block: get rid of the WRITE_ODIRECT flag

Hi,

The WRITE_ODIRECT flag is only used in one place, and that code path
happens to also call blk_run_address_space.  The introduction of this
flag, then, could result in the device being unplugged twice for every
I/O.

Further, with the batching changes in the next patch, we don't want an
O_DIRECT write to imply a queue unplug.

Signed-off-by: Jeff Moyer <jmoyer@redhat.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/fs/direct-io.c b/fs/direct-io.c
index 8b10b87..c86d35f 100644
--- a/fs/direct-io.c
+++ b/fs/direct-io.c
@@ -1124,7 +1124,7 @@
 	int acquire_i_mutex = 0;
 
 	if (rw & WRITE)
-		rw = WRITE_ODIRECT;
+		rw = WRITE_SYNC_PLUG;
 
 	if (bdev)
 		bdev_blkbits = blksize_bits(bdev_logical_block_size(bdev));