[PATCH v2 3/4] fs: ext4: support relative path for `journal_path` in mount option.

[Hongbo Li <lihongbo22@huawei.com>]

After `fs_param_is_blockdev` is implemented(in fs: add blockdev parser
for filesystem mount option.), `journal_devnum` can be obtained from
`result.uint_32` directly.

Additionally, the `fs_lookup_param` did not consider the relative path
for block device. When we mount ext4 with `journal_path` option using
relative path, `param->dirfd` was not set which will cause mounting
error.

This can be reproduced easily like this:

mke2fs -F -O journal_dev $JOURNAL_DEV -b 4096 100M
mkfs.ext4 -F -J device=$JOURNAL_DEV -b 4096 $FS_DEV
cd /dev; mount -t ext4 -o journal_path=`basename $JOURNAL_DEV` $FS_DEV $MNT

Fixes: 461c3af045d3 ("ext4: Change handle_mount_opt() to use fs_parameter")
Signed-off-by: Hongbo Li <lihongbo22@huawei.com>
---
 fs/ext4/super.c | 26 +-------------------------
 1 file changed, 1 insertion(+), 25 deletions(-)

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index c682fb927b64..94b39bcae99d 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -2290,39 +2290,15 @@ static int ext4_parse_param(struct fs_context *fc, struct fs_parameter *param)
 		ctx->spec |= EXT4_SPEC_s_resgid;
 		return 0;
 	case Opt_journal_dev:
-		if (is_remount) {
-			ext4_msg(NULL, KERN_ERR,
-				 "Cannot specify journal on remount");
-			return -EINVAL;
-		}
-		ctx->journal_devnum = result.uint_32;
-		ctx->spec |= EXT4_SPEC_JOURNAL_DEV;
-		return 0;
 	case Opt_journal_path:
-	{
-		struct inode *journal_inode;
-		struct path path;
-		int error;
-
 		if (is_remount) {
 			ext4_msg(NULL, KERN_ERR,
 				 "Cannot specify journal on remount");
 			return -EINVAL;
 		}
-
-		error = fs_lookup_param(fc, param, 1, LOOKUP_FOLLOW, &path);
-		if (error) {
-			ext4_msg(NULL, KERN_ERR, "error: could not find "
-				 "journal device path");
-			return -EINVAL;
-		}
-
-		journal_inode = d_inode(path.dentry);
-		ctx->journal_devnum = new_encode_dev(journal_inode->i_rdev);
+		ctx->journal_devnum = result.uint_32;
 		ctx->spec |= EXT4_SPEC_JOURNAL_DEV;
-		path_put(&path);
 		return 0;
-	}
 	case Opt_journal_ioprio:
 		if (result.uint_32 > 7) {
 			ext4_msg(NULL, KERN_ERR, "Invalid journal IO priority"
-- 
2.34.1