linux-kernel - RE: [RFC PATCH v2 5/5] locks: report l_pid as -1 for FL_FILP

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Message-ID: <0d1101cee619$ad866500$08932f00$@mindspring.com>
Date:	Wed, 20 Nov 2013 09:55:18 -0800
From:	"Frank Filz" <ffilzlnx@...dspring.com>
To:	"'Jeff Layton'" <jlayton@...hat.com>,
	<linux-fsdevel@...r.kernel.org>
Cc:	<linux-kernel@...r.kernel.org>,
	<nfs-ganesha-devel@...ts.sourceforge.net>,
	<samba-technical@...ts.samba.org>
Subject: RE: [RFC PATCH v2 5/5] locks: report l_pid as -1 for FL_FILP_PRIVATE locks

> FL_FILP_PRIVATE locks are no longer tied to a particular PID, and are
instead
> inheritable by child processes. Report a l_pid of '-1' for these sorts of
locks
> since the pid is somewhat meaningless for them.

Hmm, I suppose in the case of a process that acquires a private lock, forks
(passing the lock to the child process) and then exits, pid would be
meaningless, but I wonder how common that case is compared to a
multi-threaded process (especially a file server) that will hold many
private locks, and not pass them to child processes (and exit)?

I.e. as a future user of this feature, I wonder if I'm going to want to know
that THESE private locks are owned by Ganesha and THOSE are owned by Samba?

Frank

> Signed-off-by: Jeff Layton <jlayton@...hat.com>
> ---
>  fs/locks.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/locks.c b/fs/locks.c
> index d5fb853..8a4d4e4 100644
> --- a/fs/locks.c
> +++ b/fs/locks.c
> @@ -1889,7 +1889,7 @@ EXPORT_SYMBOL_GPL(vfs_test_lock);
> 
>  static int posix_lock_to_flock(struct flock *flock, struct file_lock *fl)
{
> -	flock->l_pid = fl->fl_pid;
> +	flock->l_pid = IS_FILP_PVT(fl) ? -1 : fl->fl_pid;
>  #if BITS_PER_LONG == 32
>  	/*
>  	 * Make sure we can represent the posix lock via @@ -1911,7 +1911,7
> @@ static int posix_lock_to_flock(struct flock *flock, struct file_lock
*fl)  #if
> BITS_PER_LONG == 32  static void posix_lock_to_flock64(struct flock64
> *flock, struct file_lock *fl)  {
> -	flock->l_pid = fl->fl_pid;
> +	flock->l_pid = IS_FILP_PVT(fl) ? -1 : fl->fl_pid;
>  	flock->l_start = fl->fl_start;
>  	flock->l_len = fl->fl_end == OFFSET_MAX ? 0 :
>  		fl->fl_end - fl->fl_start + 1;
> --
> 1.8.3.1
> 
> --
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