Merge branch 'mpi-master' into wip-k-fmlpwip-k-fmlp

Conflicts:
	litmus/sched_cedf.c

1 files changed, 443 insertions, 0 deletions

diff --git a/block/blk-flush.c b/block/blk-flush.c
new file mode 100644
index 000000000000..bb21e4c36f70
--- /dev/null
+++ b/block/blk-flush.c
@@ -0,0 +1,443 @@
+/*
+ * 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
+ * q->flush_queue[q->flush_pending_idx].  Once certain criteria are met, a
+ * 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 "blk.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);
+
+static unsigned int blk_flush_policy(unsigned int fflags, struct request *rq)
+{
+        unsigned int policy = 0;
+
+        if (fflags & REQ_FLUSH) {
+                if (rq->cmd_flags & REQ_FLUSH)
+                        policy |= REQ_FSEQ_PREFLUSH;
+                if (blk_rq_sectors(rq))
+                        policy |= REQ_FSEQ_DATA;
+                if (!(fflags & REQ_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 = NULL;
+}
+
+/**
+ * blk_flush_complete_seq - complete flush sequence
+ * @rq: FLUSH/FUA request being sequenced
+ * @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)
+ *
+ * RETURNS:
+ * %true if requests were added to the dispatch queue, %false otherwise.
+ */
+static bool blk_flush_complete_seq(struct request *rq, unsigned int seq,
+                                   int error)
+{
+        struct request_queue *q = rq->q;
+        struct list_head *pending = &q->flush_queue[q->flush_pending_idx];
+        bool queued = false;
+
+        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))
+                        q->flush_pending_since = jiffies;
+                list_move_tail(&rq->flush.list, pending);
+                break;
+
+        case REQ_FSEQ_DATA:
+                list_move_tail(&rq->flush.list, &q->flush_data_in_flight);
+                list_add(&rq->queuelist, &q->queue_head);
+                queued = 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);
+                __blk_end_request_all(rq, error);
+                break;
+
+        default:
+                BUG();
+        }
+
+        return blk_kick_flush(q) | queued;
+}
+
+static void flush_end_io(struct request *flush_rq, int error)
+{
+        struct request_queue *q = flush_rq->q;
+        struct list_head *running = &q->flush_queue[q->flush_running_idx];
+        bool queued = false;
+        struct request *rq, *n;
+
+        BUG_ON(q->flush_pending_idx == q->flush_running_idx);
+
+        /* account completion of the flush request */
+        q->flush_running_idx ^= 1;
+        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);
+        }
+
+        /*
+         * 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 || q->flush_queue_delayed)
+                blk_run_queue_async(q);
+        q->flush_queue_delayed = 0;
+}
+
+/**
+ * blk_kick_flush - consider issuing flush request
+ * @q: request_queue being kicked
+ *
+ * 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;
+        list_add_tail(&q->flush_rq.queuelist, &q->queue_head);
+        return true;
+}
+
+static void flush_data_end_io(struct request *rq, int error)
+{
+        struct request_queue *q = rq->q;
+
+        /*
+         * After populating an empty queue, kick it to avoid stall.  Read
+         * the comment in flush_end_io().
+         */
+        if (blk_flush_complete_seq(rq, REQ_FSEQ_DATA, error))
+                blk_run_queue_async(q);
+}
+
+/**
+ * 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.
+ * @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.
+         */
+        rq->cmd_flags &= ~REQ_FLUSH;
+        if (!(fflags & REQ_FUA))
+                rq->cmd_flags &= ~REQ_FUA;
+
+        /*
+         * 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_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->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);
+        }
+
+        /*
+         * We need to give away requests on flush queues.  Restore for
+         * normal completion and put them on the dispatch queue.
+         */
+        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)
+{
+        if (err)
+                clear_bit(BIO_UPTODATE, &bio->bi_flags);
+        if (bio->bi_private)
+                complete(bio->bi_private);
+        bio_put(bio);
+}
+
+/**
+ * blkdev_issue_flush - queue a flush
+ * @bdev:       blockdev to issue flush for
+ * @gfp_mask:   memory allocation flags (for bio_alloc)
+ * @error_sector:       error sector
+ *
+ * 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)
+{
+        DECLARE_COMPLETION_ONSTACK(wait);
+        struct request_queue *q;
+        struct bio *bio;
+        int ret = 0;
+
+        if (bdev->bd_disk == NULL)
+                return -ENXIO;
+
+        q = bdev_get_queue(bdev);
+        if (!q)
+                return -ENXIO;
+
+        /*
+         * 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_end_io = bio_end_flush;
+        bio->bi_bdev = bdev;
+        bio->bi_private = &wait;
+
+        bio_get(bio);
+        submit_bio(WRITE_FLUSH, 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 blk_rq_pos(rq).
+         */
+        if (error_sector)
+               *error_sector = bio->bi_sector;
+
+        if (!bio_flagged(bio, BIO_UPTODATE))
+                ret = -EIO;
+
+        bio_put(bio);
+        return ret;
+}
+EXPORT_SYMBOL(blkdev_issue_flush);