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-rw-r--r--block/blk-barrier.c319
1 files changed, 319 insertions, 0 deletions
diff --git a/block/blk-barrier.c b/block/blk-barrier.c
new file mode 100644
index 00000000000..5f74fec327d
--- /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);