_run_queue(q); - - dm_put(md); -} - /* * Swap in a new table, returning the old one for the caller to destroy. */ @@ -2677,23 +2447,17 @@ int dm_suspend(struct mapped_device *md, unsigned suspend_flags) * * To get all processes out of __split_and_process_bio in dm_request, * we take the write lock. To prevent any process from reentering - * __split_and_process_bio from dm_request, we set - * DMF_QUEUE_IO_TO_THREAD. - * - * To quiesce the thread (dm_wq_work), we set DMF_BLOCK_IO_FOR_SUSPEND - * and call flush_workqueue(md->wq). flush_workqueue will wait until - * dm_wq_work exits and DMF_BLOCK_IO_FOR_SUSPEND will prevent any - * further calls to __split_and_process_bio from dm_wq_work. + * __split_and_process_bio from dm_request and quiesce the thread + * (dm_wq_work), we set BMF_BLOCK_IO_FOR_SUSPEND and call + * flush_workqueue(md->wq). */ down_write(&md->io_lock); set_bit(DMF_BLOCK_IO_FOR_SUSPEND, &md->flags); - set_bit(DMF_QUEUE_IO_TO_THREAD, &md->flags); up_write(&md->io_lock); /* - * Request-based dm uses md->wq for barrier (dm_rq_barrier_work) which - * can be kicked until md->queue is stopped. So stop md->queue before - * flushing md->wq. + * Stop md->queue before flushing md->wq in case request-based + * dm defers requests to md->wq from md->queue. */ if (dm_request_based(md)) stop_queue(md->queue); |