| /* |
| * Functions to sequence FLUSH and FUA writes. |
| * |
| * Copyright (C) 2011 Max Planck Institute for Gravitational Physics |
| * Copyright (C) 2011 Tejun Heo <tj@kernel.org> |
| * |
| * This file is released under the GPLv2. |
| * |
| * REQ_{FLUSH|FUA} requests are decomposed to sequences consisted of three |
| * optional steps - PREFLUSH, DATA and POSTFLUSH - according to the request |
| * properties and hardware capability. |
| * |
| * If a request doesn't have data, only REQ_FLUSH makes sense, which |
| * indicates a simple flush request. If there is data, REQ_FLUSH indicates |
| * that the device cache should be flushed before the data is executed, and |
| * REQ_FUA means that the data must be on non-volatile media on request |
| * completion. |
| * |
| * If the device doesn't have writeback cache, FLUSH and FUA don't make any |
| * difference. The requests are either completed immediately if there's no |
| * data or executed as normal requests otherwise. |
| * |
| * If the device has writeback cache and supports FUA, REQ_FLUSH is |
| * translated to PREFLUSH but REQ_FUA is passed down directly with DATA. |
| * |
| * If the device has writeback cache and doesn't support FUA, REQ_FLUSH is |
| * translated to PREFLUSH and REQ_FUA to POSTFLUSH. |
| * |
| * The actual execution of flush is double buffered. Whenever a request |
| * needs to execute PRE or POSTFLUSH, it queues at |
| * fq->flush_queue[fq->flush_pending_idx]. Once certain criteria are met, a |
| * REQ_OP_FLUSH is issued and the pending_idx is toggled. When the flush |
| * completes, all the requests which were pending are proceeded to the next |
| * step. This allows arbitrary merging of different types of FLUSH/FUA |
| * requests. |
| * |
| * Currently, the following conditions are used to determine when to issue |
| * flush. |
| * |
| * C1. At any given time, only one flush shall be in progress. This makes |
| * double buffering sufficient. |
| * |
| * C2. Flush is deferred if any request is executing DATA of its sequence. |
| * This avoids issuing separate POSTFLUSHes for requests which shared |
| * PREFLUSH. |
| * |
| * C3. The second condition is ignored if there is a request which has |
| * waited longer than FLUSH_PENDING_TIMEOUT. This is to avoid |
| * starvation in the unlikely case where there are continuous stream of |
| * FUA (without FLUSH) requests. |
| * |
| * For devices which support FUA, it isn't clear whether C2 (and thus C3) |
| * is beneficial. |
| * |
| * Note that a sequenced FLUSH/FUA request with DATA is completed twice. |
| * Once while executing DATA and again after the whole sequence is |
| * complete. The first completion updates the contained bio but doesn't |
| * finish it so that the bio submitter is notified only after the whole |
| * sequence is complete. This is implemented by testing REQ_FLUSH_SEQ in |
| * req_bio_endio(). |
| * |
| * The above peculiarity requires that each FLUSH/FUA request has only one |
| * bio attached to it, which is guaranteed as they aren't allowed to be |
| * merged in the usual way. |
| */ |
| |
| #include <linux/kernel.h> |
| #include <linux/module.h> |
| #include <linux/bio.h> |
| #include <linux/blkdev.h> |
| #include <linux/gfp.h> |
| #include <linux/blk-mq.h> |
| |
| #include "blk.h" |
| #include "blk-mq.h" |
| #include "blk-mq-tag.h" |
| |
| /* FLUSH/FUA sequences */ |
| enum { |
| REQ_FSEQ_PREFLUSH = (1 << 0), /* pre-flushing in progress */ |
| REQ_FSEQ_DATA = (1 << 1), /* data write in progress */ |
| REQ_FSEQ_POSTFLUSH = (1 << 2), /* post-flushing in progress */ |
| REQ_FSEQ_DONE = (1 << 3), |
| |
| REQ_FSEQ_ACTIONS = REQ_FSEQ_PREFLUSH | REQ_FSEQ_DATA | |
| REQ_FSEQ_POSTFLUSH, |
| |
| /* |
| * If flush has been pending longer than the following timeout, |
| * it's issued even if flush_data requests are still in flight. |
| */ |
| FLUSH_PENDING_TIMEOUT = 5 * HZ, |
| }; |
| |
| static bool blk_kick_flush(struct request_queue *q, |
| struct blk_flush_queue *fq); |
| |
| static unsigned int blk_flush_policy(unsigned long fflags, struct request *rq) |
| { |
| unsigned int policy = 0; |
| |
| if (blk_rq_sectors(rq)) |
| policy |= REQ_FSEQ_DATA; |
| |
| if (fflags & (1UL << QUEUE_FLAG_WC)) { |
| if (rq->cmd_flags & REQ_FLUSH) |
| policy |= REQ_FSEQ_PREFLUSH; |
| if (!(fflags & (1UL << QUEUE_FLAG_FUA)) && |
| (rq->cmd_flags & REQ_FUA)) |
| policy |= REQ_FSEQ_POSTFLUSH; |
| } |
| return policy; |
| } |
| |
| static unsigned int blk_flush_cur_seq(struct request *rq) |
| { |
| return 1 << ffz(rq->flush.seq); |
| } |
| |
| static void blk_flush_restore_request(struct request *rq) |
| { |
| /* |
| * After flush data completion, @rq->bio is %NULL but we need to |
| * complete the bio again. @rq->biotail is guaranteed to equal the |
| * original @rq->bio. Restore it. |
| */ |
| rq->bio = rq->biotail; |
| |
| /* make @rq a normal request */ |
| rq->cmd_flags &= ~REQ_FLUSH_SEQ; |
| rq->end_io = rq->flush.saved_end_io; |
| } |
| |
| static bool blk_flush_queue_rq(struct request *rq, bool add_front) |
| { |
| if (rq->q->mq_ops) { |
| struct request_queue *q = rq->q; |
| |
| blk_mq_add_to_requeue_list(rq, add_front); |
| blk_mq_kick_requeue_list(q); |
| return false; |
| } else { |
| if (add_front) |
| list_add(&rq->queuelist, &rq->q->queue_head); |
| else |
| list_add_tail(&rq->queuelist, &rq->q->queue_head); |
| return true; |
| } |
| } |
| |
| /** |
| * blk_flush_complete_seq - complete flush sequence |
| * @rq: FLUSH/FUA request being sequenced |
| * @fq: flush queue |
| * @seq: sequences to complete (mask of %REQ_FSEQ_*, can be zero) |
| * @error: whether an error occurred |
| * |
| * @rq just completed @seq part of its flush sequence, record the |
| * completion and trigger the next step. |
| * |
| * CONTEXT: |
| * spin_lock_irq(q->queue_lock or fq->mq_flush_lock) |
| * |
| * RETURNS: |
| * %true if requests were added to the dispatch queue, %false otherwise. |
| */ |
| static bool blk_flush_complete_seq(struct request *rq, |
| struct blk_flush_queue *fq, |
| unsigned int seq, int error) |
| { |
| struct request_queue *q = rq->q; |
| struct list_head *pending = &fq->flush_queue[fq->flush_pending_idx]; |
| bool queued = false, kicked; |
| |
| BUG_ON(rq->flush.seq & seq); |
| rq->flush.seq |= seq; |
| |
| if (likely(!error)) |
| seq = blk_flush_cur_seq(rq); |
| else |
| seq = REQ_FSEQ_DONE; |
| |
| switch (seq) { |
| case REQ_FSEQ_PREFLUSH: |
| case REQ_FSEQ_POSTFLUSH: |
| /* queue for flush */ |
| if (list_empty(pending)) |
| fq->flush_pending_since = jiffies; |
| list_move_tail(&rq->flush.list, pending); |
| break; |
| |
| case REQ_FSEQ_DATA: |
| list_move_tail(&rq->flush.list, &fq->flush_data_in_flight); |
| queued = blk_flush_queue_rq(rq, true); |
| break; |
| |
| case REQ_FSEQ_DONE: |
| /* |
| * @rq was previously adjusted by blk_flush_issue() for |
| * flush sequencing and may already have gone through the |
| * flush data request completion path. Restore @rq for |
| * normal completion and end it. |
| */ |
| BUG_ON(!list_empty(&rq->queuelist)); |
| list_del_init(&rq->flush.list); |
| blk_flush_restore_request(rq); |
| if (q->mq_ops) |
| blk_mq_end_request(rq, error); |
| else |
| __blk_end_request_all(rq, error); |
| break; |
| |
| default: |
| BUG(); |
| } |
| |
| kicked = blk_kick_flush(q, fq); |
| return kicked | queued; |
| } |
| |
| static void flush_end_io(struct request *flush_rq, int error) |
| { |
| struct request_queue *q = flush_rq->q; |
| struct list_head *running; |
| bool queued = false; |
| struct request *rq, *n; |
| unsigned long flags = 0; |
| struct blk_flush_queue *fq = blk_get_flush_queue(q, flush_rq->mq_ctx); |
| |
| if (q->mq_ops) { |
| struct blk_mq_hw_ctx *hctx; |
| |
| /* release the tag's ownership to the req cloned from */ |
| spin_lock_irqsave(&fq->mq_flush_lock, flags); |
| hctx = q->mq_ops->map_queue(q, flush_rq->mq_ctx->cpu); |
| blk_mq_tag_set_rq(hctx, flush_rq->tag, fq->orig_rq); |
| flush_rq->tag = -1; |
| } |
| |
| running = &fq->flush_queue[fq->flush_running_idx]; |
| BUG_ON(fq->flush_pending_idx == fq->flush_running_idx); |
| |
| /* account completion of the flush request */ |
| fq->flush_running_idx ^= 1; |
| |
| if (!q->mq_ops) |
| elv_completed_request(q, flush_rq); |
| |
| /* and push the waiting requests to the next stage */ |
| list_for_each_entry_safe(rq, n, running, flush.list) { |
| unsigned int seq = blk_flush_cur_seq(rq); |
| |
| BUG_ON(seq != REQ_FSEQ_PREFLUSH && seq != REQ_FSEQ_POSTFLUSH); |
| queued |= blk_flush_complete_seq(rq, fq, seq, error); |
| } |
| |
| /* |
| * Kick the queue to avoid stall for two cases: |
| * 1. Moving a request silently to empty queue_head may stall the |
| * queue. |
| * 2. When flush request is running in non-queueable queue, the |
| * queue is hold. Restart the queue after flush request is finished |
| * to avoid stall. |
| * This function is called from request completion path and calling |
| * directly into request_fn may confuse the driver. Always use |
| * kblockd. |
| */ |
| if (queued || fq->flush_queue_delayed) { |
| WARN_ON(q->mq_ops); |
| blk_run_queue_async(q); |
| } |
| fq->flush_queue_delayed = 0; |
| if (q->mq_ops) |
| spin_unlock_irqrestore(&fq->mq_flush_lock, flags); |
| } |
| |
| /** |
| * blk_kick_flush - consider issuing flush request |
| * @q: request_queue being kicked |
| * @fq: flush queue |
| * |
| * Flush related states of @q have changed, consider issuing flush request. |
| * Please read the comment at the top of this file for more info. |
| * |
| * CONTEXT: |
| * spin_lock_irq(q->queue_lock or fq->mq_flush_lock) |
| * |
| * RETURNS: |
| * %true if flush was issued, %false otherwise. |
| */ |
| static bool blk_kick_flush(struct request_queue *q, struct blk_flush_queue *fq) |
| { |
| struct list_head *pending = &fq->flush_queue[fq->flush_pending_idx]; |
| struct request *first_rq = |
| list_first_entry(pending, struct request, flush.list); |
| struct request *flush_rq = fq->flush_rq; |
| |
| /* C1 described at the top of this file */ |
| if (fq->flush_pending_idx != fq->flush_running_idx || list_empty(pending)) |
| return false; |
| |
| /* C2 and C3 */ |
| if (!list_empty(&fq->flush_data_in_flight) && |
| time_before(jiffies, |
| fq->flush_pending_since + FLUSH_PENDING_TIMEOUT)) |
| return false; |
| |
| /* |
| * Issue flush and toggle pending_idx. This makes pending_idx |
| * different from running_idx, which means flush is in flight. |
| */ |
| fq->flush_pending_idx ^= 1; |
| |
| blk_rq_init(q, flush_rq); |
| |
| /* |
| * Borrow tag from the first request since they can't |
| * be in flight at the same time. And acquire the tag's |
| * ownership for flush req. |
| */ |
| if (q->mq_ops) { |
| struct blk_mq_hw_ctx *hctx; |
| |
| flush_rq->mq_ctx = first_rq->mq_ctx; |
| flush_rq->tag = first_rq->tag; |
| fq->orig_rq = first_rq; |
| |
| hctx = q->mq_ops->map_queue(q, first_rq->mq_ctx->cpu); |
| blk_mq_tag_set_rq(hctx, first_rq->tag, flush_rq); |
| } |
| |
| flush_rq->cmd_type = REQ_TYPE_FS; |
| req_set_op_attrs(flush_rq, REQ_OP_FLUSH, WRITE_FLUSH | REQ_FLUSH_SEQ); |
| flush_rq->rq_disk = first_rq->rq_disk; |
| flush_rq->end_io = flush_end_io; |
| |
| return blk_flush_queue_rq(flush_rq, false); |
| } |
| |
| static void flush_data_end_io(struct request *rq, int error) |
| { |
| struct request_queue *q = rq->q; |
| struct blk_flush_queue *fq = blk_get_flush_queue(q, NULL); |
| |
| /* |
| * After populating an empty queue, kick it to avoid stall. Read |
| * the comment in flush_end_io(). |
| */ |
| if (blk_flush_complete_seq(rq, fq, REQ_FSEQ_DATA, error)) |
| blk_run_queue_async(q); |
| } |
| |
| static void mq_flush_data_end_io(struct request *rq, int error) |
| { |
| struct request_queue *q = rq->q; |
| struct blk_mq_hw_ctx *hctx; |
| struct blk_mq_ctx *ctx = rq->mq_ctx; |
| unsigned long flags; |
| struct blk_flush_queue *fq = blk_get_flush_queue(q, ctx); |
| |
| hctx = q->mq_ops->map_queue(q, ctx->cpu); |
| |
| /* |
| * After populating an empty queue, kick it to avoid stall. Read |
| * the comment in flush_end_io(). |
| */ |
| spin_lock_irqsave(&fq->mq_flush_lock, flags); |
| if (blk_flush_complete_seq(rq, fq, REQ_FSEQ_DATA, error)) |
| blk_mq_run_hw_queue(hctx, true); |
| spin_unlock_irqrestore(&fq->mq_flush_lock, flags); |
| } |
| |
| /** |
| * blk_insert_flush - insert a new FLUSH/FUA request |
| * @rq: request to insert |
| * |
| * To be called from __elv_add_request() for %ELEVATOR_INSERT_FLUSH insertions. |
| * or __blk_mq_run_hw_queue() to dispatch request. |
| * @rq is being submitted. Analyze what needs to be done and put it on the |
| * right queue. |
| * |
| * CONTEXT: |
| * spin_lock_irq(q->queue_lock) in !mq case |
| */ |
| void blk_insert_flush(struct request *rq) |
| { |
| struct request_queue *q = rq->q; |
| unsigned long fflags = q->queue_flags; /* may change, cache */ |
| unsigned int policy = blk_flush_policy(fflags, rq); |
| struct blk_flush_queue *fq = blk_get_flush_queue(q, rq->mq_ctx); |
| |
| /* |
| * @policy now records what operations need to be done. Adjust |
| * REQ_FLUSH and FUA for the driver. |
| */ |
| rq->cmd_flags &= ~REQ_FLUSH; |
| if (!(fflags & (1UL << QUEUE_FLAG_FUA))) |
| rq->cmd_flags &= ~REQ_FUA; |
| |
| /* |
| * An empty flush handed down from a stacking driver may |
| * translate into nothing if the underlying device does not |
| * advertise a write-back cache. In this case, simply |
| * complete the request. |
| */ |
| if (!policy) { |
| if (q->mq_ops) |
| blk_mq_end_request(rq, 0); |
| else |
| __blk_end_bidi_request(rq, 0, 0, 0); |
| return; |
| } |
| |
| BUG_ON(rq->bio != rq->biotail); /*assumes zero or single bio rq */ |
| |
| /* |
| * If there's data but flush is not necessary, the request can be |
| * processed directly without going through flush machinery. Queue |
| * for normal execution. |
| */ |
| if ((policy & REQ_FSEQ_DATA) && |
| !(policy & (REQ_FSEQ_PREFLUSH | REQ_FSEQ_POSTFLUSH))) { |
| if (q->mq_ops) { |
| blk_mq_insert_request(rq, false, false, true); |
| } else |
| list_add_tail(&rq->queuelist, &q->queue_head); |
| return; |
| } |
| |
| /* |
| * @rq should go through flush machinery. Mark it part of flush |
| * sequence and submit for further processing. |
| */ |
| memset(&rq->flush, 0, sizeof(rq->flush)); |
| INIT_LIST_HEAD(&rq->flush.list); |
| rq->cmd_flags |= REQ_FLUSH_SEQ; |
| rq->flush.saved_end_io = rq->end_io; /* Usually NULL */ |
| if (q->mq_ops) { |
| rq->end_io = mq_flush_data_end_io; |
| |
| spin_lock_irq(&fq->mq_flush_lock); |
| blk_flush_complete_seq(rq, fq, REQ_FSEQ_ACTIONS & ~policy, 0); |
| spin_unlock_irq(&fq->mq_flush_lock); |
| return; |
| } |
| rq->end_io = flush_data_end_io; |
| |
| blk_flush_complete_seq(rq, fq, REQ_FSEQ_ACTIONS & ~policy, 0); |
| } |
| |
| /** |
| * blkdev_issue_flush - queue a flush |
| * @bdev: blockdev to issue flush for |
| * @gfp_mask: memory allocation flags (for bio_alloc) |
| * @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. 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) |
| { |
| 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; |
| |
| /* |
| * some block devices may not have their queue correctly set up here |
| * (e.g. loop device without a backing file) and so issuing a flush |
| * here will panic. Ensure there is a request function before issuing |
| * the flush. |
| */ |
| if (!q->make_request_fn) |
| return -ENXIO; |
| |
| bio = bio_alloc(gfp_mask, 0); |
| bio->bi_bdev = bdev; |
| bio_set_op_attrs(bio, REQ_OP_WRITE, WRITE_FLUSH); |
| |
| ret = submit_bio_wait(bio); |
| |
| /* |
| * 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_iter.bi_sector; |
| |
| bio_put(bio); |
| return ret; |
| } |
| EXPORT_SYMBOL(blkdev_issue_flush); |
| |
| struct blk_flush_queue *blk_alloc_flush_queue(struct request_queue *q, |
| int node, int cmd_size) |
| { |
| struct blk_flush_queue *fq; |
| int rq_sz = sizeof(struct request); |
| |
| fq = kzalloc_node(sizeof(*fq), GFP_KERNEL, node); |
| if (!fq) |
| goto fail; |
| |
| if (q->mq_ops) { |
| spin_lock_init(&fq->mq_flush_lock); |
| rq_sz = round_up(rq_sz + cmd_size, cache_line_size()); |
| } |
| |
| fq->flush_rq = kzalloc_node(rq_sz, GFP_KERNEL, node); |
| if (!fq->flush_rq) |
| goto fail_rq; |
| |
| INIT_LIST_HEAD(&fq->flush_queue[0]); |
| INIT_LIST_HEAD(&fq->flush_queue[1]); |
| INIT_LIST_HEAD(&fq->flush_data_in_flight); |
| |
| return fq; |
| |
| fail_rq: |
| kfree(fq); |
| fail: |
| return NULL; |
| } |
| |
| void blk_free_flush_queue(struct blk_flush_queue *fq) |
| { |
| /* bio based request queue hasn't flush queue */ |
| if (!fq) |
| return; |
| |
| kfree(fq->flush_rq); |
| kfree(fq); |
| } |