block: deprecate barrier and replace blk_queue_ordered() with blk_queue_flush()

Barrier is deemed too heavy and will soon be replaced by FLUSH/FUA
requests.  Deprecate barrier.  All REQ_HARDBARRIERs are failed with
-EOPNOTSUPP and blk_queue_ordered() is replaced with simpler
blk_queue_flush().

blk_queue_flush() takes combinations of REQ_FLUSH and FUA.  If a
device has write cache and can flush it, it should set REQ_FLUSH.  If
the device can handle FUA writes, it should also set REQ_FUA.

All blk_queue_ordered() users are converted.

* ORDERED_DRAIN is mapped to 0 which is the default value.
* ORDERED_DRAIN_FLUSH is mapped to REQ_FLUSH.
* ORDERED_DRAIN_FLUSH_FUA is mapped to REQ_FLUSH | REQ_FUA.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Boaz Harrosh <bharrosh@panasas.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Nick Piggin <npiggin@kernel.dk>
Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Jeremy Fitzhardinge <jeremy@xensource.com>
Cc: Chris Wright <chrisw@sous-sol.org>
Cc: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Cc: Geert Uytterhoeven <Geert.Uytterhoeven@sonycom.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Alasdair G Kergon <agk@redhat.com>
Cc: Pierre Ossman <drzeus@drzeus.cx>
Cc: Stefan Weinhuber <wein@de.ibm.com>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>

15 files changed, 67 insertions, 102 deletions

diff --git a/block/blk-barrier.c b/block/blk-barrier.c
index c807e9ca3a68..ed0aba5463ab 100644
--- a/block/blk-barrier.c
+++ b/block/blk-barrier.c
@@ -9,35 +9,6 @@
 
 #include "blk.h"
 
-/**
- * blk_queue_ordered - does this queue support ordered writes
- * @q:        the request queue
- * @ordered:  one of QUEUE_ORDERED_*
- *
- * 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)
-{
-        if (ordered != QUEUE_ORDERED_NONE &&
-            ordered != QUEUE_ORDERED_DRAIN &&
-            ordered != QUEUE_ORDERED_DRAIN_FLUSH &&
-            ordered != QUEUE_ORDERED_DRAIN_FUA) {
-                printk(KERN_ERR "blk_queue_ordered: bad value %d\n", ordered);
-                return -EINVAL;
-        }
-
-        q->ordered = ordered;
-        q->next_ordered = ordered;
-
-        return 0;
-}
-EXPORT_SYMBOL(blk_queue_ordered);
-
 /*
  * Cache flushing for ordered writes handling
  */
diff --git a/block/blk-core.c b/block/blk-core.c
index ee1a1e7e63cc..f06354183b29 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -1203,11 +1203,13 @@ static int __make_request(struct request_queue *q, struct bio *bio)
         const unsigned int ff = bio->bi_rw & REQ_FAILFAST_MASK;
         int rw_flags;
 
-        if ((bio->bi_rw & REQ_HARDBARRIER) &&
-            (q->next_ordered == QUEUE_ORDERED_NONE)) {
+        /* REQ_HARDBARRIER is no more */
+        if (WARN_ONCE(bio->bi_rw & REQ_HARDBARRIER,
+                "block: HARDBARRIER is deprecated, use FLUSH/FUA instead\n")) {
                 bio_endio(bio, -EOPNOTSUPP);
                 return 0;
         }
+
         /*
          * low level driver can indicate that it wants pages above a
          * certain limit bounced to low memory (ie for highmem, or even
diff --git a/block/blk-settings.c b/block/blk-settings.c
index a234f4bf1d6f..9b18afcfe925 100644
--- a/block/blk-settings.c
+++ b/block/blk-settings.c
@@ -794,6 +794,26 @@ void blk_queue_update_dma_alignment(struct request_queue *q, int mask)
 }
 EXPORT_SYMBOL(blk_queue_update_dma_alignment);
 
+/**
+ * blk_queue_flush - configure queue's cache flush capability
+ * @q:          the request queue for the device
+ * @flush:      0, REQ_FLUSH or REQ_FLUSH | REQ_FUA
+ *
+ * Tell block layer cache flush capability of @q.  If it supports
+ * flushing, REQ_FLUSH should be set.  If it supports bypassing
+ * write cache for individual writes, REQ_FUA should be set.
+ */
+void blk_queue_flush(struct request_queue *q, unsigned int flush)
+{
+        WARN_ON_ONCE(flush & ~(REQ_FLUSH | REQ_FUA));
+
+        if (WARN_ON_ONCE(!(flush & REQ_FLUSH) && (flush & REQ_FUA)))
+                flush &= ~REQ_FUA;
+
+        q->flush_flags = flush & (REQ_FLUSH | REQ_FUA);
+}
+EXPORT_SYMBOL_GPL(blk_queue_flush);
+
 static int __init blk_settings_init(void)
 {
         blk_max_low_pfn = max_low_pfn - 1;
diff --git a/drivers/block/brd.c b/drivers/block/brd.c
index 47a41272d26b..fa33f97722ba 100644
--- a/drivers/block/brd.c
+++ b/drivers/block/brd.c
@@ -482,7 +482,6 @@ static struct brd_device *brd_alloc(int i)
         if (!brd->brd_queue)
                 goto out_free_dev;
         blk_queue_make_request(brd->brd_queue, brd_make_request);
-        blk_queue_ordered(brd->brd_queue, QUEUE_ORDERED_DRAIN);
         blk_queue_max_hw_sectors(brd->brd_queue, 1024);
         blk_queue_bounce_limit(brd->brd_queue, BLK_BOUNCE_ANY);
 
diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index c3a4a2e176da..953d1e12f4d4 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -832,7 +832,7 @@ static int loop_set_fd(struct loop_device *lo, fmode_t mode,
         lo->lo_queue->unplug_fn = loop_unplug;
 
         if (!(lo_flags & LO_FLAGS_READ_ONLY) && file->f_op->fsync)
-                blk_queue_ordered(lo->lo_queue, QUEUE_ORDERED_DRAIN_FLUSH);
+                blk_queue_flush(lo->lo_queue, REQ_FLUSH);
 
         set_capacity(lo->lo_disk, size);
         bd_set_size(bdev, size << 9);
diff --git a/drivers/block/osdblk.c b/drivers/block/osdblk.c
index 2284b4f05c62..72d62462433d 100644
--- a/drivers/block/osdblk.c
+++ b/drivers/block/osdblk.c
@@ -439,7 +439,7 @@ static int osdblk_init_disk(struct osdblk_device *osdev)
         blk_queue_stack_limits(q, osd_request_queue(osdev->osd));
 
         blk_queue_prep_rq(q, blk_queue_start_tag);
-        blk_queue_ordered(q, QUEUE_ORDERED_DRAIN_FLUSH);
+        blk_queue_flush(q, REQ_FLUSH);
 
         disk->queue = q;
 
diff --git a/drivers/block/ps3disk.c b/drivers/block/ps3disk.c
index e9da874d0419..4911f9e57bc7 100644
--- a/drivers/block/ps3disk.c
+++ b/drivers/block/ps3disk.c
@@ -468,7 +468,7 @@ static int __devinit ps3disk_probe(struct ps3_system_bus_device *_dev)
         blk_queue_dma_alignment(queue, dev->blk_size-1);
         blk_queue_logical_block_size(queue, dev->blk_size);
 
-        blk_queue_ordered(queue, QUEUE_ORDERED_DRAIN_FLUSH);
+        blk_queue_flush(queue, REQ_FLUSH);
 
         blk_queue_max_segments(queue, -1);
         blk_queue_max_segment_size(queue, dev->bounce_size);
diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
index 79652809eee8..d10b635b3946 100644
--- a/drivers/block/virtio_blk.c
+++ b/drivers/block/virtio_blk.c
@@ -388,22 +388,15 @@ static int __devinit virtblk_probe(struct virtio_device *vdev)
         vblk->disk->driverfs_dev = &vdev->dev;
         index++;
 
-        if (virtio_has_feature(vdev, VIRTIO_BLK_F_FLUSH)) {
-                /*
-                 * If the FLUSH feature is supported we do have support for
-                 * flushing a volatile write cache on the host.  Use that
-                 * to implement write barrier support.
-                 */
-                blk_queue_ordered(q, QUEUE_ORDERED_DRAIN_FLUSH);
-        } else {
-                /*
-                 * If the FLUSH feature is not supported we must assume that
-                 * the host does not perform any kind of volatile write
-                 * caching. We still need to drain the queue to provider
-                 * proper barrier semantics.
-                 */
-                blk_queue_ordered(q, QUEUE_ORDERED_DRAIN);
-        }
+        /*
+         * If the FLUSH feature is supported we do have support for
+         * flushing a volatile write cache on the host.  Use that to
+         * implement write barrier support; otherwise, we must assume
+         * that the host does not perform any kind of volatile write
+         * caching.
+         */
+        if (virtio_has_feature(vdev, VIRTIO_BLK_F_FLUSH))
+                blk_queue_flush(q, REQ_FLUSH);
 
         /* If disk is read-only in the host, the guest should obey */
         if (virtio_has_feature(vdev, VIRTIO_BLK_F_RO))
diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
index 50ec6f834996..0b1eea643262 100644
--- a/drivers/block/xen-blkfront.c
+++ b/drivers/block/xen-blkfront.c
@@ -95,7 +95,7 @@ struct blkfront_info
         struct gnttab_free_callback callback;
         struct blk_shadow shadow[BLK_RING_SIZE];
         unsigned long shadow_free;
-        int feature_barrier;
+        unsigned int feature_flush;
         int is_ready;
 };
 
@@ -418,25 +418,12 @@ static int xlvbd_init_blk_queue(struct gendisk *gd, u16 sector_size)
 }
 
 
-static int xlvbd_barrier(struct blkfront_info *info)
+static void xlvbd_flush(struct blkfront_info *info)
 {
-        int err;
-        const char *barrier;
-
-        switch (info->feature_barrier) {
-        case QUEUE_ORDERED_DRAIN:       barrier = "enabled"; break;
-        case QUEUE_ORDERED_NONE:        barrier = "disabled"; break;
-        default:                        return -EINVAL;
-        }
-
-        err = blk_queue_ordered(info->rq, info->feature_barrier);
-
-        if (err)
-                return err;
-
+        blk_queue_flush(info->rq, info->feature_flush);
         printk(KERN_INFO "blkfront: %s: barriers %s\n",
-               info->gd->disk_name, barrier);
-        return 0;
+               info->gd->disk_name,
+               info->feature_flush ? "enabled" : "disabled");
 }
 
 
@@ -515,7 +502,7 @@ static int xlvbd_alloc_gendisk(blkif_sector_t capacity,
         info->rq = gd->queue;
         info->gd = gd;
 
-        xlvbd_barrier(info);
+        xlvbd_flush(info);
 
         if (vdisk_info & VDISK_READONLY)
                 set_disk_ro(gd, 1);
@@ -661,8 +648,8 @@ static irqreturn_t blkif_interrupt(int irq, void *dev_id)
                                 printk(KERN_WARNING "blkfront: %s: write barrier op failed\n",
                                        info->gd->disk_name);
                                 error = -EOPNOTSUPP;
-                                info->feature_barrier = QUEUE_ORDERED_NONE;
-                                xlvbd_barrier(info);
+                                info->feature_flush = 0;
+                                xlvbd_flush(info);
                         }
                         /* fall through */
                 case BLKIF_OP_READ:
@@ -1075,19 +1062,13 @@ static void blkfront_connect(struct blkfront_info *info)
         /*
          * If there's no "feature-barrier" defined, then it means
          * we're dealing with a very old backend which writes
-         * synchronously; draining will do what needs to get done.
+         * synchronously; nothing to do.
          *
          * If there are barriers, then we use flush.
-         *
-         * If barriers are not supported, then there's no much we can
-         * do, so just set ordering to NONE.
          */
-        if (err)
-                info->feature_barrier = QUEUE_ORDERED_DRAIN;
-        else if (barrier)
-                info->feature_barrier = QUEUE_ORDERED_DRAIN_FLUSH;
-        else
-                info->feature_barrier = QUEUE_ORDERED_NONE;
+        info->feature_flush = 0;
+        if (!err && barrier)
+                info->feature_flush = REQ_FLUSH;
 
         err = xlvbd_alloc_gendisk(sectors, info, binfo, sector_size);
         if (err) {
diff --git a/drivers/ide/ide-disk.c b/drivers/ide/ide-disk.c
index 7433e07de30e..7c5b01ce51d2 100644
--- a/drivers/ide/ide-disk.c
+++ b/drivers/ide/ide-disk.c
@@ -516,10 +516,10 @@ static int ide_do_setfeature(ide_drive_t *drive, u8 feature, u8 nsect)
         return ide_no_data_taskfile(drive, &cmd);
 }
 
-static void update_ordered(ide_drive_t *drive)
+static void update_flush(ide_drive_t *drive)
 {
         u16 *id = drive->id;
-        unsigned ordered = QUEUE_ORDERED_NONE;
+        unsigned flush = 0;
 
         if (drive->dev_flags & IDE_DFLAG_WCACHE) {
                 unsigned long long capacity;
@@ -543,13 +543,12 @@ static void update_ordered(ide_drive_t *drive)
                        drive->name, barrier ? "" : "not ");
 
                 if (barrier) {
-                        ordered = QUEUE_ORDERED_DRAIN_FLUSH;
+                        flush = REQ_FLUSH;
                         blk_queue_prep_rq(drive->queue, idedisk_prep_fn);
                 }
-        } else
-                ordered = QUEUE_ORDERED_DRAIN;
+        }
 
-        blk_queue_ordered(drive->queue, ordered);
+        blk_queue_flush(drive->queue, flush);
 }
 
 ide_devset_get_flag(wcache, IDE_DFLAG_WCACHE);
@@ -572,7 +571,7 @@ static int set_wcache(ide_drive_t *drive, int arg)
                 }
         }
 
-        update_ordered(drive);
+        update_flush(drive);
 
         return err;
 }
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index ac384b2a6a33..b1d92be8f990 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -2245,7 +2245,7 @@ static int dm_init_request_based_queue(struct mapped_device *md)
         blk_queue_softirq_done(md->queue, dm_softirq_done);
         blk_queue_prep_rq(md->queue, dm_prep_fn);
         blk_queue_lld_busy(md->queue, dm_lld_busy);
-        blk_queue_ordered(md->queue, QUEUE_ORDERED_DRAIN_FLUSH);
+        blk_queue_flush(md->queue, REQ_FLUSH);
 
         elv_register_queue(md->queue);
 
diff --git a/drivers/mmc/card/queue.c b/drivers/mmc/card/queue.c
index e876678176be..9c0b42bfe089 100644
--- a/drivers/mmc/card/queue.c
+++ b/drivers/mmc/card/queue.c
@@ -128,7 +128,6 @@ int mmc_init_queue(struct mmc_queue *mq, struct mmc_card *card, spinlock_t *lock
         mq->req = NULL;
 
         blk_queue_prep_rq(mq->queue, mmc_prep_request);
-        blk_queue_ordered(mq->queue, QUEUE_ORDERED_DRAIN);
         queue_flag_set_unlocked(QUEUE_FLAG_NONROT, mq->queue);
         if (mmc_can_erase(card)) {
                 queue_flag_set_unlocked(QUEUE_FLAG_DISCARD, mq->queue);
diff --git a/drivers/s390/block/dasd.c b/drivers/s390/block/dasd.c
index 8373ca0de8e0..9b106d83b0cd 100644
--- a/drivers/s390/block/dasd.c
+++ b/drivers/s390/block/dasd.c
@@ -2197,7 +2197,6 @@ static void dasd_setup_queue(struct dasd_block *block)
          */
         blk_queue_max_segment_size(block->request_queue, PAGE_SIZE);
         blk_queue_segment_boundary(block->request_queue, PAGE_SIZE - 1);
-        blk_queue_ordered(block->request_queue, QUEUE_ORDERED_DRAIN);
 }
 
 /*
diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index cdfc51ab9cf2..63bd01ae534f 100644
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -2109,7 +2109,7 @@ static int sd_revalidate_disk(struct gendisk *disk)
         struct scsi_disk *sdkp = scsi_disk(disk);
         struct scsi_device *sdp = sdkp->device;
         unsigned char *buffer;
-        unsigned ordered;
+        unsigned flush = 0;
 
         SCSI_LOG_HLQUEUE(3, sd_printk(KERN_INFO, sdkp,
                                       "sd_revalidate_disk\n"));
@@ -2151,15 +2151,15 @@ static int sd_revalidate_disk(struct gendisk *disk)
 
         /*
          * We now have all cache related info, determine how we deal
-         * with ordered requests.
+         * with flush requests.
          */
-        if (sdkp->WCE)
-                ordered = sdkp->DPOFUA
-                        ? QUEUE_ORDERED_DRAIN_FUA : QUEUE_ORDERED_DRAIN_FLUSH;
-        else
-                ordered = QUEUE_ORDERED_DRAIN;
+        if (sdkp->WCE) {
+                flush |= REQ_FLUSH;
+                if (sdkp->DPOFUA)
+                        flush |= REQ_FUA;
+        }
 
-        blk_queue_ordered(sdkp->disk->queue, ordered);
+        blk_queue_flush(sdkp->disk->queue, flush);
 
         set_capacity(disk, sdkp->capacity);
         kfree(buffer);
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 7077bc0d6138..e97911d4dec3 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -355,8 +355,10 @@ struct request_queue
         struct blk_trace        *blk_trace;
 #endif
         /*
-         * reserved for flush operations
+         * for flush operations
          */
+        unsigned int            flush_flags;
+
         unsigned int            ordered, next_ordered, ordseq;
         int                     orderr, ordcolor;
         struct request          pre_flush_rq, bar_rq, post_flush_rq;
@@ -865,8 +867,8 @@ extern void blk_queue_update_dma_alignment(struct request_queue *, int);
 extern void blk_queue_softirq_done(struct request_queue *, softirq_done_fn *);
 extern void blk_queue_rq_timed_out(struct request_queue *, rq_timed_out_fn *);
 extern void blk_queue_rq_timeout(struct request_queue *, unsigned int);
+extern void blk_queue_flush(struct request_queue *q, unsigned int flush);
 extern struct backing_dev_info *blk_get_backing_dev_info(struct block_device *bdev);
-extern int blk_queue_ordered(struct request_queue *, unsigned);
 extern bool blk_do_ordered(struct request_queue *, struct request **);
 extern unsigned blk_ordered_cur_seq(struct request_queue *);
 extern unsigned blk_ordered_req_seq(struct request *);