/* * Functions related to barrier IO handling */ #include <linux/kernel.h> #include <linux/module.h> #include <linux/bio.h> #include <linux/blkdev.h> #include <linux/gfp.h> #include "blk.h" /** * blk_queue_ordered - does this queue support ordered writes * @q: the request queue * @ordered: one of QUEUE_ORDERED_* * @prepare_flush_fn: rq setup helper for cache flush ordered writes * * Description: * For journalled file systems, doing ordered writes on a commit * block instead of explicitly doing wait_on_buffer (which is bad * for performance) can be a big win. Block drivers supporting this * feature should call this function and indicate so. * **/ int blk_queue_ordered(struct request_queue *q, unsigned ordered, prepare_flush_fn *prepare_flush_fn) { if (!prepare_flush_fn && (ordered & (QUEUE_ORDERED_DO_PREFLUSH | QUEUE_ORDERED_DO_POSTFLUSH))) { printk(KERN_ERR "%s: prepare_flush_fn required\n", __func__); return -EINVAL; } if (ordered != QUEUE_ORDERED_NONE && ordered != QUEUE_ORDERED_DRAIN && ordered != QUEUE_ORDERED_DRAIN_FLUSH && ordered != QUEUE_ORDERED_DRAIN_FUA && ordered != QUEUE_ORDERED_TAG && ordered != QUEUE_ORDERED_TAG_FLUSH && ordered != QUEUE_ORDERED_TAG_FUA) { printk(KERN_ERR "blk_queue_ordered: bad value %d\n", ordered); return -EINVAL; } q->ordered = ordered; q->next_ordered = ordered; q->prepare_flush_fn = prepare_flush_fn; return 0; } EXPORT_SYMBOL(blk_queue_ordered); /* * Cache flushing for ordered writes handling */ unsigned blk_ordered_cur_seq(struct request_queue *q) { if (!q->ordseq) return 0; return 1 << ffz(q->ordseq); } unsigned blk_ordered_req_seq(struct request *rq) { struct request_queue *q = rq->q; BUG_ON(q->ordseq == 0); if (rq == &q->pre_flush_rq) return QUEUE_ORDSEQ_PREFLUSH; if (rq == &q->bar_rq) return QUEUE_ORDSEQ_BAR; if (rq == &q->post_flush_rq) return QUEUE_ORDSEQ_POSTFLUSH; /* * !fs requests don't need to follow barrier ordering. Always * put them at the front. This fixes the following deadlock. * * http://thread.gmane.org/gmane.linux.kernel/537473 */ if (!blk_fs_request(rq)) return QUEUE_ORDSEQ_DRAIN; if ((rq->cmd_flags & REQ_ORDERED_COLOR) == (q->orig_bar_rq->cmd_flags & REQ_ORDERED_COLOR)) return QUEUE_ORDSEQ_DRAIN; else return QUEUE_ORDSEQ_DONE; } bool blk_ordered_complete_seq(struct request_queue *q, unsigned seq, int error) { struct request *rq; if (error && !q->orderr) q->orderr = error; BUG_ON(q->ordseq & seq); q->ordseq |= seq; if (blk_ordered_cur_seq(q) != QUEUE_ORDSEQ_DONE) return false; /* * Okay, sequence complete. */ q->ordseq = 0; rq = q->orig_bar_rq; __blk_end_request_all(rq, q->orderr); return true; } static void pre_flush_end_io(struct request *rq, int error) { elv_completed_request(rq->q, rq); blk_ordered_complete_seq(rq->q, QUEUE_ORDSEQ_PREFLUSH, error); } static void bar_end_io(struct request *rq, int error) { elv_completed_request(rq->q, rq); blk_ordered_complete_seq(rq->q, QUEUE_ORDSEQ_BAR, error); } static void post_flush_end_io(struct request *rq, int error) { elv_completed_request(rq->q, rq); blk_ordered_complete_seq(rq->q, QUEUE_ORDSEQ_POSTFLUSH, error); } static void queue_flush(struct request_queue *q, unsigned which) { struct request *rq; rq_end_io_fn *end_io; if (which == QUEUE_ORDERED_DO_PREFLUSH) { rq = &q->pre_flush_rq; end_io = pre_flush_end_io; } else { rq = &q->post_flush_rq; end_io = post_flush_end_io; } blk_rq_init(q, rq); rq->cmd_flags = REQ_HARDBARRIER; rq->rq_disk = q->bar_rq.rq_disk; rq->end_io = end_io; q->prepare_flush_fn(q, rq); elv_insert(q, rq, ELEVATOR_INSERT_FRONT); } static inline bool start_ordered(struct request_queue *q, struct request **rqp) { struct request *rq = *rqp; unsigned skip = 0; q->orderr = 0; q->ordered = q->next_ordered; q->ordseq |= QUEUE_ORDSEQ_STARTED; /* * For an empty barrier, there's no actual BAR request, which * in turn makes POSTFLUSH unnecessary. Mask them off. */ if (!blk_rq_sectors(rq)) { q->ordered &= ~(QUEUE_ORDERED_DO_BAR | QUEUE_ORDERED_DO_POSTFLUSH); /* * Empty barrier on a write-through device w/ ordered * tag has no command to issue and without any command * to issue, ordering by tag can't be used. Drain * instead. */ if ((q->ordered & QUEUE_ORDERED_BY_TAG) && !(q->ordered & QUEUE_ORDERED_DO_PREFLUSH)) { q->ordered &= ~QUEUE_ORDERED_BY_TAG; q->ordered |= QUEUE_ORDERED_BY_DRAIN; } } /* stash away the original request */ blk_dequeue_request(rq); q->orig_bar_rq = rq; rq = NULL; /* * Queue ordered sequence. As we stack them at the head, we * need to queue in reverse order. Note that we rely on that * no fs request uses ELEVATOR_INSERT_FRONT and thus no fs * request gets inbetween ordered sequence. */ if (q->ordered & QUEUE_ORDERED_DO_POSTFLUSH) { queue_flush(q, QUEUE_ORDERED_DO_POSTFLUSH); rq = &q->post_flush_rq; } else skip |= QUEUE_ORDSEQ_POSTFLUSH; if (q->ordered & QUEUE_ORDERED_DO_BAR) { rq = &q->bar_rq; /* initialize proxy request and queue it */ blk_rq_init(q, rq); if (bio_data_dir(q->orig_bar_rq->bio) == WRITE) rq->cmd_flags |= REQ_RW; if (q->ordered & QUEUE_ORDERED_DO_FUA) rq->cmd_flags |= REQ_FUA; init_request_from_bio(rq, q->orig_bar_rq->bio); rq->end_io = bar_end_io; elv_insert(q, rq, ELEVATOR_INSERT_FRONT); } else skip |= QUEUE_ORDSEQ_BAR; if (q->ordered & QUEUE_ORDERED_DO_PREFLUSH) { queue_flush(q, QUEUE_ORDERED_DO_PREFLUSH); rq = &q->pre_flush_rq; } else skip |= QUEUE_ORDSEQ_PREFLUSH; if ((q->ordered & QUEUE_ORDERED_BY_DRAIN) && queue_in_flight(q)) rq = NULL; else skip |= QUEUE_ORDSEQ_DRAIN; *rqp = rq; /* * Complete skipped sequences. If whole sequence is complete, * return false to tell elevator that this request is gone. */ return !blk_ordered_complete_seq(q, skip, 0); } bool blk_do_ordered(struct request_queue *q, struct request **rqp) { struct request *rq = *rqp; const int is_barrier = blk_fs_request(rq) && blk_barrier_rq(rq); if (!q->ordseq) { if (!is_barrier) return true; if (q->next_ordered != QUEUE_ORDERED_NONE) return start_ordered(q, rqp); else { /* * Queue ordering not supported. Terminate * with prejudice. */ blk_dequeue_request(rq); __blk_end_request_all(rq, -EOPNOTSUPP); *rqp = NULL; return false; } } /* * Ordered sequence in progress */ /* Special requests are not subject to ordering rules. */ if (!blk_fs_request(rq) && rq != &q->pre_flush_rq && rq != &q->post_flush_rq) return true; if (q->ordered & QUEUE_ORDERED_BY_TAG) { /* Ordered by tag. Blocking the next barrier is enough. */ if (is_barrier && rq != &q->bar_rq) *rqp = NULL; } else { /* Ordered by draining. Wait for turn. */ WARN_ON(blk_ordered_req_seq(rq) < blk_ordered_cur_seq(q)); if (blk_ordered_req_seq(rq) > blk_ordered_cur_seq(q)) *rqp = NULL; } return true; } static void bio_end_empty_barrier(struct bio *bio, int err) { if (err) { if (err == -EOPNOTSUPP) set_bit(BIO_EOPNOTSUPP, &bio->bi_flags); clear_bit(BIO_UPTODATE, &bio->bi_flags); } if (bio->bi_private) complete(bio->bi_private); bio_put(bio); } /** * blkdev_issue_flush - queue a flush * @bdev: blockdev to issue flush for * @gfp_mask: memory allocation flags (for bio_alloc) * @error_sector: error sector * @flags: BLKDEV_IFL_* flags to control behaviour * * Description: * Issue a flush for the block device in question. Caller can supply * room for storing the error offset in case of a flush error, if they * wish to. If WAIT flag is not passed then caller may check only what * request was pushed in some internal queue for later handling. */ int blkdev_issue_flush(struct block_device *bdev, gfp_t gfp_mask, sector_t *error_sector, unsigned long flags) { DECLARE_COMPLETION_ONSTACK(wait); struct request_queue *q; struct bio *bio; int ret = 0; if (bdev->bd_disk == NULL) return -ENXIO; q = bdev_get_queue(bdev); if (!q) return -ENXIO; bio = bio_alloc(gfp_mask, 0); bio->bi_end_io = bio_end_empty_barrier; bio->bi_bdev = bdev; if (test_bit(BLKDEV_WAIT, &flags)) bio->bi_private = &wait; bio_get(bio); submit_bio(WRITE_BARRIER, bio); if (test_bit(BLKDEV_WAIT, &flags)) { wait_for_completion(&wait); /* * The driver must store the error location in ->bi_sector, if * it supports it. For non-stacked drivers, this should be * copied from blk_rq_pos(rq). */ if (error_sector) *error_sector = bio->bi_sector; } if (bio_flagged(bio, BIO_EOPNOTSUPP)) ret = -EOPNOTSUPP; else if (!bio_flagged(bio, BIO_UPTODATE)) ret = -EIO; bio_put(bio); return ret; } EXPORT_SYMBOL(blkdev_issue_flush);