Re: [PATCH v3] btrfs_get_tree_subvol(): switch from fc_mount() to vfs_create_mount()

[Qu Wenruo <wqu@suse.com>]

在 2025/5/7 05:28, Al Viro 写道:
> [Aaarghh...]
> it's simpler to do btrfs_reconfigure_for_mount() right after vfs_get_tree() -
> no need to mess with ->s_umount.
>      
> [fix for braino(s) folded in - kudos to Klara Modin <klarasmodin@gmail.com>]
> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

Reviewed-by: Qu Wenruo <wqu@suse.com>
Test-by: Qu Wenruo <wqu@suse.com>

Although the commit message can be enhanced a little, I can handle it at 
merge time, no need to re-send.

Thanks,
Qu

> ---
> diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
> index 7121d8c7a318..592ed044340c 100644
> --- a/fs/btrfs/super.c
> +++ b/fs/btrfs/super.c
> @@ -1984,17 +1984,13 @@ static int btrfs_get_tree_super(struct fs_context *fc)
>    * btrfs or not, setting the whole super block RO.  To make per-subvolume mounting
>    * work with different options work we need to keep backward compatibility.
>    */
> -static int btrfs_reconfigure_for_mount(struct fs_context *fc, struct vfsmount *mnt)
> +static int btrfs_reconfigure_for_mount(struct fs_context *fc)
>   {
>   	int ret = 0;
>   
> -	if (fc->sb_flags & SB_RDONLY)
> -		return ret;
> -
> -	down_write(&mnt->mnt_sb->s_umount);
> -	if (!(fc->sb_flags & SB_RDONLY) && (mnt->mnt_sb->s_flags & SB_RDONLY))
> +	if (!(fc->sb_flags & SB_RDONLY) && (fc->root->d_sb->s_flags & SB_RDONLY))
>   		ret = btrfs_reconfigure(fc);
> -	up_write(&mnt->mnt_sb->s_umount);
> +
>   	return ret;
>   }
>   
> @@ -2047,17 +2043,18 @@ static int btrfs_get_tree_subvol(struct fs_context *fc)
>   	security_free_mnt_opts(&fc->security);
>   	fc->security = NULL;
>   
> -	mnt = fc_mount(dup_fc);
> -	if (IS_ERR(mnt)) {
> -		put_fs_context(dup_fc);
> -		return PTR_ERR(mnt);
> +	ret = vfs_get_tree(dup_fc);
> +	if (!ret) {
> +		ret = btrfs_reconfigure_for_mount(dup_fc);
> +		up_write(&dup_fc->root->d_sb->s_umount);
>   	}
> -	ret = btrfs_reconfigure_for_mount(dup_fc, mnt);
> +	if (!ret)
> +		mnt = vfs_create_mount(dup_fc);
> +	else
> +		mnt = ERR_PTR(ret);
>   	put_fs_context(dup_fc);
> -	if (ret) {
> -		mntput(mnt);
> -		return ret;
> -	}
> +	if (IS_ERR(mnt))
> +		return PTR_ERR(mnt);
>   
>   	/*
>   	 * This free's ->subvol_name, because if it isn't set we have to
>