btrfs: add helper to clear EXTENT_BUFFER_READING

We are clearing the bit and waking up any waiters in two different
places.  Factor that code out into a static helper function.
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Tavian Barnes <tavianator@tavianator.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/extent_io.c

@@ -4260,6 +4260,13 @@ void set_extent_buffer_uptodate(struct extent_buffer *eb)
 	}
 }
 
+static void clear_extent_buffer_reading(struct extent_buffer *eb)
+{
+	clear_bit(EXTENT_BUFFER_READING, &eb->bflags);
+	smp_mb__after_atomic();
+	wake_up_bit(&eb->bflags, EXTENT_BUFFER_READING);
+}
+
 static void end_bbio_meta_read(struct btrfs_bio *bbio)
 {
 	struct extent_buffer *eb = bbio->private;
@@ -4294,9 +4301,7 @@ static void end_bbio_meta_read(struct btrfs_bio *bbio)
 		bio_offset += len;
 	}
 
-	clear_bit(EXTENT_BUFFER_READING, &eb->bflags);
-	smp_mb__after_atomic();
-	wake_up_bit(&eb->bflags, EXTENT_BUFFER_READING);
+	clear_extent_buffer_reading(eb);
 	free_extent_buffer(eb);
 
 	bio_put(&bbio->bio);
@@ -4330,9 +4335,7 @@ int read_extent_buffer_pages(struct extent_buffer *eb, int wait, int mirror_num,
 	 * will now be set, and we shouldn't read it in again.
 	 */
 	if (unlikely(test_bit(EXTENT_BUFFER_UPTODATE, &eb->bflags))) {
-		clear_bit(EXTENT_BUFFER_READING, &eb->bflags);
-		smp_mb__after_atomic();
-		wake_up_bit(&eb->bflags, EXTENT_BUFFER_READING);
+		clear_extent_buffer_reading(eb);
 		return 0;
 	}