f2fs: Prevent swap file in LFS mode

commit d927ccf upstream.

The kernel writes to swap files on f2fs directly without the assistance
of the filesystem. This direct write by kernel can be non-sequential
even when the f2fs is in LFS mode. Such non-sequential write conflicts
with the LFS semantics. Especially when f2fs is set up on zoned block
devices, the non-sequential write causes unaligned write command errors.

To avoid the non-sequential writes to swap files, prevent swap file
activation when the filesystem is in LFS mode.

Fixes: 4969c06 ("f2fs: support swap file w/ DIO")
Signed-off-by: Shin'ichiro Kawasaki <shinichiro.kawasaki@wdc.com>
Cc: stable@vger.kernel.org # v5.10+
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

fs/f2fs/data.c

@@ -4112,6 +4112,12 @@ static int f2fs_swap_activate(struct swap_info_struct *sis, struct file *file,
 	if (f2fs_readonly(F2FS_I_SB(inode)->sb))
 		return -EROFS;
 
+	if (f2fs_lfs_mode(F2FS_I_SB(inode))) {
+		f2fs_err(F2FS_I_SB(inode),
+			"Swapfile not supported in LFS mode");
+		return -EINVAL;
+	}
+
 	ret = f2fs_convert_inline_inode(inode);
 	if (ret)
 		return ret;