Re: [PATCH v7 10/17] locks: make /proc/locks show IS_FILE_PVT locks with a P suffix

[Jeffrey Layton <jlayton@redhat.com>]

On Mon, 24 Mar 2014 20:20:47 -0400
"J. Bruce Fields" <bfields@fieldses.org> wrote:

> On Wed, Mar 19, 2014 at 04:45:54PM -0400, Jeff Layton wrote:
> > In a later patch, we'll be adding a new type of lock that's owned by
> > the struct file instead of the files_struct. Those sorts of locks
> > will be flagged with a new IS_FILE_PVT flag.
> > 
> > Add a "P" suffix to the POSIX lock output in /proc/locks for locks
> > that have FL_FILE_PVT set to distinguish them from "classic" POSIX
> > locks.
> 
> ACK, though I'm curious:
> 
> > Signed-off-by: Jeff Layton <jlayton@redhat.com>
> > ---
> >  fs/locks.c         | 9 +++++++--
> >  include/linux/fs.h | 1 +
> >  2 files changed, 8 insertions(+), 2 deletions(-)
> > 
> > diff --git a/fs/locks.c b/fs/locks.c
> > index 4d4e790150e0..f1b9b149dd39 100644
> > --- a/fs/locks.c
> > +++ b/fs/locks.c
> > @@ -135,6 +135,7 @@
> >  #define IS_POSIX(fl)	(fl->fl_flags & FL_POSIX)
> >  #define IS_FLOCK(fl)	(fl->fl_flags & FL_FLOCK)
> >  #define IS_LEASE(fl)	(fl->fl_flags & (FL_LEASE|FL_DELEG))
> > +#define IS_FILE_PVT(fl)	(fl->fl_flags & FL_FILE_PVT)
> >  
> >  static bool lease_breaking(struct file_lock *fl)
> >  {
> > @@ -2313,8 +2314,12 @@ static void lock_get_status(struct seq_file
> > *f, struct file_lock *fl, 
> >  	seq_printf(f, "%lld:%s ", id, pfx);
> >  	if (IS_POSIX(fl)) {
> > -		seq_printf(f, "%6s %s ",
> > -			     (fl->fl_flags & FL_ACCESS) ?
> > "ACCESS" : "POSIX ",
> > +		if (fl->fl_flags & FL_ACCESS)
> > +			seq_printf(f, "ACCESS");
> 
> Are FL_ACCESS locks ever put on any global list?  Wouldn't it be a bug
> to run across one here?
> 
> --b.
> 

Yes, that can happen (and yes, that surprised me too)

locks_mandatory_area can send down FL_ACCESS|FL_POSIX|FL_SLEEP

...which makes sense given the use-case there but I do wonder if there
might be a better way...
 
> > +		else
> > +			seq_printf(f, "POSIX%c", IS_FILE_PVT(fl) ?
> > 'P' : ' '); +
> > +		seq_printf(f, " %s ",
> >  			     (inode == NULL) ? "*NOINODE*" :
> >  			     mandatory_lock(inode) ? "MANDATORY" :
> > "ADVISORY "); } else if (IS_FLOCK(fl)) {
> > diff --git a/include/linux/fs.h b/include/linux/fs.h
> > index 7527d96913d3..5ddeb8de5e77 100644
> > --- a/include/linux/fs.h
> > +++ b/include/linux/fs.h
> > @@ -888,6 +888,7 @@ static inline int file_check_writeable(struct
> > file *filp) #define FL_SLEEP	128	/* A blocking lock */
> >  #define FL_DOWNGRADE_PENDING	256 /* Lease is being
> > downgraded */ #define FL_UNLOCK_PENDING	512 /* Lease is
> > being broken */ +#define FL_FILE_PVT	1024	/* lock is
> > private to the file */ 
> >  /*
> >   * Special return value from posix_lock_file() and vfs_lock_file()
> > for -- 
> > 1.8.5.3
> > 



-- 
Jeff Layton <jlayton@redhat.com>