Re: [PATCH] lockd: rip out deferred lock handling from testlock codepath

[Kinglong Mee <kinglongmee@gmail.com>]

I'd like this patch.

Reviewed-by: Kinglong Mee <kinglongmee@gmail.com>

On 8/21/2014 23:45, Jeff Layton wrote:
> As Kinglong points out, the nlm_block->b_fl field is no longer used at
> all. Also, vfs_test_lock in the generic locking code will only return
> FILE_LOCK_DEFERRED if FL_SLEEP is set, and it isn't here.
> 
> The only other place that returns that value is the DLM lock code, but
> it only does that in dlm_posix_lock, never in dlm_posix_get.
> 
> Remove all of the deferred locking code from the testlock codepath
> since it doesn't appear to ever be used anyway.
> 
> I do have a small concern that this might cause a behavior change in the
> case where you have a block already sitting on the list when the
> testlock request comes in, but that looks like it doesn't really work
> properly anyway. I think it's best to just pass that down to
> vfs_test_lock and let the filesystem report that instead of trying to
> infer what's going on with the lock by looking at an existing block.
> 
> Cc: cluster-devel@redhat.com
> Reported-by: Kinglong Mee <kinglongmee@gmail.com>
> Signed-off-by: Jeff Layton <jlayton@primarydata.com>
> ---
>  fs/lockd/svclock.c          | 55 +++++----------------------------------------
>  include/linux/lockd/lockd.h |  1 -
>  2 files changed, 6 insertions(+), 50 deletions(-)
> 
> diff --git a/fs/lockd/svclock.c b/fs/lockd/svclock.c
> index acfa94d5b489..13db95f54176 100644
> --- a/fs/lockd/svclock.c
> +++ b/fs/lockd/svclock.c
> @@ -245,7 +245,6 @@ nlmsvc_create_block(struct svc_rqst *rqstp, struct nlm_host *host,
>  	block->b_daemon = rqstp->rq_server;
>  	block->b_host   = host;
>  	block->b_file   = file;
> -	block->b_fl = NULL;
>  	file->f_count++;
>  
>  	/* Add to file's list of blocks */
> @@ -295,7 +294,6 @@ static void nlmsvc_free_block(struct kref *kref)
>  	nlmsvc_freegrantargs(block->b_call);
>  	nlmsvc_release_call(block->b_call);
>  	nlm_release_file(block->b_file);
> -	kfree(block->b_fl);
>  	kfree(block);
>  }
>  
> @@ -508,7 +506,6 @@ nlmsvc_testlock(struct svc_rqst *rqstp, struct nlm_file *file,
>  		struct nlm_host *host, struct nlm_lock *lock,
>  		struct nlm_lock *conflock, struct nlm_cookie *cookie)
>  {
> -	struct nlm_block 	*block = NULL;
>  	int			error;
>  	__be32			ret;
>  
> @@ -519,63 +516,26 @@ nlmsvc_testlock(struct svc_rqst *rqstp, struct nlm_file *file,
>  				(long long)lock->fl.fl_start,
>  				(long long)lock->fl.fl_end);
>  
> -	/* Get existing block (in case client is busy-waiting) */
> -	block = nlmsvc_lookup_block(file, lock);
> -
> -	if (block == NULL) {
> -		struct file_lock *conf = kzalloc(sizeof(*conf), GFP_KERNEL);
> -
> -		if (conf == NULL)
> -			return nlm_granted;
> -		block = nlmsvc_create_block(rqstp, host, file, lock, cookie);
> -		if (block == NULL) {
> -			kfree(conf);
> -			return nlm_granted;
> -		}
> -		block->b_fl = conf;
> -	}
> -	if (block->b_flags & B_QUEUED) {
> -		dprintk("lockd: nlmsvc_testlock deferred block %p flags %d fl %p\n",
> -			block, block->b_flags, block->b_fl);
> -		if (block->b_flags & B_TIMED_OUT) {
> -			nlmsvc_unlink_block(block);
> -			ret = nlm_lck_denied;
> -			goto out;
> -		}
> -		if (block->b_flags & B_GOT_CALLBACK) {
> -			nlmsvc_unlink_block(block);
> -			if (block->b_fl != NULL
> -					&& block->b_fl->fl_type != F_UNLCK) {
> -				lock->fl = *block->b_fl;
> -				goto conf_lock;
> -			} else {
> -				ret = nlm_granted;
> -				goto out;
> -			}
> -		}
> -		ret = nlm_drop_reply;
> -		goto out;
> -	}
> -
>  	if (locks_in_grace(SVC_NET(rqstp))) {
>  		ret = nlm_lck_denied_grace_period;
>  		goto out;
>  	}
> +
>  	error = vfs_test_lock(file->f_file, &lock->fl);
> -	if (error == FILE_LOCK_DEFERRED) {
> -		ret = nlmsvc_defer_lock_rqst(rqstp, block);
> -		goto out;
> -	}
>  	if (error) {
> +		/* We can't currently deal with deferred test requests */
> +		if (error == FILE_LOCK_DEFERRED)
> +			WARN_ON_ONCE(1);
> +
>  		ret = nlm_lck_denied_nolocks;
>  		goto out;
>  	}
> +
>  	if (lock->fl.fl_type == F_UNLCK) {
>  		ret = nlm_granted;
>  		goto out;
>  	}
>  
> -conf_lock:
>  	dprintk("lockd: conflicting lock(ty=%d, %Ld-%Ld)\n",
>  		lock->fl.fl_type, (long long)lock->fl.fl_start,
>  		(long long)lock->fl.fl_end);
> @@ -589,8 +549,6 @@ conf_lock:
>  	locks_release_private(&lock->fl);
>  	ret = nlm_lck_denied;
>  out:
> -	if (block)
> -		nlmsvc_release_block(block);
>  	return ret;
>  }
>  
> @@ -661,7 +619,6 @@ nlmsvc_cancel_blocked(struct net *net, struct nlm_file *file, struct nlm_lock *l
>   * This is a callback from the filesystem for VFS file lock requests.
>   * It will be used if lm_grant is defined and the filesystem can not
>   * respond to the request immediately.
> - * For GETLK request it will copy the reply to the nlm_block.
>   * For SETLK or SETLKW request it will get the local posix lock.
>   * In all cases it will move the block to the head of nlm_blocked q where
>   * nlmsvc_retry_blocked() can send back a reply for SETLKW or revisit the
> diff --git a/include/linux/lockd/lockd.h b/include/linux/lockd/lockd.h
> index 219d79627c05..ff82a32871b5 100644
> --- a/include/linux/lockd/lockd.h
> +++ b/include/linux/lockd/lockd.h
> @@ -178,7 +178,6 @@ struct nlm_block {
>  	unsigned char		b_granted;	/* VFS granted lock */
>  	struct nlm_file *	b_file;		/* file in question */
>  	struct cache_req *	b_cache_req;	/* deferred request handling */
> -	struct file_lock *	b_fl;		/* set for GETLK */
>  	struct cache_deferred_req * b_deferred_req;
>  	unsigned int		b_flags;	/* block flags */
>  #define B_QUEUED		1	/* lock queued */
>