--- /dev/null
+/*
+ * Functions to sequence FLUSH and FUA writes.
+ */
+#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 {
+ QUEUE_FSEQ_STARTED = (1 << 0), /* flushing in progress */
+ QUEUE_FSEQ_PREFLUSH = (1 << 1), /* pre-flushing in progress */
+ QUEUE_FSEQ_DATA = (1 << 2), /* data write in progress */
+ QUEUE_FSEQ_POSTFLUSH = (1 << 3), /* post-flushing in progress */
+ QUEUE_FSEQ_DONE = (1 << 4),
+};
+
+static struct request *queue_next_fseq(struct request_queue *q);
+
+unsigned blk_flush_cur_seq(struct request_queue *q)
+{
+ if (!q->flush_seq)
+ return 0;
+ return 1 << ffz(q->flush_seq);
+}
+
+static struct request *blk_flush_complete_seq(struct request_queue *q,
+ unsigned seq, int error)
+{
+ struct request *next_rq = NULL;
+
+ if (error && !q->flush_err)
+ q->flush_err = error;
+
+ BUG_ON(q->flush_seq & seq);
+ q->flush_seq |= seq;
+
+ if (blk_flush_cur_seq(q) != QUEUE_FSEQ_DONE) {
+ /* not complete yet, queue the next flush sequence */
+ next_rq = queue_next_fseq(q);
+ } else {
+ /* complete this flush request */
+ __blk_end_request_all(q->orig_flush_rq, q->flush_err);
+ q->orig_flush_rq = NULL;
+ q->flush_seq = 0;
+
+ /* dispatch the next flush if there's one */
+ if (!list_empty(&q->pending_flushes)) {
+ next_rq = list_entry_rq(q->pending_flushes.next);
+ list_move(&next_rq->queuelist, &q->queue_head);
+ }
+ }
+ return next_rq;
+}
+
+static void blk_flush_complete_seq_end_io(struct request_queue *q,
+ unsigned seq, int error)
+{
+ bool was_empty = elv_queue_empty(q);
+ struct request *next_rq;
+
+ next_rq = blk_flush_complete_seq(q, seq, error);
+
+ /*
+ * Moving a request silently to empty queue_head may stall the
+ * queue. Kick the queue in those cases.
+ */
+ if (was_empty && next_rq)
+ __blk_run_queue(q);
+}
+
+static void pre_flush_end_io(struct request *rq, int error)
+{
+ elv_completed_request(rq->q, rq);
+ blk_flush_complete_seq_end_io(rq->q, QUEUE_FSEQ_PREFLUSH, error);
+}
+
+static void flush_data_end_io(struct request *rq, int error)
+{
+ elv_completed_request(rq->q, rq);
+ blk_flush_complete_seq_end_io(rq->q, QUEUE_FSEQ_DATA, error);
+}
+
+static void post_flush_end_io(struct request *rq, int error)
+{
+ elv_completed_request(rq->q, rq);
+ blk_flush_complete_seq_end_io(rq->q, QUEUE_FSEQ_POSTFLUSH, error);
+}
+
+static void init_flush_request(struct request *rq, struct gendisk *disk)
+{
+ rq->cmd_type = REQ_TYPE_FS;
+ rq->cmd_flags = WRITE_FLUSH;
+ rq->rq_disk = disk;
+}
+
+static struct request *queue_next_fseq(struct request_queue *q)
+{
+ struct request *orig_rq = q->orig_flush_rq;
+ struct request *rq = &q->flush_rq;
+
+ blk_rq_init(q, rq);
+
+ switch (blk_flush_cur_seq(q)) {
+ case QUEUE_FSEQ_PREFLUSH:
+ init_flush_request(rq, orig_rq->rq_disk);
+ rq->end_io = pre_flush_end_io;
+ break;
+ case QUEUE_FSEQ_DATA:
+ init_request_from_bio(rq, orig_rq->bio);
+ /*
+ * orig_rq->rq_disk may be different from
+ * bio->bi_bdev->bd_disk if orig_rq got here through
+ * remapping drivers. Make sure rq->rq_disk points
+ * to the same one as orig_rq.
+ */
+ rq->rq_disk = orig_rq->rq_disk;
+ rq->cmd_flags &= ~(REQ_FLUSH | REQ_FUA);
+ rq->cmd_flags |= orig_rq->cmd_flags & (REQ_FLUSH | REQ_FUA);
+ rq->end_io = flush_data_end_io;
+ break;
+ case QUEUE_FSEQ_POSTFLUSH:
+ init_flush_request(rq, orig_rq->rq_disk);
+ rq->end_io = post_flush_end_io;
+ break;
+ default:
+ BUG();
+ }
+
+ elv_insert(q, rq, ELEVATOR_INSERT_FRONT);
+ return rq;
+}
+
+struct request *blk_do_flush(struct request_queue *q, struct request *rq)
+{
+ unsigned int fflags = q->flush_flags; /* may change, cache it */
+ bool has_flush = fflags & REQ_FLUSH, has_fua = fflags & REQ_FUA;
+ bool do_preflush = has_flush && (rq->cmd_flags & REQ_FLUSH);
+ bool do_postflush = has_flush && !has_fua && (rq->cmd_flags & REQ_FUA);
+ unsigned skip = 0;
+
+ /*
+ * Special case. If there's data but flush is not necessary,
+ * the request can be issued directly.
+ *
+ * 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.
+ */
+ if (blk_rq_sectors(rq) && !do_preflush && !do_postflush) {
+ rq->cmd_flags &= ~REQ_FLUSH;
+ if (!has_fua)
+ rq->cmd_flags &= ~REQ_FUA;
+ return rq;
+ }
+
+ /*
+ * Sequenced flushes can't be processed in parallel. If
+ * another one is already in progress, queue for later
+ * processing.
+ */
+ if (q->flush_seq) {
+ list_move_tail(&rq->queuelist, &q->pending_flushes);
+ return NULL;
+ }
+
+ /*
+ * Start a new flush sequence
+ */
+ 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);
+}
+
+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);
projects / mv-sheeva.git / blobdiff