Re: [PATCH] cifs: stuff the fl_owner into "pid" field in the lock request

[Sachin Prabhu <sprabhu-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>]

On Tue, 2016-05-24 at 06:27 -0400, Jeff Layton wrote:
> Right now, we send the tgid cross the wire. What we really want to
> send
> though is a hashed fl_owner_t since samba treats this field as a
> generic
> lockowner.
> 
> It turns out that because we enforce and release locks locally before
> they are ever sent to the server, this patch makes no difference in
> behavior. Still, setting OFD locks on the server using the process
> pid seems wrong, so I think this patch still makes sense.
> 
> Signed-off-by: Jeff Layton <jeff.layton-7I+n7zu2hftEKMMhf/gKZA@public.gmane.org>

Acked-by: Sachin Prabhu <sprabhu-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>

> ---
>  fs/cifs/cifsfs.c   |  3 +++
>  fs/cifs/cifsglob.h |  1 +
>  fs/cifs/file.c     | 14 +++++++++++---
>  3 files changed, 15 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/cifs/cifsfs.c b/fs/cifs/cifsfs.c
> index 08fa36e5b2bc..1ef5b8aee878 100644
> --- a/fs/cifs/cifsfs.c
> +++ b/fs/cifs/cifsfs.c
> @@ -87,6 +87,7 @@ extern mempool_t *cifs_req_poolp;
>  extern mempool_t *cifs_mid_poolp;
>  
>  struct workqueue_struct	*cifsiod_wq;
> +__u32 cifs_lock_secret;
>  
>  /*
>   * Bumps refcount for cifs super block.
> @@ -1271,6 +1272,8 @@ init_cifs(void)
>  	spin_lock_init(&cifs_file_list_lock);
>  	spin_lock_init(&GlobalMid_Lock);
>  
> +	get_random_bytes(&cifs_lock_secret,
> sizeof(cifs_lock_secret));
> +
>  	if (cifs_max_pending < 2) {
>  		cifs_max_pending = 2;
>  		cifs_dbg(FYI, "cifs_max_pending set to min of 2\n");
> diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h
> index bba106cdc43c..8f1d8c1e72be 100644
> --- a/fs/cifs/cifsglob.h
> +++ b/fs/cifs/cifsglob.h
> @@ -1619,6 +1619,7 @@ void cifs_oplock_break(struct work_struct
> *work);
>  
>  extern const struct slow_work_ops cifs_oplock_break_ops;
>  extern struct workqueue_struct *cifsiod_wq;
> +extern __u32 cifs_lock_secret;
>  
>  extern mempool_t *cifs_mid_poolp;
>  
> diff --git a/fs/cifs/file.c b/fs/cifs/file.c
> index 9793ae0bcaa2..d4890b6dc22d 100644
> --- a/fs/cifs/file.c
> +++ b/fs/cifs/file.c
> @@ -1112,6 +1112,12 @@ cifs_push_mandatory_locks(struct cifsFileInfo
> *cfile)
>  	return rc;
>  }
>  
> +static __u32
> +hash_lockowner(fl_owner_t owner)
> +{
> +	return cifs_lock_secret ^ hash32_ptr((const void *)owner);
> +}
> +
>  struct lock_to_push {
>  	struct list_head llist;
>  	__u64 offset;
> @@ -1178,7 +1184,7 @@ cifs_push_posix_locks(struct cifsFileInfo
> *cfile)
>  		else
>  			type = CIFS_WRLCK;
>  		lck = list_entry(el, struct lock_to_push, llist);
> -		lck->pid = flock->fl_pid;
> +		lck->pid = hash_lockowner(flock->fl_owner);
>  		lck->netfid = cfile->fid.netfid;
>  		lck->length = length;
>  		lck->type = type;
> @@ -1305,7 +1311,8 @@ cifs_getlk(struct file *file, struct file_lock
> *flock, __u32 type,
>  			posix_lock_type = CIFS_RDLCK;
>  		else
>  			posix_lock_type = CIFS_WRLCK;
> -		rc = CIFSSMBPosixLock(xid, tcon, netfid, current-
> >tgid,
> +		rc = CIFSSMBPosixLock(xid, tcon, netfid,
> +				      hash_lockowner(flock-
> >fl_owner),
>  				      flock->fl_start, length,
> flock,
>  				      posix_lock_type, wait_flag);
>  		return rc;
> @@ -1505,7 +1512,8 @@ cifs_setlk(struct file *file, struct file_lock
> *flock, __u32 type,
>  			posix_lock_type = CIFS_UNLCK;
>  
>  		rc = CIFSSMBPosixLock(xid, tcon, cfile->fid.netfid,
> -				      current->tgid, flock-
> >fl_start, length,
> +				      hash_lockowner(flock-
> >fl_owner),
> +				      flock->fl_start, length,
>  				      NULL, posix_lock_type,
> wait_flag);
>  		goto out;
>  	}