ext4: convert to alloc_workqueue()

Convert create_workqueue() to alloc_workqueue().  This is an identity
conversion.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: "Theodore Ts'o" <tytso@mit.edu>
Cc: Andreas Dilger <adilger.kernel@dilger.ca>
Cc: linux-ext4@vger.kernel.org

fs/ext4/super.c

@@ -3507,7 +3507,12 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
 	percpu_counter_set(&sbi->s_dirtyblocks_counter, 0);
 
 no_journal:
-	EXT4_SB(sb)->dio_unwritten_wq = create_workqueue("ext4-dio-unwritten");
+	/*
+	 * The maximum number of concurrent works can be high and
+	 * concurrency isn't really necessary.  Limit it to 1.
+	 */
+	EXT4_SB(sb)->dio_unwritten_wq =
+		alloc_workqueue("ext4-dio-unwritten", WQ_MEM_RECLAIM, 1);
 	if (!EXT4_SB(sb)->dio_unwritten_wq) {
 		printk(KERN_ERR "EXT4-fs: failed to create DIO workqueue\n");
 		goto failed_mount_wq;