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

Qu Wenruo
2025-05-08T09:29:10Z

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
>