/* * Functions related to barrier IO handling */ #include <linux/kernel.h> #include <linux/module.h> #include <linux/bio.h> #include <linux/blkdev.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 (ordered & (QUEUE_ORDERED_PREFLUSH | QUEUE_ORDERED_POSTFLUSH) && prepare_flush_fn == NULL) { printk(KERN_ERR "%s: prepare_flush_fn required\n", __FUNCTION__); 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 */ inline 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; } void 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; /* * Okay, sequence complete. */ q->ordseq = 0; rq = q->orig_bar_rq; if (__blk_end_request(rq, q->orderr, blk_rq_bytes(rq))) BUG(); } 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_PREFLUSH) { rq = &q->pre_flush_rq; end_io = pre_flush_end_io; } else { rq = &q->post_flush_rq; end_io = post_flush_end_io; } rq->cmd_flags = REQ_HARDBARRIER; rq_init(q, rq); rq->elevator_private = NULL; rq->elevator_private2 = NULL; 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 struct request *start_ordered(struct request_queue *q, struct request *rq) { q->orderr = 0; q->ordered = q->next_ordered; q->ordseq |= QUEUE_ORDSEQ_STARTED; /* * Prep proxy barrier request. */ blkdev_dequeue_request(rq); q->orig_bar_rq = rq; rq = &q->bar_rq; rq->cmd_flags = 0; rq_init(q, rq); if (bio_data_dir(q->orig_bar_rq->bio) == WRITE) rq->cmd_flags |= REQ_RW; if (q->ordered & QUEUE_ORDERED_FUA) rq->cmd_flags |= REQ_FUA; rq->elevator_private = NULL; rq->elevator_private2 = NULL; init_request_from_bio(rq, q->orig_bar_rq->bio); rq->end_io = bar_end_io; /* * 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 this request is * an empty barrier, we don't need to do a postflush ever since * there will be no data written between the pre and post flush. * Hence a single flush will suffice. */ if ((q->ordered & QUEUE_ORDERED_POSTFLUSH) && !blk_empty_barrier(rq)) queue_flush(q, QUEUE_ORDERED_POSTFLUSH); else q->ordseq |= QUEUE_ORDSEQ_POSTFLUSH; elv_insert(q, rq, ELEVATOR_INSERT_FRONT); if (q->ordered & QUEUE_ORDERED_PREFLUSH) { queue_flush(q, QUEUE_ORDERED_PREFLUSH); rq = &q->pre_flush_rq; } else q->ordseq |= QUEUE_ORDSEQ_PREFLUSH; if ((q->ordered & QUEUE_ORDERED_TAG) || q->in_flight == 0) q->ordseq |= QUEUE_ORDSEQ_DRAIN; else rq = NULL; return rq; } int 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 1; if (q->next_ordered != QUEUE_ORDERED_NONE) { *rqp = start_ordered(q, rq); return 1; } else { /* * This can happen when the queue switches to * ORDERED_NONE while this request is on it. */ blkdev_dequeue_request(rq); if (__blk_end_request(rq, -EOPNOTSUPP, blk_rq_bytes(rq))) BUG(); *rqp = NULL; return 0; } } /* * 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 1; if (q->ordered & QUEUE_ORDERED_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 1; } static void bio_end_empty_barrier(struct bio *bio, int err) { if (err) clear_bit(BIO_UPTODATE, &bio->bi_flags); complete(bio->bi_private); } /** * blkdev_issue_flush - queue a flush * @bdev: blockdev to issue flush for * @error_sector: error sector * * 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. Caller must run wait_for_completion() on its own. */ int blkdev_issue_flush(struct block_device *bdev, sector_t *error_sector) { DECLARE_COMPLETION_ONSTACK(wait); struct request_queue *q; struct bio *bio; int ret; if (bdev->bd_disk == NULL) return -ENXIO; q = bdev_get_queue(bdev); if (!q) return -ENXIO; bio = bio_alloc(GFP_KERNEL, 0); if (!bio) return -ENOMEM; bio->bi_end_io = bio_end_empty_barrier; bio->bi_private = &wait; bio->bi_bdev = bdev; submit_bio(1 << BIO_RW_BARRIER, bio); 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 rq->sector. */ if (error_sector) *error_sector = bio->bi_sector; ret = 0; if (!bio_flagged(bio, BIO_UPTODATE)) ret = -EIO; bio_put(bio); return ret; } EXPORT_SYMBOL(blkdev_issue_flush);