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

[Mark Fasheh <mfasheh@suse.de>]

Hi Jeff,

On Wed, Aug 01, 2018 at 07:03:54AM -0400, Jeff Layton wrote:
> 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.

Hmm, indeed it does call under spinlock. I'll hve to rethink how to approach
this in fs/locks.c

Thanks,
	--Mark