block, drivers, fs: rename REQ_FLUSH to REQ_PREFLUSH

To avoid confusion between REQ_OP_FLUSH, which is handled by
request_fn drivers, and upper layers requesting the block layer
perform a flush sequence along with possibly a WRITE, this patch
renames REQ_FLUSH to REQ_PREFLUSH.

Signed-off-by: Mike Christie <mchristi@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index fcc68c8..aba7ed9 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -1003,12 +1003,12 @@
 		if (io_error == DM_ENDIO_REQUEUE)
 			return;
 
-		if ((bio->bi_rw & REQ_FLUSH) && bio->bi_iter.bi_size) {
+		if ((bio->bi_rw & REQ_PREFLUSH) && bio->bi_iter.bi_size) {
 			/*
 			 * Preflush done for flush with data, reissue
-			 * without REQ_FLUSH.
+			 * without REQ_PREFLUSH.
 			 */
-			bio->bi_rw &= ~REQ_FLUSH;
+			bio->bi_rw &= ~REQ_PREFLUSH;
 			queue_io(md, bio);
 		} else {
 			/* done with normal IO or empty flush */
@@ -1477,7 +1477,7 @@
 
 /*
  * A target may call dm_accept_partial_bio only from the map routine.  It is
- * allowed for all bio types except REQ_FLUSH.
+ * allowed for all bio types except REQ_PREFLUSH.
  *
  * dm_accept_partial_bio informs the dm that the target only wants to process
  * additional n_sectors sectors of the bio and the rest of the data should be
@@ -1507,7 +1507,7 @@
 {
 	struct dm_target_io *tio = container_of(bio, struct dm_target_io, clone);
 	unsigned bi_size = bio->bi_iter.bi_size >> SECTOR_SHIFT;
-	BUG_ON(bio->bi_rw & REQ_FLUSH);
+	BUG_ON(bio->bi_rw & REQ_PREFLUSH);
 	BUG_ON(bi_size > *tio->len_ptr);
 	BUG_ON(n_sectors > bi_size);
 	*tio->len_ptr -= bi_size - n_sectors;
@@ -1795,7 +1795,7 @@
 
 	start_io_acct(ci.io);
 
-	if (bio->bi_rw & REQ_FLUSH) {
+	if (bio->bi_rw & REQ_PREFLUSH) {
 		ci.bio = &ci.md->flush_bio;
 		ci.sector_count = 0;
 		error = __send_empty_flush(&ci);