[PATCH] f2fs: allow empty strings for journaled quota options

[Hengyu Liang]

Commit 2a3db1e02ce0 ("f2fs: allow empty mount string for
Opt_usr|grp|projjquota") added support for passing usrjquota,
grpjquota and prjjquota as flags to disable journaled quotas.

However, it also replaced fsparam_string_empty() with fsparam_string(),
which rejects an empty string. As of now, mount(2) and
fsconfig(FSCONFIG_SET_STRING) reject usrjquota=, grpjquota= and
prjjquota= with EINVAL, although these forms are still documented in
Documentation/filesystems/f2fs.rst.

The issue can be reproduced on an F2FS device with:

    mount -t f2fs -o usrjquota= /dev/loop5 /mnt/f

Before this commit, the command succeeds. Afterwards, it fails with
EINVAL and logs "f2fs: Bad value for 'usrjquota'".
The same failure occurs when remounting to clear a quota file name.

This patch will restore fsparam_string_empty() for the three options
while retaining the flag entries, so both forms are accepted.

Fixes: 2a3db1e02ce0 ("f2fs: allow empty mount string for Opt_usr|grp|projjquota")
Cc: stable@xxxxxxxxxxxxxxx # 7.1+
Signed-off-by: Hengyu Liang <hengyul@xxxxxxxxxx>
---
 fs/f2fs/super.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
index 1314b6ccced9..3867094b25f6 100644
--- a/fs/f2fs/super.c
+++ b/fs/f2fs/super.c
@@ -338,11 +338,11 @@ static const struct fs_parameter_spec f2fs_param_specs[] = {
 	fsparam_flag("usrquota", Opt_usrquota),
 	fsparam_flag("grpquota", Opt_grpquota),
 	fsparam_flag("prjquota", Opt_prjquota),
-	fsparam_string("usrjquota", Opt_usrjquota),
+	fsparam_string_empty("usrjquota", Opt_usrjquota),
 	fsparam_flag("usrjquota", Opt_usrjquota),
-	fsparam_string("grpjquota", Opt_grpjquota),
+	fsparam_string_empty("grpjquota", Opt_grpjquota),
 	fsparam_flag("grpjquota", Opt_grpjquota),
-	fsparam_string("prjjquota", Opt_prjjquota),
+	fsparam_string_empty("prjjquota", Opt_prjjquota),
 	fsparam_flag("prjjquota", Opt_prjjquota),
 	fsparam_flag("nat_bits", Opt_nat_bits),
 	fsparam_enum("jqfmt", Opt_jqfmt, f2fs_param_jqfmt),
-- 
2.53.0