Re: [PATCH 4/4] locks: map correct ino/dev pairs when exporting to userspace

[Jeff Layton <jlayton@poochiereds.net>]

On Tue, 2018-07-31 at 14:10 -0700, Mark Fasheh wrote:
> /proc/locks does not always print the correct inode number/device pair.
> Update lock_get_status() to use vfs_map_unique_ino_dev() to get the real,
> unique values for userspace.
> 
> Signed-off-by: Mark Fasheh <mfasheh@suse.de>
> ---
>  fs/locks.c | 12 +++++++++---
>  1 file changed, 9 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/locks.c b/fs/locks.c
> index db7b6917d9c5..3a012df87fd8 100644
> --- a/fs/locks.c
> +++ b/fs/locks.c
> @@ -2621,6 +2621,7 @@ static void lock_get_status(struct seq_file *f, struct file_lock *fl,
>  			    loff_t id, char *pfx)
>  {
>  	struct inode *inode = NULL;
> +	struct dentry *dentry;
>  	unsigned int fl_pid;
>  	struct pid_namespace *proc_pidns = file_inode(f->file)->i_sb->s_fs_info;
>  
> @@ -2633,8 +2634,10 @@ static void lock_get_status(struct seq_file *f, struct file_lock *fl,
>  	if (fl_pid == 0)
>  		return;
>  
> -	if (fl->fl_file != NULL)
> +	if (fl->fl_file != NULL) {
>  		inode = locks_inode(fl->fl_file);
> +		dentry = file_dentry(fl->fl_file);
> +	}
>  
>  	seq_printf(f, "%lld:%s ", id, pfx);
>  	if (IS_POSIX(fl)) {
> @@ -2681,10 +2684,13 @@ static void lock_get_status(struct seq_file *f, struct file_lock *fl,
>  			       : (fl->fl_type == F_WRLCK) ? "WRITE" : "READ ");
>  	}
>  	if (inode) {
> +		__u64 ino;
> +		dev_t dev;
> +
> +		vfs_map_unique_ino_dev(dentry, &ino, &dev);

This code is under a spinlock (blocked_locks_lock or ctx->flc_lock). I
don't think it'll be ok to call ->getattr while holding a spinlock.

>  		/* userspace relies on this representation of dev_t */
>  		seq_printf(f, "%d %02x:%02x:%ld ", fl_pid,
> -				MAJOR(inode->i_sb->s_dev),
> -				MINOR(inode->i_sb->s_dev), inode->i_ino);
> +				MAJOR(dev), MINOR(dev), inode->i_ino);
>  	} else {
>  		seq_printf(f, "%d <none>:0 ", fl_pid);
>  	}

-- 
Jeff Layton <jlayton@poochiereds.net>