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36869cb93d
Pull block layer updates from Jens Axboe: "This is the main block pull request this series. Contrary to previous release, I've kept the core and driver changes in the same branch. We always ended up having dependencies between the two for obvious reasons, so makes more sense to keep them together. That said, I'll probably try and keep more topical branches going forward, especially for cycles that end up being as busy as this one. The major parts of this pull request is: - Improved support for O_DIRECT on block devices, with a small private implementation instead of using the pig that is fs/direct-io.c. From Christoph. - Request completion tracking in a scalable fashion. This is utilized by two components in this pull, the new hybrid polling and the writeback queue throttling code. - Improved support for polling with O_DIRECT, adding a hybrid mode that combines pure polling with an initial sleep. From me. - Support for automatic throttling of writeback queues on the block side. This uses feedback from the device completion latencies to scale the queue on the block side up or down. From me. - Support from SMR drives in the block layer and for SD. From Hannes and Shaun. - Multi-connection support for nbd. From Josef. - Cleanup of request and bio flags, so we have a clear split between which are bio (or rq) private, and which ones are shared. From Christoph. - A set of patches from Bart, that improve how we handle queue stopping and starting in blk-mq. - Support for WRITE_ZEROES from Chaitanya. - Lightnvm updates from Javier/Matias. - Supoort for FC for the nvme-over-fabrics code. From James Smart. - A bunch of fixes from a whole slew of people, too many to name here" * 'for-4.10/block' of git://git.kernel.dk/linux-block: (182 commits) blk-stat: fix a few cases of missing batch flushing blk-flush: run the queue when inserting blk-mq flush elevator: make the rqhash helpers exported blk-mq: abstract out blk_mq_dispatch_rq_list() helper blk-mq: add blk_mq_start_stopped_hw_queue() block: improve handling of the magic discard payload blk-wbt: don't throttle discard or write zeroes nbd: use dev_err_ratelimited in io path nbd: reset the setup task for NBD_CLEAR_SOCK nvme-fabrics: Add FC LLDD loopback driver to test FC-NVME nvme-fabrics: Add target support for FC transport nvme-fabrics: Add host support for FC transport nvme-fabrics: Add FC transport LLDD api definitions nvme-fabrics: Add FC transport FC-NVME definitions nvme-fabrics: Add FC transport error codes to nvme.h Add type 0x28 NVME type code to scsi fc headers nvme-fabrics: patch target code in prep for FC transport support nvme-fabrics: set sqe.command_id in core not transports parser: add u64 number parser nvme-rdma: align to generic ib_event logging helper ...
578 lines
16 KiB
C
578 lines
16 KiB
C
/*
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* Functions to sequence FLUSH and FUA writes.
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*
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* Copyright (C) 2011 Max Planck Institute for Gravitational Physics
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* Copyright (C) 2011 Tejun Heo <tj@kernel.org>
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*
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* This file is released under the GPLv2.
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*
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* REQ_{FLUSH|FUA} requests are decomposed to sequences consisted of three
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* optional steps - PREFLUSH, DATA and POSTFLUSH - according to the request
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* properties and hardware capability.
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*
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* If a request doesn't have data, only REQ_PREFLUSH makes sense, which
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* indicates a simple flush request. If there is data, REQ_PREFLUSH indicates
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* that the device cache should be flushed before the data is executed, and
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* REQ_FUA means that the data must be on non-volatile media on request
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* completion.
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*
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* If the device doesn't have writeback cache, FLUSH and FUA don't make any
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* difference. The requests are either completed immediately if there's no
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* data or executed as normal requests otherwise.
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*
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* If the device has writeback cache and supports FUA, REQ_PREFLUSH is
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* translated to PREFLUSH but REQ_FUA is passed down directly with DATA.
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*
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* If the device has writeback cache and doesn't support FUA, REQ_PREFLUSH
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* is translated to PREFLUSH and REQ_FUA to POSTFLUSH.
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*
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* The actual execution of flush is double buffered. Whenever a request
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* needs to execute PRE or POSTFLUSH, it queues at
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* fq->flush_queue[fq->flush_pending_idx]. Once certain criteria are met, a
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* REQ_OP_FLUSH is issued and the pending_idx is toggled. When the flush
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* completes, all the requests which were pending are proceeded to the next
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* step. This allows arbitrary merging of different types of FLUSH/FUA
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* requests.
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*
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* Currently, the following conditions are used to determine when to issue
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* flush.
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*
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* C1. At any given time, only one flush shall be in progress. This makes
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* double buffering sufficient.
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*
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* C2. Flush is deferred if any request is executing DATA of its sequence.
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* This avoids issuing separate POSTFLUSHes for requests which shared
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* PREFLUSH.
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*
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* C3. The second condition is ignored if there is a request which has
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* waited longer than FLUSH_PENDING_TIMEOUT. This is to avoid
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* starvation in the unlikely case where there are continuous stream of
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* FUA (without FLUSH) requests.
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*
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* For devices which support FUA, it isn't clear whether C2 (and thus C3)
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* is beneficial.
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*
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* Note that a sequenced FLUSH/FUA request with DATA is completed twice.
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* Once while executing DATA and again after the whole sequence is
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* complete. The first completion updates the contained bio but doesn't
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* finish it so that the bio submitter is notified only after the whole
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* sequence is complete. This is implemented by testing RQF_FLUSH_SEQ in
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* req_bio_endio().
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*
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* The above peculiarity requires that each FLUSH/FUA request has only one
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* bio attached to it, which is guaranteed as they aren't allowed to be
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* merged in the usual way.
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*/
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#include <linux/kernel.h>
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#include <linux/module.h>
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#include <linux/bio.h>
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#include <linux/blkdev.h>
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#include <linux/gfp.h>
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#include <linux/blk-mq.h>
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#include "blk.h"
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#include "blk-mq.h"
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#include "blk-mq-tag.h"
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/* FLUSH/FUA sequences */
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enum {
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REQ_FSEQ_PREFLUSH = (1 << 0), /* pre-flushing in progress */
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REQ_FSEQ_DATA = (1 << 1), /* data write in progress */
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REQ_FSEQ_POSTFLUSH = (1 << 2), /* post-flushing in progress */
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REQ_FSEQ_DONE = (1 << 3),
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REQ_FSEQ_ACTIONS = REQ_FSEQ_PREFLUSH | REQ_FSEQ_DATA |
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REQ_FSEQ_POSTFLUSH,
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/*
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* If flush has been pending longer than the following timeout,
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* it's issued even if flush_data requests are still in flight.
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*/
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FLUSH_PENDING_TIMEOUT = 5 * HZ,
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};
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static bool blk_kick_flush(struct request_queue *q,
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struct blk_flush_queue *fq);
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static unsigned int blk_flush_policy(unsigned long fflags, struct request *rq)
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{
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unsigned int policy = 0;
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if (blk_rq_sectors(rq))
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policy |= REQ_FSEQ_DATA;
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if (fflags & (1UL << QUEUE_FLAG_WC)) {
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if (rq->cmd_flags & REQ_PREFLUSH)
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policy |= REQ_FSEQ_PREFLUSH;
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if (!(fflags & (1UL << QUEUE_FLAG_FUA)) &&
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(rq->cmd_flags & REQ_FUA))
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policy |= REQ_FSEQ_POSTFLUSH;
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}
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return policy;
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}
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static unsigned int blk_flush_cur_seq(struct request *rq)
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{
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return 1 << ffz(rq->flush.seq);
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}
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static void blk_flush_restore_request(struct request *rq)
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{
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/*
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* After flush data completion, @rq->bio is %NULL but we need to
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* complete the bio again. @rq->biotail is guaranteed to equal the
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* original @rq->bio. Restore it.
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*/
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rq->bio = rq->biotail;
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/* make @rq a normal request */
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rq->rq_flags &= ~RQF_FLUSH_SEQ;
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rq->end_io = rq->flush.saved_end_io;
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}
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static bool blk_flush_queue_rq(struct request *rq, bool add_front)
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{
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if (rq->q->mq_ops) {
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blk_mq_add_to_requeue_list(rq, add_front, true);
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return false;
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} else {
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if (add_front)
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list_add(&rq->queuelist, &rq->q->queue_head);
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else
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list_add_tail(&rq->queuelist, &rq->q->queue_head);
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return true;
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}
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}
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/**
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* blk_flush_complete_seq - complete flush sequence
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* @rq: FLUSH/FUA request being sequenced
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* @fq: flush queue
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* @seq: sequences to complete (mask of %REQ_FSEQ_*, can be zero)
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* @error: whether an error occurred
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*
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* @rq just completed @seq part of its flush sequence, record the
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* completion and trigger the next step.
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*
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* CONTEXT:
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* spin_lock_irq(q->queue_lock or fq->mq_flush_lock)
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*
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* RETURNS:
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* %true if requests were added to the dispatch queue, %false otherwise.
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*/
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static bool blk_flush_complete_seq(struct request *rq,
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struct blk_flush_queue *fq,
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unsigned int seq, int error)
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{
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struct request_queue *q = rq->q;
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struct list_head *pending = &fq->flush_queue[fq->flush_pending_idx];
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bool queued = false, kicked;
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BUG_ON(rq->flush.seq & seq);
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rq->flush.seq |= seq;
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if (likely(!error))
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seq = blk_flush_cur_seq(rq);
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else
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seq = REQ_FSEQ_DONE;
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switch (seq) {
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case REQ_FSEQ_PREFLUSH:
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case REQ_FSEQ_POSTFLUSH:
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/* queue for flush */
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if (list_empty(pending))
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fq->flush_pending_since = jiffies;
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list_move_tail(&rq->flush.list, pending);
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break;
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case REQ_FSEQ_DATA:
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list_move_tail(&rq->flush.list, &fq->flush_data_in_flight);
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queued = blk_flush_queue_rq(rq, true);
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break;
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case REQ_FSEQ_DONE:
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/*
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* @rq was previously adjusted by blk_flush_issue() for
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* flush sequencing and may already have gone through the
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* flush data request completion path. Restore @rq for
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* normal completion and end it.
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*/
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BUG_ON(!list_empty(&rq->queuelist));
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list_del_init(&rq->flush.list);
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blk_flush_restore_request(rq);
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if (q->mq_ops)
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blk_mq_end_request(rq, error);
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else
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__blk_end_request_all(rq, error);
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break;
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default:
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BUG();
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}
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kicked = blk_kick_flush(q, fq);
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return kicked | queued;
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}
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static void flush_end_io(struct request *flush_rq, int error)
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{
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struct request_queue *q = flush_rq->q;
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struct list_head *running;
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bool queued = false;
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struct request *rq, *n;
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unsigned long flags = 0;
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struct blk_flush_queue *fq = blk_get_flush_queue(q, flush_rq->mq_ctx);
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if (q->mq_ops) {
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struct blk_mq_hw_ctx *hctx;
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/* release the tag's ownership to the req cloned from */
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spin_lock_irqsave(&fq->mq_flush_lock, flags);
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hctx = blk_mq_map_queue(q, flush_rq->mq_ctx->cpu);
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blk_mq_tag_set_rq(hctx, flush_rq->tag, fq->orig_rq);
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flush_rq->tag = -1;
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}
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running = &fq->flush_queue[fq->flush_running_idx];
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BUG_ON(fq->flush_pending_idx == fq->flush_running_idx);
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/* account completion of the flush request */
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fq->flush_running_idx ^= 1;
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if (!q->mq_ops)
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elv_completed_request(q, flush_rq);
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/* and push the waiting requests to the next stage */
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list_for_each_entry_safe(rq, n, running, flush.list) {
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unsigned int seq = blk_flush_cur_seq(rq);
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BUG_ON(seq != REQ_FSEQ_PREFLUSH && seq != REQ_FSEQ_POSTFLUSH);
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queued |= blk_flush_complete_seq(rq, fq, seq, error);
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}
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/*
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* Kick the queue to avoid stall for two cases:
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* 1. Moving a request silently to empty queue_head may stall the
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* queue.
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* 2. When flush request is running in non-queueable queue, the
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* queue is hold. Restart the queue after flush request is finished
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* to avoid stall.
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* This function is called from request completion path and calling
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* directly into request_fn may confuse the driver. Always use
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* kblockd.
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*/
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if (queued || fq->flush_queue_delayed) {
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WARN_ON(q->mq_ops);
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blk_run_queue_async(q);
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}
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fq->flush_queue_delayed = 0;
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if (q->mq_ops)
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spin_unlock_irqrestore(&fq->mq_flush_lock, flags);
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}
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/**
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* blk_kick_flush - consider issuing flush request
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* @q: request_queue being kicked
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* @fq: flush queue
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*
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* Flush related states of @q have changed, consider issuing flush request.
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* Please read the comment at the top of this file for more info.
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*
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* CONTEXT:
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* spin_lock_irq(q->queue_lock or fq->mq_flush_lock)
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*
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* RETURNS:
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* %true if flush was issued, %false otherwise.
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*/
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static bool blk_kick_flush(struct request_queue *q, struct blk_flush_queue *fq)
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{
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struct list_head *pending = &fq->flush_queue[fq->flush_pending_idx];
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struct request *first_rq =
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list_first_entry(pending, struct request, flush.list);
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struct request *flush_rq = fq->flush_rq;
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/* C1 described at the top of this file */
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if (fq->flush_pending_idx != fq->flush_running_idx || list_empty(pending))
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return false;
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/* C2 and C3 */
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if (!list_empty(&fq->flush_data_in_flight) &&
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time_before(jiffies,
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fq->flush_pending_since + FLUSH_PENDING_TIMEOUT))
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return false;
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/*
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* Issue flush and toggle pending_idx. This makes pending_idx
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* different from running_idx, which means flush is in flight.
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*/
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fq->flush_pending_idx ^= 1;
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blk_rq_init(q, flush_rq);
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/*
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* Borrow tag from the first request since they can't
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* be in flight at the same time. And acquire the tag's
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* ownership for flush req.
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*/
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if (q->mq_ops) {
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struct blk_mq_hw_ctx *hctx;
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flush_rq->mq_ctx = first_rq->mq_ctx;
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flush_rq->tag = first_rq->tag;
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fq->orig_rq = first_rq;
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hctx = blk_mq_map_queue(q, first_rq->mq_ctx->cpu);
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blk_mq_tag_set_rq(hctx, first_rq->tag, flush_rq);
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}
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flush_rq->cmd_type = REQ_TYPE_FS;
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flush_rq->cmd_flags = REQ_OP_FLUSH | REQ_PREFLUSH;
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flush_rq->rq_flags |= RQF_FLUSH_SEQ;
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flush_rq->rq_disk = first_rq->rq_disk;
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flush_rq->end_io = flush_end_io;
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return blk_flush_queue_rq(flush_rq, false);
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}
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static void flush_data_end_io(struct request *rq, int error)
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{
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struct request_queue *q = rq->q;
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struct blk_flush_queue *fq = blk_get_flush_queue(q, NULL);
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/*
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* Updating q->in_flight[] here for making this tag usable
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* early. Because in blk_queue_start_tag(),
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* q->in_flight[BLK_RW_ASYNC] is used to limit async I/O and
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* reserve tags for sync I/O.
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*
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* More importantly this way can avoid the following I/O
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* deadlock:
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*
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* - suppose there are 40 fua requests comming to flush queue
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* and queue depth is 31
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* - 30 rqs are scheduled then blk_queue_start_tag() can't alloc
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* tag for async I/O any more
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* - all the 30 rqs are completed before FLUSH_PENDING_TIMEOUT
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* and flush_data_end_io() is called
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* - the other rqs still can't go ahead if not updating
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* q->in_flight[BLK_RW_ASYNC] here, meantime these rqs
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* are held in flush data queue and make no progress of
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* handling post flush rq
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* - only after the post flush rq is handled, all these rqs
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* can be completed
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*/
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elv_completed_request(q, rq);
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/* for avoiding double accounting */
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rq->rq_flags &= ~RQF_STARTED;
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/*
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* After populating an empty queue, kick it to avoid stall. Read
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* the comment in flush_end_io().
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*/
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if (blk_flush_complete_seq(rq, fq, REQ_FSEQ_DATA, error))
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blk_run_queue_async(q);
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}
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static void mq_flush_data_end_io(struct request *rq, int error)
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{
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struct request_queue *q = rq->q;
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struct blk_mq_hw_ctx *hctx;
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struct blk_mq_ctx *ctx = rq->mq_ctx;
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unsigned long flags;
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struct blk_flush_queue *fq = blk_get_flush_queue(q, ctx);
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hctx = blk_mq_map_queue(q, ctx->cpu);
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/*
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* After populating an empty queue, kick it to avoid stall. Read
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* the comment in flush_end_io().
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*/
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spin_lock_irqsave(&fq->mq_flush_lock, flags);
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if (blk_flush_complete_seq(rq, fq, REQ_FSEQ_DATA, error))
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blk_mq_run_hw_queue(hctx, true);
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spin_unlock_irqrestore(&fq->mq_flush_lock, flags);
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}
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/**
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* blk_insert_flush - insert a new FLUSH/FUA request
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* @rq: request to insert
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*
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* To be called from __elv_add_request() for %ELEVATOR_INSERT_FLUSH insertions.
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* or __blk_mq_run_hw_queue() to dispatch request.
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* @rq is being submitted. Analyze what needs to be done and put it on the
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* right queue.
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*
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* CONTEXT:
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* spin_lock_irq(q->queue_lock) in !mq case
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*/
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void blk_insert_flush(struct request *rq)
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{
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struct request_queue *q = rq->q;
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unsigned long fflags = q->queue_flags; /* may change, cache */
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unsigned int policy = blk_flush_policy(fflags, rq);
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struct blk_flush_queue *fq = blk_get_flush_queue(q, rq->mq_ctx);
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/*
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* @policy now records what operations need to be done. Adjust
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* REQ_PREFLUSH and FUA for the driver.
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*/
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rq->cmd_flags &= ~REQ_PREFLUSH;
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if (!(fflags & (1UL << QUEUE_FLAG_FUA)))
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rq->cmd_flags &= ~REQ_FUA;
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/*
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* REQ_PREFLUSH|REQ_FUA implies REQ_SYNC, so if we clear any
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* of those flags, we have to set REQ_SYNC to avoid skewing
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* the request accounting.
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*/
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rq->cmd_flags |= REQ_SYNC;
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/*
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* An empty flush handed down from a stacking driver may
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* 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, true, false);
|
|
} 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->rq_flags |= RQF_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->bi_opf = REQ_OP_WRITE | REQ_PREFLUSH;
|
|
|
|
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);
|
|
}
|