On 17.12.2021 18:02, Heiner Kallweit wrote:

On 17.12.2021 16:34, Heiner Kallweit wrote:

quoted

On 17.12.2021 16:24, Lukas Czerner wrote:

quoted

On Fri, Dec 17, 2021 at 04:11:32PM +0100, Heiner Kallweit wrote:

quoted

On linux-next systemd-remount-fs complains about an invalid mount option
here, resulting in a r/o root fs. After playing with the mount options
it turned out that data=ordered causes the problem. linux-next from Dec
1st was ok, so it seems to be related to the new mount API patches.

At a first glance I saw no obvious problem, the following looks good.
Maybe you have an idea where to look ..

static const struct constant_table ext4_param_data[] = {
	{"journal",	EXT4_MOUNT_JOURNAL_DATA},
	{"ordered",	EXT4_MOUNT_ORDERED_DATA},
	{"writeback",	EXT4_MOUNT_WRITEBACK_DATA},
	{}
};

	fsparam_enum	("data",		Opt_data, ext4_param_data),

Thank you for the report!

The ext4 mount has been reworked to use the new mount api and the work
has been applied to linux-next couple of days ago so I definitelly
assume there is a bug in there that I've missed. I will be looking into
it.

Can you be a little bit more specific about how to reproduce the problem
as well as the error it generates in the logs ? Any other mount options
used simultaneously, non-default file system features, or mount options
stored within the superblock ?

Can you reproduce it outside of the systemd unit, say a script ?

Yes:

[root@zotac ~]# mount -o remount,data=ordered /
mount: /: mount point not mounted or bad option.
[root@zotac ~]# mount -o remount,discard /
[root@zotac ~]#

"systemctl status systemd-remount-fs" shows the same error.

Following options I had in my fstab (ext4 fs):
rw,relatime,data=ordered,discard

No non-default system features.

quoted

Thanks!
-Lukas

Heiner

Sorry, should have looked at dmesg earlier. There I see:
EXT4-fs: Cannot change data mode on remount
Message seems to be triggered from ext4_check_opt_consistency().
Not sure why this error doesn't occur with old mount API.
And actually I don't change the data mode.

Based on the old API code: Maybe we need something like this?
At least it works for me.

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index b72d989b7..9ec7e526c 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c

@@ -2821,7 +2821,9 @@ static int ext4_check_opt_consistency(struct fs_context *fc,
                                 "Remounting file system with no journal "
                                 "so ignoring journalled data option");
                        ctx_clear_mount_opt(ctx, EXT4_MOUNT_DATA_FLAGS);
-               } else if (ctx->mask_s_mount_opt & EXT4_MOUNT_DATA_FLAGS) {
+               } else if (ctx->mask_s_mount_opt & EXT4_MOUNT_DATA_FLAGS &&
+                          (ctx->vals_s_mount_opt & EXT4_MOUNT_DATA_FLAGS) !=
+                          (sbi->s_mount_opt & EXT4_MOUNT_DATA_FLAGS)) {
                        ext4_msg(NULL, KERN_ERR, "Cannot change data mode "
                                 "on remount");
                        return -EINVAL;