ext4: remove obsolete comment from ext4_can_extents_be_merged()

Support for unwritten extents was added to ext4 a long time ago, so
remove a misleading comment that says they're a future feature.

Signed-off-by: Eric Biggers <ebiggers@google.com>
Link: https://lore.kernel.org/r/20191231180444.46586-7-ebiggers@kernel.org
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Reviewed-by: Ritesh Harjani <riteshh@linux.ibm.com>
Reviewed-by: Jan Kara <jack@suse.cz>

fs/ext4/extents.c

@@ -1716,11 +1716,6 @@ static int ext4_can_extents_be_merged(struct inode *inode,
 			le32_to_cpu(ex2->ee_block))
 		return 0;
 
-	/*
-	 * To allow future support for preallocated extents to be added
-	 * as an RO_COMPAT feature, refuse to merge to extents if
-	 * this can result in the top bit of ee_len being set.
-	 */
 	if (ext1_ee_len + ext2_ee_len > EXT_INIT_MAX_LEN)
 		return 0;