ext4: remove redundant S_ISREG() checks from ext4_fallocate()

ext4_fallocate() is only used in the file_operations for regular files.
Also, the VFS only allows fallocate() on regular files and block
devices, but block devices always use blkdev_fallocate().  For both of
these reasons, S_ISREG() is always true in ext4_fallocate().

Therefore the S_ISREG() checks in ext4_zero_range(),
ext4_collapse_range(), ext4_insert_range(), and ext4_punch_hole() are
redundant.  Remove them.
Signed-off-by: Eric Biggers <ebiggers@google.com>
Link: https://lore.kernel.org/r/20191231180444.46586-4-ebiggers@kernel.orgSigned-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

@@ -4674,9 +4674,6 @@ static long ext4_zero_range(struct file *file, loff_t offset,
 
 	trace_ext4_zero_range(inode, offset, len, mode);
 
-	if (!S_ISREG(inode->i_mode))
-		return -EINVAL;
-
 	/* Call ext4_force_commit to flush all data in case of data=journal. */
 	if (ext4_should_journal_data(inode)) {
 		ret = ext4_force_commit(inode->i_sb);
@@ -5439,9 +5436,6 @@ int ext4_collapse_range(struct inode *inode, loff_t offset, loff_t len)
 	if (!IS_ALIGNED(offset | len, EXT4_CLUSTER_SIZE(sb)))
 		return -EINVAL;
 
-	if (!S_ISREG(inode->i_mode))
-		return -EINVAL;
-
 	trace_ext4_collapse_range(inode, offset, len);
 
 	punch_start = offset >> EXT4_BLOCK_SIZE_BITS(sb);
@@ -5588,9 +5582,6 @@ int ext4_insert_range(struct inode *inode, loff_t offset, loff_t len)
 	if (!IS_ALIGNED(offset | len, EXT4_CLUSTER_SIZE(sb)))
 		return -EINVAL;
 
-	if (!S_ISREG(inode->i_mode))
-		return -EOPNOTSUPP;
-
 	trace_ext4_insert_range(inode, offset, len);
 
 	offset_lblk = offset >> EXT4_BLOCK_SIZE_BITS(sb);

fs/ext4/inode.c

@@ -3940,9 +3940,6 @@ int ext4_punch_hole(struct inode *inode, loff_t offset, loff_t length)
 	unsigned int credits;
 	int ret = 0;
 
-	if (!S_ISREG(inode->i_mode))
-		return -EOPNOTSUPP;
-
 	trace_ext4_punch_hole(inode, offset, length, 0);
 
 	ext4_clear_inode_state(inode, EXT4_STATE_MAY_INLINE_DATA);