Merge branch 'for-2.6.37/barrier' of git://git.kernel.dk/linux-2.6-block

* 'for-2.6.37/barrier' of git://git.kernel.dk/linux-2.6-block: (46 commits)
  xen-blkfront: disable barrier/flush write support
  Added blk-lib.c and blk-barrier.c was renamed to blk-flush.c
  block: remove BLKDEV_IFL_WAIT
  aic7xxx_old: removed unused 'req' variable
  block: remove the BH_Eopnotsupp flag
  block: remove the BLKDEV_IFL_BARRIER flag
  block: remove the WRITE_BARRIER flag
  swap: do not send discards as barriers
  fat: do not send discards as barriers
  ext4: do not send discards as barriers
  jbd2: replace barriers with explicit flush / FUA usage
  jbd2: Modify ASYNC_COMMIT code to not rely on queue draining on barrier
  jbd: replace barriers with explicit flush / FUA usage
  nilfs2: replace barriers with explicit flush / FUA usage
  reiserfs: replace barriers with explicit flush / FUA usage
  gfs2: replace barriers with explicit flush / FUA usage
  btrfs: replace barriers with explicit flush / FUA usage
  xfs: replace barriers with explicit flush / FUA usage
  block: pass gfp_mask and flags to sb_issue_discard
  dm: convey that all flushes are processed as empty
  ...

1 files changed, 9 insertions, 20 deletions

diff --git a/Documentation/lguest/lguest.c b/Documentation/lguest/lguest.c
index 8a6a8c6d498..dc73bc54cc4 100644
--- a/Documentation/lguest/lguest.c
+++ b/Documentation/lguest/lguest.c
@@ -1640,15 +1640,6 @@ static void blk_request(struct virtqueue *vq)
         off = out->sector * 512;
 
         /*
-         * The block device implements "barriers", where the Guest indicates
-         * that it wants all previous writes to occur before this write.  We
-         * don't have a way of asking our kernel to do a barrier, so we just
-         * synchronize all the data in the file.  Pretty poor, no?
-         */
-        if (out->type & VIRTIO_BLK_T_BARRIER)
-                fdatasync(vblk->fd);
-
-        /*
          * In general the virtio block driver is allowed to try SCSI commands.
          * It'd be nice if we supported eject, for example, but we don't.
          */
@@ -1680,6 +1671,13 @@ static void blk_request(struct virtqueue *vq)
                         /* Die, bad Guest, die. */
                         errx(1, "Write past end %llu+%u", off, ret);
                 }
+
+                wlen = sizeof(*in);
+                *in = (ret >= 0 ? VIRTIO_BLK_S_OK : VIRTIO_BLK_S_IOERR);
+        } else if (out->type & VIRTIO_BLK_T_FLUSH) {
+                /* Flush */
+                ret = fdatasync(vblk->fd);
+                verbose("FLUSH fdatasync: %i\n", ret);
                 wlen = sizeof(*in);
                 *in = (ret >= 0 ? VIRTIO_BLK_S_OK : VIRTIO_BLK_S_IOERR);
         } else {
@@ -1703,15 +1701,6 @@ static void blk_request(struct virtqueue *vq)
                 }
         }
 
-        /*
-         * OK, so we noted that it was pretty poor to use an fdatasync as a
-         * barrier.  But Christoph Hellwig points out that we need a sync
-         * *afterwards* as well: "Barriers specify no reordering to the front
-         * or the back."  And Jens Axboe confirmed it, so here we are:
-         */
-        if (out->type & VIRTIO_BLK_T_BARRIER)
-                fdatasync(vblk->fd);
-
         /* Finished that request. */
         add_used(vq, head, wlen);
 }
@@ -1736,8 +1725,8 @@ static void setup_block_file(const char *filename)
         vblk->fd = open_or_die(filename, O_RDWR|O_LARGEFILE);
         vblk->len = lseek64(vblk->fd, 0, SEEK_END);
 
-        /* We support barriers. */
-        add_feature(dev, VIRTIO_BLK_F_BARRIER);
+        /* We support FLUSH. */
+        add_feature(dev, VIRTIO_BLK_F_FLUSH);
 
         /* Tell Guest how many sectors this device has. */
         conf.capacity = cpu_to_le64(vblk->len / 512);