[PATCH] ubifs: Convert ubifs to use the new mount API

[Zhihao Cheng]

在 2024/9/27 4:36, Eric Sandeen 写道:
Hi Eric, two comments below.
> From: David Howells <dhowells at redhat.com>
> 
> Convert the ubifs filesystem to the new internal mount API as the old
> one will be obsoleted and removed.  This allows greater flexibility in
> communication of mount parameters between userspace, the VFS and the
> filesystem.
> 
> See Documentation/filesystems/mount_api.txt for more information.
> 
> Signed-off-by: David Howells <dhowells at redhat.com>
> [sandeen: forward-port old patch]
> Signed-off-by: Eric Sandeen <sandeen at redhat.com>
> cc: Richard Weinberger <richard at nod.at>
> cc: Zhihao Cheng <chengzhihao1 at huawei.com>
> cc: linux-mtd at lists.infradead.org
> ---
>   fs/ubifs/super.c | 459 +++++++++++++++++++++--------------------------
>   1 file changed, 204 insertions(+), 255 deletions(-)
> 
> diff --git a/fs/ubifs/super.c b/fs/ubifs/super.c
> index 291583005dd1..cf2e9104baff 100644
> --- a/fs/ubifs/super.c
> +++ b/fs/ubifs/super.c
[...]
> @@ -963,7 +963,7 @@ static int check_volume_empty(struct ubifs_info *c)
>    * Opt_no_bulk_read: disable bulk-reads
>    * Opt_chk_data_crc: check CRCs when reading data nodes
>    * Opt_no_chk_data_crc: do not check CRCs when reading data nodes
> - * Opt_override_compr: override default compressor
> + * Opt_compr: override default compressor
>    * Opt_assert: set ubifs_assert() action
>    * Opt_auth_key: The key name used for authentication
>    * Opt_auth_hash_name: The hash type used for authentication
> @@ -976,54 +976,46 @@ enum {
>   	Opt_no_bulk_read,
>   	Opt_chk_data_crc,
>   	Opt_no_chk_data_crc,
> -	Opt_override_compr,
> +	Opt_compr,

IMO, I prefer the old name 'Opt_override_compr', it looks more closer to 
the semantics. UBIFS already set the default compressor in 
'c->default_compr', the 'Opt_override_compr' is used to overwrite it.

[...]

> -static int ubifs_remount_fs(struct super_block *sb, int *flags, char *data)
> +static int ubifs_reconfigure(struct fs_context *fc)
>   {
> +	struct super_block *sb = fc->root->d_sb;
>   	int err;
>   	struct ubifs_info *c = sb->s_fs_info;
> +	struct ubifs_info *reconf = fc->s_fs_info;
>   
>   	sync_filesystem(sb);
> -	dbg_gen("old flags %#lx, new flags %#x", sb->s_flags, *flags);
> +	dbg_gen("old flags %#lx, new flags %#x", sb->s_flags, fc->sb_flags);
>   
> -	err = ubifs_parse_options(c, data, 1);
> -	if (err) {
> -		ubifs_err(c, "invalid or unknown remount parameter");
> -		return err;
> -	}
> +	/* Apply the mount option changes.
> +	 *
> +	 * [!] NOTE Replacing the auth_key_name and auth_hash_name is
> +	 *     very dodgy without locking.  Previously it just leaked
> +	 *     the old strings.  The strings only seem to be used
> +	 *     during mounting, so don't reconfigure those.
> +	 */
> +	c->mount_opts		= reconf->mount_opts;
> +	c->bulk_read		= reconf->bulk_read;
> +	c->no_chk_data_crc	= reconf->no_chk_data_crc;
> +	c->default_compr	= reconf->default_compr;

We cannot overwrite old configurations with non-fully initialized new 
configurations directly, otherwise some old options will disappear, for 
example:
[root at localhost ~]# mount -ocompr=lzo /dev/ubi0_0 temp
[root at localhost ~]# mount | grep ubifs
/dev/ubi0_0 on /root/temp type ubifs 
(rw,relatime,compr=lzo,assert=read-only,ubi=0,vol=0)
The compressor is set as lzo.
[root at localhost ~]# mount -oremount /dev/ubi0_0 temp
[root at localhost ~]# mount | grep ubifs
/dev/ubi0_0 on /root/temp type ubifs 
(rw,relatime,assert=read-only,ubi=0,vol=0)

The compressor is not lzo anymore.

> +	c->assert_action	= reconf->assert_action;
>   
> -	if (c->ro_mount && !(*flags & SB_RDONLY)) {
> +	if (c->ro_mount && !(fc->sb_flags & SB_RDONLY)) {
>   		if (c->ro_error) {
>   			ubifs_msg(c, "cannot re-mount R/W due to prior errors");
>   			return -EROFS;