drbd: REQ_HARDBARRIER -> REQ_FUA transition for meta data accesses

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>

drivers/block/drbd/drbd_actlog.c

@@ -78,11 +78,10 @@ static int _drbd_md_sync_page_io(struct drbd_conf *mdev,
 	init_completion(&md_io.event);
 	md_io.error = 0;
 
-	if ((rw & WRITE) && !test_bit(MD_NO_BARRIER, &mdev->flags))
-		rw |= REQ_HARDBARRIER;
+	if ((rw & WRITE) && !test_bit(MD_NO_FUA, &mdev->flags))
+		rw |= REQ_FUA;
 	rw |= REQ_UNPLUG | REQ_SYNC;
 
- retry:
 	bio = bio_alloc(GFP_NOIO, 1);
 	bio->bi_bdev = bdev->md_bdev;
 	bio->bi_sector = sector;
@@ -100,17 +99,6 @@ static int _drbd_md_sync_page_io(struct drbd_conf *mdev,
 	wait_for_completion(&md_io.event);
 	ok = bio_flagged(bio, BIO_UPTODATE) && md_io.error == 0;
 
-	/* check for unsupported barrier op.
-	 * would rather check on EOPNOTSUPP, but that is not reliable.
-	 * don't try again for ANY return value != 0 */
-	if (unlikely((bio->bi_rw & REQ_HARDBARRIER) && !ok)) {
-		/* Try again with no barrier */
-		dev_warn(DEV, "Barriers not supported on meta data device - disabling\n");
-		set_bit(MD_NO_BARRIER, &mdev->flags);
-		rw &= ~REQ_HARDBARRIER;
-		bio_put(bio);
-		goto retry;
-	}
  out:
 	bio_put(bio);
 	return ok;

drivers/block/drbd/drbd_int.h

@@ -835,8 +835,7 @@ enum {
 	NO_BARRIER_SUPP,	/* underlying block device doesn't implement barriers */
 	CONSIDER_RESYNC,
 
-	MD_NO_BARRIER,		/* meta data device does not support barriers,
-				   so don't even try */
+	MD_NO_FUA,		/* Users wants us to not use FUA/FLUSH on meta data dev */
 	SUSPEND_IO,		/* suspend application io */
 	BITMAP_IO,		/* suspend application io;
 				   once no more io in flight, start bitmap io */
@@ -2404,13 +2403,13 @@ static inline void drbd_md_flush(struct drbd_conf *mdev)
 {
 	int r;
 
-	if (test_bit(MD_NO_BARRIER, &mdev->flags))
+	if (test_bit(MD_NO_FUA, &mdev->flags))
 		return;
 
 	r = blkdev_issue_flush(mdev->ldev->md_bdev, GFP_KERNEL, NULL,
 			BLKDEV_IFL_WAIT);
 	if (r) {
-		set_bit(MD_NO_BARRIER, &mdev->flags);
+		set_bit(MD_NO_FUA, &mdev->flags);
 		dev_err(DEV, "meta data flush failed with status %d, disabling md-flushes\n", r);
 	}
 }

drivers/block/drbd/drbd_nl.c

@@ -1103,9 +1103,9 @@ static int drbd_nl_disk_conf(struct drbd_conf *mdev, struct drbd_nl_cfg_req *nlp
 	/* Reset the "barriers don't work" bits here, then force meta data to
 	 * be written, to ensure we determine if barriers are supported. */
 	if (nbc->dc.no_md_flush)
-		set_bit(MD_NO_BARRIER, &mdev->flags);
+		set_bit(MD_NO_FUA, &mdev->flags);
 	else
-		clear_bit(MD_NO_BARRIER, &mdev->flags);
+		clear_bit(MD_NO_FUA, &mdev->flags);
 
 	/* Point of no return reached.
 	 * Devices and memory are no longer released by error cleanup below.