linux-ext4 - [PATCH v2] fs: ext4: support relative path for `journal

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Message-ID: <20240925015624.3817878-1-lihongbo22@huawei.com>
Date: Wed, 25 Sep 2024 09:56:24 +0800
From: Hongbo Li <lihongbo22@...wei.com>
To: <tytso@....edu>, <adilger.kernel@...ger.ca>, <viro@...iv.linux.org.uk>,
	<brauner@...nel.org>, <jack@...e.cz>
CC: <linux-ext4@...r.kernel.org>, <linux-fsdevel@...r.kernel.org>,
	<lihongbo22@...wei.com>, <chris.zjh@...wei.com>
Subject: [PATCH v2] fs: ext4: support relative path for `journal_path` in mount option.

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")
Suggested-by: Christian Brauner <brauner@...nel.org>
Signed-off-by: Hongbo Li <lihongbo22@...wei.com>
---
v2:
  - Change the journal_path parameter as string not bdev, and
    determine the relative path situation inside fs_lookup_param.
  - Add Suggested-by.

v1: https://lore.kernel.org/all/20240527-mahlen-packung-3fe035ab390d@brauner/
---
 fs/ext4/super.c | 4 ++--
 fs/fs_parser.c  | 3 +++
 2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 16a4ce704460..cd23536ce46e 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -1744,7 +1744,7 @@ static const struct fs_parameter_spec ext4_param_specs[] = {
 	fsparam_u32	("min_batch_time",	Opt_min_batch_time),
 	fsparam_u32	("max_batch_time",	Opt_max_batch_time),
 	fsparam_u32	("journal_dev",		Opt_journal_dev),
-	fsparam_bdev	("journal_path",	Opt_journal_path),
+	fsparam_string	("journal_path",	Opt_journal_path),
 	fsparam_flag	("journal_checksum",	Opt_journal_checksum),
 	fsparam_flag	("nojournal_checksum",	Opt_nojournal_checksum),
 	fsparam_flag	("journal_async_commit",Opt_journal_async_commit),
@@ -2301,7 +2301,7 @@ static int ext4_parse_param(struct fs_context *fc, struct fs_parameter *param)
 			return -EINVAL;
 		}
 
-		error = fs_lookup_param(fc, param, 1, LOOKUP_FOLLOW, &path);
+		error = fs_lookup_param(fc, param, true, LOOKUP_FOLLOW, &path);
 		if (error) {
 			ext4_msg(NULL, KERN_ERR, "error: could not find "
 				 "journal device path");
diff --git a/fs/fs_parser.c b/fs/fs_parser.c
index 24727ec34e5a..2ae296764b69 100644
--- a/fs/fs_parser.c
+++ b/fs/fs_parser.c
@@ -156,6 +156,9 @@ int fs_lookup_param(struct fs_context *fc,
 		f = getname_kernel(param->string);
 		if (IS_ERR(f))
 			return PTR_ERR(f);
+		/* for relative path */
+		if (f->name[0] != '/')
+			param->dirfd = AT_FDCWD;
 		put_f = true;
 		break;
 	case fs_value_is_filename:
-- 
2.34.1