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@ -1,6 +1,69 @@
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/*
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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_FLUSH makes sense, which
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* indicates a simple flush request. If there is data, REQ_FLUSH 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_FLUSH 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_FLUSH is
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* 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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* q->flush_queue[q->flush_pending_idx]. Once certain criteria are met, a
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* 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 REQ_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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@ -11,185 +74,290 @@
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/* FLUSH/FUA sequences */
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enum {
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QUEUE_FSEQ_STARTED = (1 << 0), /* flushing in progress */
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QUEUE_FSEQ_PREFLUSH = (1 << 1), /* pre-flushing in progress */
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QUEUE_FSEQ_DATA = (1 << 2), /* data write in progress */
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QUEUE_FSEQ_POSTFLUSH = (1 << 3), /* post-flushing in progress */
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QUEUE_FSEQ_DONE = (1 << 4),
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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 struct request *queue_next_fseq(struct request_queue *q);
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static bool blk_kick_flush(struct request_queue *q);
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unsigned blk_flush_cur_seq(struct request_queue *q)
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static unsigned int blk_flush_policy(unsigned int fflags, struct request *rq)
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{
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if (!q->flush_seq)
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return 0;
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return 1 << ffz(q->flush_seq);
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unsigned int policy = 0;
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if (fflags & REQ_FLUSH) {
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if (rq->cmd_flags & REQ_FLUSH)
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policy |= REQ_FSEQ_PREFLUSH;
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if (blk_rq_sectors(rq))
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policy |= REQ_FSEQ_DATA;
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if (!(fflags & REQ_FUA) && (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 struct request *blk_flush_complete_seq(struct request_queue *q,
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unsigned seq, int error)
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static unsigned int blk_flush_cur_seq(struct request *rq)
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{
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struct request *next_rq = NULL;
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if (error && !q->flush_err)
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q->flush_err = error;
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BUG_ON(q->flush_seq & seq);
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q->flush_seq |= seq;
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if (blk_flush_cur_seq(q) != QUEUE_FSEQ_DONE) {
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/* not complete yet, queue the next flush sequence */
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next_rq = queue_next_fseq(q);
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} else {
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/* complete this flush request */
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__blk_end_request_all(q->orig_flush_rq, q->flush_err);
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q->orig_flush_rq = NULL;
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q->flush_seq = 0;
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/* dispatch the next flush if there's one */
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if (!list_empty(&q->pending_flushes)) {
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next_rq = list_entry_rq(q->pending_flushes.next);
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list_move(&next_rq->queuelist, &q->queue_head);
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}
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}
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return next_rq;
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return 1 << ffz(rq->flush.seq);
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}
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static void blk_flush_complete_seq_end_io(struct request_queue *q,
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unsigned seq, int error)
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static void blk_flush_restore_request(struct request *rq)
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{
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bool was_empty = elv_queue_empty(q);
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struct request *next_rq;
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next_rq = blk_flush_complete_seq(q, seq, error);
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/*
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* Moving a request silently to empty queue_head may stall the
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* queue. Kick the queue in those cases.
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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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if (was_empty && next_rq)
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__blk_run_queue(q);
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rq->bio = rq->biotail;
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/* make @rq a normal request */
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rq->cmd_flags &= ~REQ_FLUSH_SEQ;
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rq->end_io = NULL;
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}
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static void pre_flush_end_io(struct request *rq, int error)
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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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* @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)
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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, unsigned int seq,
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int error)
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{
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elv_completed_request(rq->q, rq);
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blk_flush_complete_seq_end_io(rq->q, QUEUE_FSEQ_PREFLUSH, error);
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}
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struct request_queue *q = rq->q;
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struct list_head *pending = &q->flush_queue[q->flush_pending_idx];
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bool queued = false;
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static void flush_data_end_io(struct request *rq, int error)
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{
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elv_completed_request(rq->q, rq);
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blk_flush_complete_seq_end_io(rq->q, QUEUE_FSEQ_DATA, error);
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}
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BUG_ON(rq->flush.seq & seq);
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rq->flush.seq |= seq;
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static void post_flush_end_io(struct request *rq, int error)
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{
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elv_completed_request(rq->q, rq);
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blk_flush_complete_seq_end_io(rq->q, QUEUE_FSEQ_POSTFLUSH, error);
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}
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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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static void init_flush_request(struct request *rq, struct gendisk *disk)
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{
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rq->cmd_type = REQ_TYPE_FS;
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rq->cmd_flags = WRITE_FLUSH;
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rq->rq_disk = disk;
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}
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static struct request *queue_next_fseq(struct request_queue *q)
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{
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struct request *orig_rq = q->orig_flush_rq;
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struct request *rq = &q->flush_rq;
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blk_rq_init(q, rq);
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switch (blk_flush_cur_seq(q)) {
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case QUEUE_FSEQ_PREFLUSH:
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init_flush_request(rq, orig_rq->rq_disk);
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rq->end_io = pre_flush_end_io;
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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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q->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 QUEUE_FSEQ_DATA:
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init_request_from_bio(rq, orig_rq->bio);
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case REQ_FSEQ_DATA:
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list_move_tail(&rq->flush.list, &q->flush_data_in_flight);
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list_add(&rq->queuelist, &q->queue_head);
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queued = true;
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break;
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case REQ_FSEQ_DONE:
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/*
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* orig_rq->rq_disk may be different from
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* bio->bi_bdev->bd_disk if orig_rq got here through
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* remapping drivers. Make sure rq->rq_disk points
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* to the same one as orig_rq.
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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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rq->rq_disk = orig_rq->rq_disk;
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rq->cmd_flags &= ~(REQ_FLUSH | REQ_FUA);
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rq->cmd_flags |= orig_rq->cmd_flags & (REQ_FLUSH | REQ_FUA);
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rq->end_io = flush_data_end_io;
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break;
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case QUEUE_FSEQ_POSTFLUSH:
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init_flush_request(rq, orig_rq->rq_disk);
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rq->end_io = post_flush_end_io;
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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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__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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rq->cmd_flags |= REQ_FLUSH_SEQ;
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elv_insert(q, rq, ELEVATOR_INSERT_FRONT);
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return rq;
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return blk_kick_flush(q) | queued;
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}
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struct request *blk_do_flush(struct request_queue *q, struct request *rq)
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static void flush_end_io(struct request *flush_rq, int error)
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{
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unsigned int fflags = q->flush_flags; /* may change, cache it */
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bool has_flush = fflags & REQ_FLUSH, has_fua = fflags & REQ_FUA;
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bool do_preflush = has_flush && (rq->cmd_flags & REQ_FLUSH);
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bool do_postflush = has_flush && !has_fua && (rq->cmd_flags & REQ_FUA);
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unsigned skip = 0;
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struct request_queue *q = flush_rq->q;
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struct list_head *running = &q->flush_queue[q->flush_running_idx];
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bool was_empty = elv_queue_empty(q);
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bool queued = false;
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struct request *rq, *n;
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/*
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* Special case. If there's data but flush is not necessary,
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* the request can be issued directly.
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BUG_ON(q->flush_pending_idx == q->flush_running_idx);
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/* account completion of the flush request */
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q->flush_running_idx ^= 1;
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|
|
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, seq, error);
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
/* after populating an empty queue, kick it to avoid stall */
|
|
|
|
|
if (queued && was_empty)
|
|
|
|
|
__blk_run_queue(q);
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
/**
|
|
|
|
|
* blk_kick_flush - consider issuing flush request
|
|
|
|
|
* @q: request_queue being kicked
|
|
|
|
|
*
|
|
|
|
|
* Flush w/o data should be able to be issued directly too but
|
|
|
|
|
* currently some drivers assume that rq->bio contains
|
|
|
|
|
* non-zero data if it isn't NULL and empty FLUSH requests
|
|
|
|
|
* getting here usually have bio's without data.
|
|
|
|
|
* 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)
|
|
|
|
|
*
|
|
|
|
|
* RETURNS:
|
|
|
|
|
* %true if flush was issued, %false otherwise.
|
|
|
|
|
*/
|
|
|
|
|
static bool blk_kick_flush(struct request_queue *q)
|
|
|
|
|
{
|
|
|
|
|
struct list_head *pending = &q->flush_queue[q->flush_pending_idx];
|
|
|
|
|
struct request *first_rq =
|
|
|
|
|
list_first_entry(pending, struct request, flush.list);
|
|
|
|
|
|
|
|
|
|
/* C1 described at the top of this file */
|
|
|
|
|
if (q->flush_pending_idx != q->flush_running_idx || list_empty(pending))
|
|
|
|
|
return false;
|
|
|
|
|
|
|
|
|
|
/* C2 and C3 */
|
|
|
|
|
if (!list_empty(&q->flush_data_in_flight) &&
|
|
|
|
|
time_before(jiffies,
|
|
|
|
|
q->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.
|
|
|
|
|
*/
|
|
|
|
|
blk_rq_init(q, &q->flush_rq);
|
|
|
|
|
q->flush_rq.cmd_type = REQ_TYPE_FS;
|
|
|
|
|
q->flush_rq.cmd_flags = WRITE_FLUSH | REQ_FLUSH_SEQ;
|
|
|
|
|
q->flush_rq.rq_disk = first_rq->rq_disk;
|
|
|
|
|
q->flush_rq.end_io = flush_end_io;
|
|
|
|
|
|
|
|
|
|
q->flush_pending_idx ^= 1;
|
|
|
|
|
elv_insert(q, &q->flush_rq, ELEVATOR_INSERT_FRONT);
|
|
|
|
|
return true;
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
static void flush_data_end_io(struct request *rq, int error)
|
|
|
|
|
{
|
|
|
|
|
struct request_queue *q = rq->q;
|
|
|
|
|
bool was_empty = elv_queue_empty(q);
|
|
|
|
|
|
|
|
|
|
/* after populating an empty queue, kick it to avoid stall */
|
|
|
|
|
if (blk_flush_complete_seq(rq, REQ_FSEQ_DATA, error) && was_empty)
|
|
|
|
|
__blk_run_queue(q);
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
/**
|
|
|
|
|
* blk_insert_flush - insert a new FLUSH/FUA request
|
|
|
|
|
* @rq: request to insert
|
|
|
|
|
*
|
|
|
|
|
* To be called from elv_insert() for %ELEVATOR_INSERT_FLUSH insertions.
|
|
|
|
|
* @rq is being submitted. Analyze what needs to be done and put it on the
|
|
|
|
|
* right queue.
|
|
|
|
|
*
|
|
|
|
|
* CONTEXT:
|
|
|
|
|
* spin_lock_irq(q->queue_lock)
|
|
|
|
|
*/
|
|
|
|
|
void blk_insert_flush(struct request *rq)
|
|
|
|
|
{
|
|
|
|
|
struct request_queue *q = rq->q;
|
|
|
|
|
unsigned int fflags = q->flush_flags; /* may change, cache */
|
|
|
|
|
unsigned int policy = blk_flush_policy(fflags, rq);
|
|
|
|
|
|
|
|
|
|
BUG_ON(rq->end_io);
|
|
|
|
|
BUG_ON(!rq->bio || rq->bio != rq->biotail);
|
|
|
|
|
|
|
|
|
|
/*
|
|
|
|
|
* @policy now records what operations need to be done. Adjust
|
|
|
|
|
* REQ_FLUSH and FUA for the driver.
|
|
|
|
|
*/
|
|
|
|
|
if (blk_rq_sectors(rq) && !do_preflush && !do_postflush) {
|
|
|
|
|
rq->cmd_flags &= ~REQ_FLUSH;
|
|
|
|
|
if (!has_fua)
|
|
|
|
|
if (!(fflags & REQ_FUA))
|
|
|
|
|
rq->cmd_flags &= ~REQ_FUA;
|
|
|
|
|
return 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))) {
|
|
|
|
|
list_add(&rq->queuelist, &q->queue_head);
|
|
|
|
|
return;
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
/*
|
|
|
|
|
* Sequenced flushes can't be processed in parallel. If
|
|
|
|
|
* another one is already in progress, queue for later
|
|
|
|
|
* processing.
|
|
|
|
|
* @rq should go through flush machinery. Mark it part of flush
|
|
|
|
|
* sequence and submit for further processing.
|
|
|
|
|
*/
|
|
|
|
|
if (q->flush_seq) {
|
|
|
|
|
list_move_tail(&rq->queuelist, &q->pending_flushes);
|
|
|
|
|
return NULL;
|
|
|
|
|
memset(&rq->flush, 0, sizeof(rq->flush));
|
|
|
|
|
INIT_LIST_HEAD(&rq->flush.list);
|
|
|
|
|
rq->cmd_flags |= REQ_FLUSH_SEQ;
|
|
|
|
|
rq->end_io = flush_data_end_io;
|
|
|
|
|
|
|
|
|
|
blk_flush_complete_seq(rq, REQ_FSEQ_ACTIONS & ~policy, 0);
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
/**
|
|
|
|
|
* blk_abort_flushes - @q is being aborted, abort flush requests
|
|
|
|
|
* @q: request_queue being aborted
|
|
|
|
|
*
|
|
|
|
|
* To be called from elv_abort_queue(). @q is being aborted. Prepare all
|
|
|
|
|
* FLUSH/FUA requests for abortion.
|
|
|
|
|
*
|
|
|
|
|
* CONTEXT:
|
|
|
|
|
* spin_lock_irq(q->queue_lock)
|
|
|
|
|
*/
|
|
|
|
|
void blk_abort_flushes(struct request_queue *q)
|
|
|
|
|
{
|
|
|
|
|
struct request *rq, *n;
|
|
|
|
|
int i;
|
|
|
|
|
|
|
|
|
|
/*
|
|
|
|
|
* Requests in flight for data are already owned by the dispatch
|
|
|
|
|
* queue or the device driver. Just restore for normal completion.
|
|
|
|
|
*/
|
|
|
|
|
list_for_each_entry_safe(rq, n, &q->flush_data_in_flight, flush.list) {
|
|
|
|
|
list_del_init(&rq->flush.list);
|
|
|
|
|
blk_flush_restore_request(rq);
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
/*
|
|
|
|
|
* Start a new flush sequence
|
|
|
|
|
* We need to give away requests on flush queues. Restore for
|
|
|
|
|
* normal completion and put them on the dispatch queue.
|
|
|
|
|
*/
|
|
|
|
|
q->flush_err = 0;
|
|
|
|
|
q->flush_seq |= QUEUE_FSEQ_STARTED;
|
|
|
|
|
|
|
|
|
|
/* adjust FLUSH/FUA of the original request and stash it away */
|
|
|
|
|
rq->cmd_flags &= ~REQ_FLUSH;
|
|
|
|
|
if (!has_fua)
|
|
|
|
|
rq->cmd_flags &= ~REQ_FUA;
|
|
|
|
|
blk_dequeue_request(rq);
|
|
|
|
|
q->orig_flush_rq = rq;
|
|
|
|
|
|
|
|
|
|
/* skip unneded sequences and return the first one */
|
|
|
|
|
if (!do_preflush)
|
|
|
|
|
skip |= QUEUE_FSEQ_PREFLUSH;
|
|
|
|
|
if (!blk_rq_sectors(rq))
|
|
|
|
|
skip |= QUEUE_FSEQ_DATA;
|
|
|
|
|
if (!do_postflush)
|
|
|
|
|
skip |= QUEUE_FSEQ_POSTFLUSH;
|
|
|
|
|
return blk_flush_complete_seq(q, skip, 0);
|
|
|
|
|
for (i = 0; i < ARRAY_SIZE(q->flush_queue); i++) {
|
|
|
|
|
list_for_each_entry_safe(rq, n, &q->flush_queue[i],
|
|
|
|
|
flush.list) {
|
|
|
|
|
list_del_init(&rq->flush.list);
|
|
|
|
|
blk_flush_restore_request(rq);
|
|
|
|
|
list_add_tail(&rq->queuelist, &q->queue_head);
|
|
|
|
|
}
|
|
|
|
|
}
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
static void bio_end_flush(struct bio *bio, int err)
|
|
|
|
|