1 files changed, 319 insertions, 0 deletions

diff --git a/block/blk-barrier.c b/block/blk-barrier.c
new file mode 100644
index 000000000000..5f74fec327d5
--- /dev/null
+++ b/block/blk-barrier.c
@@ -0,0 +1,319 @@
+/*
+ * Functions related to barrier IO handling
+ */
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/bio.h>
+#include <linux/blkdev.h>
+
+#include "blk.h"
+
+/**
+ * blk_queue_ordered - does this queue support ordered writes
+ * @q:        the request queue
+ * @ordered:  one of QUEUE_ORDERED_*
+ * @prepare_flush_fn: rq setup helper for cache flush ordered writes
+ *
+ * Description:
+ *   For journalled file systems, doing ordered writes on a commit
+ *   block instead of explicitly doing wait_on_buffer (which is bad
+ *   for performance) can be a big win. Block drivers supporting this
+ *   feature should call this function and indicate so.
+ *
+ **/
+int blk_queue_ordered(struct request_queue *q, unsigned ordered,
+                      prepare_flush_fn *prepare_flush_fn)
+{
+        if (ordered & (QUEUE_ORDERED_PREFLUSH | QUEUE_ORDERED_POSTFLUSH) &&
+            prepare_flush_fn == NULL) {
+                printk(KERN_ERR "blk_queue_ordered: prepare_flush_fn required\n");
+                return -EINVAL;
+        }
+
+        if (ordered != QUEUE_ORDERED_NONE &&
+            ordered != QUEUE_ORDERED_DRAIN &&
+            ordered != QUEUE_ORDERED_DRAIN_FLUSH &&
+            ordered != QUEUE_ORDERED_DRAIN_FUA &&
+            ordered != QUEUE_ORDERED_TAG &&
+            ordered != QUEUE_ORDERED_TAG_FLUSH &&
+            ordered != QUEUE_ORDERED_TAG_FUA) {
+                printk(KERN_ERR "blk_queue_ordered: bad value %d\n", ordered);
+                return -EINVAL;
+        }
+
+        q->ordered = ordered;
+        q->next_ordered = ordered;
+        q->prepare_flush_fn = prepare_flush_fn;
+
+        return 0;
+}
+
+EXPORT_SYMBOL(blk_queue_ordered);
+
+/*
+ * Cache flushing for ordered writes handling
+ */
+inline unsigned blk_ordered_cur_seq(struct request_queue *q)
+{
+        if (!q->ordseq)
+                return 0;
+        return 1 << ffz(q->ordseq);
+}
+
+unsigned blk_ordered_req_seq(struct request *rq)
+{
+        struct request_queue *q = rq->q;
+
+        BUG_ON(q->ordseq == 0);
+
+        if (rq == &q->pre_flush_rq)
+                return QUEUE_ORDSEQ_PREFLUSH;
+        if (rq == &q->bar_rq)
+                return QUEUE_ORDSEQ_BAR;
+        if (rq == &q->post_flush_rq)
+                return QUEUE_ORDSEQ_POSTFLUSH;
+
+        /*
+         * !fs requests don't need to follow barrier ordering.  Always
+         * put them at the front.  This fixes the following deadlock.
+         *
+         * http://thread.gmane.org/gmane.linux.kernel/537473
+         */
+        if (!blk_fs_request(rq))
+                return QUEUE_ORDSEQ_DRAIN;
+
+        if ((rq->cmd_flags & REQ_ORDERED_COLOR) ==
+            (q->orig_bar_rq->cmd_flags & REQ_ORDERED_COLOR))
+                return QUEUE_ORDSEQ_DRAIN;
+        else
+                return QUEUE_ORDSEQ_DONE;
+}
+
+void blk_ordered_complete_seq(struct request_queue *q, unsigned seq, int error)
+{
+        struct request *rq;
+
+        if (error && !q->orderr)
+                q->orderr = error;
+
+        BUG_ON(q->ordseq & seq);
+        q->ordseq |= seq;
+
+        if (blk_ordered_cur_seq(q) != QUEUE_ORDSEQ_DONE)
+                return;
+
+        /*
+         * Okay, sequence complete.
+         */
+        q->ordseq = 0;
+        rq = q->orig_bar_rq;
+
+        if (__blk_end_request(rq, q->orderr, blk_rq_bytes(rq)))
+                BUG();
+}
+
+static void pre_flush_end_io(struct request *rq, int error)
+{
+        elv_completed_request(rq->q, rq);
+        blk_ordered_complete_seq(rq->q, QUEUE_ORDSEQ_PREFLUSH, error);
+}
+
+static void bar_end_io(struct request *rq, int error)
+{
+        elv_completed_request(rq->q, rq);
+        blk_ordered_complete_seq(rq->q, QUEUE_ORDSEQ_BAR, error);
+}
+
+static void post_flush_end_io(struct request *rq, int error)
+{
+        elv_completed_request(rq->q, rq);
+        blk_ordered_complete_seq(rq->q, QUEUE_ORDSEQ_POSTFLUSH, error);
+}
+
+static void queue_flush(struct request_queue *q, unsigned which)
+{
+        struct request *rq;
+        rq_end_io_fn *end_io;
+
+        if (which == QUEUE_ORDERED_PREFLUSH) {
+                rq = &q->pre_flush_rq;
+                end_io = pre_flush_end_io;
+        } else {
+                rq = &q->post_flush_rq;
+                end_io = post_flush_end_io;
+        }
+
+        rq->cmd_flags = REQ_HARDBARRIER;
+        rq_init(q, rq);
+        rq->elevator_private = NULL;
+        rq->elevator_private2 = NULL;
+        rq->rq_disk = q->bar_rq.rq_disk;
+        rq->end_io = end_io;
+        q->prepare_flush_fn(q, rq);
+
+        elv_insert(q, rq, ELEVATOR_INSERT_FRONT);
+}
+
+static inline struct request *start_ordered(struct request_queue *q,
+                                            struct request *rq)
+{
+        q->orderr = 0;
+        q->ordered = q->next_ordered;
+        q->ordseq |= QUEUE_ORDSEQ_STARTED;
+
+        /*
+         * Prep proxy barrier request.
+         */
+        blkdev_dequeue_request(rq);
+        q->orig_bar_rq = rq;
+        rq = &q->bar_rq;
+        rq->cmd_flags = 0;
+        rq_init(q, rq);
+        if (bio_data_dir(q->orig_bar_rq->bio) == WRITE)
+                rq->cmd_flags |= REQ_RW;
+        if (q->ordered & QUEUE_ORDERED_FUA)
+                rq->cmd_flags |= REQ_FUA;
+        rq->elevator_private = NULL;
+        rq->elevator_private2 = NULL;
+        init_request_from_bio(rq, q->orig_bar_rq->bio);
+        rq->end_io = bar_end_io;
+
+        /*
+         * Queue ordered sequence.  As we stack them at the head, we
+         * need to queue in reverse order.  Note that we rely on that
+         * no fs request uses ELEVATOR_INSERT_FRONT and thus no fs
+         * request gets inbetween ordered sequence. If this request is
+         * an empty barrier, we don't need to do a postflush ever since
+         * there will be no data written between the pre and post flush.
+         * Hence a single flush will suffice.
+         */
+        if ((q->ordered & QUEUE_ORDERED_POSTFLUSH) && !blk_empty_barrier(rq))
+                queue_flush(q, QUEUE_ORDERED_POSTFLUSH);
+        else
+                q->ordseq |= QUEUE_ORDSEQ_POSTFLUSH;
+
+        elv_insert(q, rq, ELEVATOR_INSERT_FRONT);
+
+        if (q->ordered & QUEUE_ORDERED_PREFLUSH) {
+                queue_flush(q, QUEUE_ORDERED_PREFLUSH);
+                rq = &q->pre_flush_rq;
+        } else
+                q->ordseq |= QUEUE_ORDSEQ_PREFLUSH;
+
+        if ((q->ordered & QUEUE_ORDERED_TAG) || q->in_flight == 0)
+                q->ordseq |= QUEUE_ORDSEQ_DRAIN;
+        else
+                rq = NULL;
+
+        return rq;
+}
+
+int blk_do_ordered(struct request_queue *q, struct request **rqp)
+{
+        struct request *rq = *rqp;
+        const int is_barrier = blk_fs_request(rq) && blk_barrier_rq(rq);
+
+        if (!q->ordseq) {
+                if (!is_barrier)
+                        return 1;
+
+                if (q->next_ordered != QUEUE_ORDERED_NONE) {
+                        *rqp = start_ordered(q, rq);
+                        return 1;
+                } else {
+                        /*
+                         * This can happen when the queue switches to
+                         * ORDERED_NONE while this request is on it.
+                         */
+                        blkdev_dequeue_request(rq);
+                        if (__blk_end_request(rq, -EOPNOTSUPP,
+                                              blk_rq_bytes(rq)))
+                                BUG();
+                        *rqp = NULL;
+                        return 0;
+                }
+        }
+
+        /*
+         * Ordered sequence in progress
+         */
+
+        /* Special requests are not subject to ordering rules. */
+        if (!blk_fs_request(rq) &&
+            rq != &q->pre_flush_rq && rq != &q->post_flush_rq)
+                return 1;
+
+        if (q->ordered & QUEUE_ORDERED_TAG) {
+                /* Ordered by tag.  Blocking the next barrier is enough. */
+                if (is_barrier && rq != &q->bar_rq)
+                        *rqp = NULL;
+        } else {
+                /* Ordered by draining.  Wait for turn. */
+                WARN_ON(blk_ordered_req_seq(rq) < blk_ordered_cur_seq(q));
+                if (blk_ordered_req_seq(rq) > blk_ordered_cur_seq(q))
+                        *rqp = NULL;
+        }
+
+        return 1;
+}
+
+static void bio_end_empty_barrier(struct bio *bio, int err)
+{
+        if (err)
+                clear_bit(BIO_UPTODATE, &bio->bi_flags);
+
+        complete(bio->bi_private);
+}
+
+/**
+ * blkdev_issue_flush - queue a flush
+ * @bdev:       blockdev to issue flush for
+ * @error_sector:       error sector
+ *
+ * Description:
+ *    Issue a flush for the block device in question. Caller can supply
+ *    room for storing the error offset in case of a flush error, if they
+ *    wish to.  Caller must run wait_for_completion() on its own.
+ */
+int blkdev_issue_flush(struct block_device *bdev, sector_t *error_sector)
+{
+        DECLARE_COMPLETION_ONSTACK(wait);
+        struct request_queue *q;
+        struct bio *bio;
+        int ret;
+
+        if (bdev->bd_disk == NULL)
+                return -ENXIO;
+
+        q = bdev_get_queue(bdev);
+        if (!q)
+                return -ENXIO;
+
+        bio = bio_alloc(GFP_KERNEL, 0);
+        if (!bio)
+                return -ENOMEM;
+
+        bio->bi_end_io = bio_end_empty_barrier;
+        bio->bi_private = &wait;
+        bio->bi_bdev = bdev;
+        submit_bio(1 << BIO_RW_BARRIER, bio);
+
+        wait_for_completion(&wait);
+
+        /*
+         * The driver must store the error location in ->bi_sector, if
+         * it supports it. For non-stacked drivers, this should be copied
+         * from rq->sector.
+         */
+        if (error_sector)
+                *error_sector = bio->bi_sector;
+
+        ret = 0;
+        if (!bio_flagged(bio, BIO_UPTODATE))
+                ret = -EIO;
+
+        bio_put(bio);
+        return ret;
+}
+
+EXPORT_SYMBOL(blkdev_issue_flush);