lguest: replace VIRTIO_F_BARRIER support with VIRTIO_F_FLUSH support

VIRTIO_F_BARRIER is deprecated.  Replace it with VIRTIO_F_FLUSH
support.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>

1 files changed, 9 insertions, 20 deletions

diff --git a/Documentation/lguest/lguest.c b/Documentation/lguest/lguest.c
index e9ce3c554514..fbc64b331436 100644
--- a/Documentation/lguest/lguest.c
+++ b/Documentation/lguest/lguest.c
@@ -1639,15 +1639,6 @@ 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.
          */
@@ -1679,6 +1670,13 @@ 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 {
@@ -1702,15 +1700,6 @@ 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);
 }
@@ -1735,8 +1724,8 @@ 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);