locks: allow {vfs,posix}_lock_file to return conflicting lock

The nfsv4 protocol's lock operation, in the case of a conflict, returns
information about the conflicting lock.

It's unclear how clients can use this, so for now we're not going so far as to
add a filesystem method that can return a conflicting lock, but we may as well
return something in the local case when it's easy to.

Signed-off-by: Marc Eshel <eshel@almaden.ibm.com>
Signed-off-by: "J. Bruce Fields" <bfields@citi.umich.edu>

fs/lockd/svclock.c

@@ -363,7 +363,7 @@ again:
 	} else
 		lock = &block->b_call->a_args.lock;
 
-	error = posix_lock_file(file->f_file, &lock->fl);
+	error = posix_lock_file(file->f_file, &lock->fl, NULL);
 	lock->fl.fl_flags &= ~FL_SLEEP;
 
 	dprintk("lockd: posix_lock_file returned %d\n", error);
@@ -467,7 +467,7 @@ nlmsvc_unlock(struct nlm_file *file, struct nlm_lock *lock)
 	nlmsvc_cancel_blocked(file, lock);
 
 	lock->fl.fl_type = F_UNLCK;
-	error = posix_lock_file(file->f_file, &lock->fl);
+	error = posix_lock_file(file->f_file, &lock->fl, NULL);
 
 	return (error < 0)? nlm_lck_denied_nolocks : nlm_granted;
 }
@@ -569,7 +569,7 @@ nlmsvc_grant_blocked(struct nlm_block *block)
 
 	/* Try the lock operation again */
 	lock->fl.fl_flags |= FL_SLEEP;
-	error = posix_lock_file(file->f_file, &lock->fl);
+	error = posix_lock_file(file->f_file, &lock->fl, NULL);
 	lock->fl.fl_flags &= ~FL_SLEEP;
 
 	switch (error) {

fs/lockd/svcsubs.c

@@ -182,7 +182,7 @@ again:
 			lock.fl_type  = F_UNLCK;
 			lock.fl_start = 0;
 			lock.fl_end   = OFFSET_MAX;
-			if (posix_lock_file(file->f_file, &lock) < 0) {
+			if (posix_lock_file(file->f_file, &lock, NULL) < 0) {
 				printk("lockd: unlock failure in %s:%d\n",
 						__FILE__, __LINE__);
 				return 1;

fs/locks.c

@@ -801,7 +801,7 @@ out:
 	return error;
 }
 
-static int __posix_lock_file_conf(struct inode *inode, struct file_lock *request, struct file_lock *conflock)
+static int __posix_lock_file(struct inode *inode, struct file_lock *request, struct file_lock *conflock)
 {
 	struct file_lock *fl;
 	struct file_lock *new_fl = NULL;
@@ -1007,6 +1007,7 @@ static int __posix_lock_file_conf(struct inode *inode, struct file_lock *request
  * posix_lock_file - Apply a POSIX-style lock to a file
  * @filp: The file to apply the lock to
  * @fl: The lock to be applied
+ * @conflock: Place to return a copy of the conflicting lock, if found.
  *
  * Add a POSIX style lock to a file.
  * We merge adjacent & overlapping locks whenever possible.
@@ -1016,26 +1017,12 @@ static int __posix_lock_file_conf(struct inode *inode, struct file_lock *request
  * whether or not a lock was successfully freed by testing the return
  * value for -ENOENT.
  */
-int posix_lock_file(struct file *filp, struct file_lock *fl)
-{
-	return __posix_lock_file_conf(filp->f_path.dentry->d_inode, fl, NULL);
-}
-EXPORT_SYMBOL(posix_lock_file);
-
-/**
- * posix_lock_file_conf - Apply a POSIX-style lock to a file
- * @filp: The file to apply the lock to
- * @fl: The lock to be applied
- * @conflock: Place to return a copy of the conflicting lock, if found.
- *
- * Except for the conflock parameter, acts just like posix_lock_file.
- */
-int posix_lock_file_conf(struct file *filp, struct file_lock *fl,
+int posix_lock_file(struct file *filp, struct file_lock *fl,
 			struct file_lock *conflock)
 {
-	return __posix_lock_file_conf(filp->f_path.dentry->d_inode, fl, conflock);
+	return __posix_lock_file(filp->f_path.dentry->d_inode, fl, conflock);
 }
-EXPORT_SYMBOL(posix_lock_file_conf);
+EXPORT_SYMBOL(posix_lock_file);
 
 /**
  * posix_lock_file_wait - Apply a POSIX-style lock to a file
@@ -1051,7 +1038,7 @@ int posix_lock_file_wait(struct file *filp, struct file_lock *fl)
 	int error;
 	might_sleep ();
 	for (;;) {
-		error = posix_lock_file(filp, fl);
+		error = posix_lock_file(filp, fl, NULL);
 		if ((error != -EAGAIN) || !(fl->fl_flags & FL_SLEEP))
 			break;
 		error = wait_event_interruptible(fl->fl_wait, !fl->fl_next);
@@ -1123,7 +1110,7 @@ int locks_mandatory_area(int read_write, struct inode *inode,
 	fl.fl_end = offset + count - 1;
 
 	for (;;) {
-		error = __posix_lock_file_conf(inode, &fl, NULL);
+		error = __posix_lock_file(inode, &fl, NULL);
 		if (error != -EAGAIN)
 			break;
 		if (!(fl.fl_flags & FL_SLEEP))
@@ -1703,13 +1690,21 @@ out:
  * @filp: The file to apply the lock to
  * @cmd: type of locking operation (F_SETLK, F_GETLK, etc.)
  * @fl: The lock to be applied
+ * @conf: Place to return a copy of the conflicting lock, if found.
+ *
+ * A caller that doesn't care about the conflicting lock may pass NULL
+ * as the final argument.
+ *
+ * If the filesystem defines a private ->lock() method, then @conf will
+ * be left unchanged; so a caller that cares should initialize it to
+ * some acceptable default.
  */
-int vfs_lock_file(struct file *filp, unsigned int cmd, struct file_lock *fl)
+int vfs_lock_file(struct file *filp, unsigned int cmd, struct file_lock *fl, struct file_lock *conf)
 {
 	if (filp->f_op && filp->f_op->lock)
 		return filp->f_op->lock(filp, cmd, fl);
 	else
-		return posix_lock_file(filp, fl);
+		return posix_lock_file(filp, fl, conf);
 }
 EXPORT_SYMBOL_GPL(vfs_lock_file);
 
@@ -1776,7 +1771,7 @@ again:
 		goto out;
 
 	for (;;) {
-		error = vfs_lock_file(filp, cmd, file_lock);
+		error = vfs_lock_file(filp, cmd, file_lock, NULL);
 		if (error != -EAGAIN || cmd == F_SETLK)
 			break;
 		error = wait_event_interruptible(file_lock->fl_wait,
@@ -1902,7 +1897,7 @@ again:
 		goto out;
 
 	for (;;) {
-		error = vfs_lock_file(filp, cmd, file_lock);
+		error = vfs_lock_file(filp, cmd, file_lock, NULL);
 		if (error != -EAGAIN || cmd == F_SETLK64)
 			break;
 		error = wait_event_interruptible(file_lock->fl_wait,
@@ -1956,7 +1951,7 @@ void locks_remove_posix(struct file *filp, fl_owner_t owner)
 	lock.fl_ops = NULL;
 	lock.fl_lmops = NULL;
 
-	vfs_lock_file(filp, F_SETLK, &lock);
+	vfs_lock_file(filp, F_SETLK, &lock, NULL);
 
 	if (lock.fl_ops && lock.fl_ops->fl_release_private)
 		lock.fl_ops->fl_release_private(&lock);

fs/nfsd/nfs4state.c

@@ -2657,6 +2657,7 @@ nfsd4_lock(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
 	struct file_lock conflock;
 	__be32 status = 0;
 	unsigned int strhashval;
+	unsigned int cmd;
 	int err;
 
 	dprintk("NFSD: nfsd4_lock: start=%Ld length=%Ld\n",
@@ -2739,10 +2740,12 @@ nfsd4_lock(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
 		case NFS4_READ_LT:
 		case NFS4_READW_LT:
 			file_lock.fl_type = F_RDLCK;
+			cmd = F_SETLK;
 		break;
 		case NFS4_WRITE_LT:
 		case NFS4_WRITEW_LT:
 			file_lock.fl_type = F_WRLCK;
+			cmd = F_SETLK;
 		break;
 		default:
 			status = nfserr_inval;
@@ -2769,9 +2772,8 @@ nfsd4_lock(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
 
 	/* XXX?: Just to divert the locks_release_private at the start of
 	 * locks_copy_lock: */
-	conflock.fl_ops = NULL;
-	conflock.fl_lmops = NULL;
-	err = posix_lock_file_conf(filp, &file_lock, &conflock);
+	locks_init_lock(&conflock);
+	err = posix_lock_file(filp, &file_lock, &conflock);
 	switch (-err) {
 	case 0: /* success! */
 		update_stateid(&lock_stp->st_stateid);
@@ -2933,7 +2935,7 @@ nfsd4_locku(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
 	/*
 	*  Try to unlock the file in the VFS.
 	*/
-	err = posix_lock_file(filp, &file_lock);
+	err = posix_lock_file(filp, &file_lock, NULL);
 	if (err) {
 		dprintk("NFSD: nfs4_locku: posix_lock_file failed!\n");
 		goto out_nfserr;

include/linux/fs.h

@@ -852,12 +852,11 @@ extern void locks_copy_lock(struct file_lock *, struct file_lock *);
 extern void locks_remove_posix(struct file *, fl_owner_t);
 extern void locks_remove_flock(struct file *);
 extern int posix_test_lock(struct file *, struct file_lock *);
-extern int posix_lock_file_conf(struct file *, struct file_lock *, struct file_lock *);
-extern int posix_lock_file(struct file *, struct file_lock *);
+extern int posix_lock_file(struct file *, struct file_lock *, struct file_lock *);
 extern int posix_lock_file_wait(struct file *, struct file_lock *);
 extern int posix_unblock_lock(struct file *, struct file_lock *);
 extern int vfs_test_lock(struct file *, struct file_lock *);
-extern int vfs_lock_file(struct file *, unsigned int, struct file_lock *);
+extern int vfs_lock_file(struct file *, unsigned int, struct file_lock *, struct file_lock *);
 extern int flock_lock_file_wait(struct file *filp, struct file_lock *fl);
 extern int __break_lease(struct inode *inode, unsigned int flags);
 extern void lease_get_mtime(struct inode *, struct timespec *time);