Merge tag 'filelock-v5.4-1' of git://git.kernel.org/pub/scm/linux/kernel/git/jlayton/linux

Pull file locking updates from Jeff Layton:
 "Just a couple of minor bugfixes, a revision to a tracepoint to account
  for some earlier changes to the internals, and a patch to add a
  pr_warn message when someone tries to mount a filesystem with '-o
  mand' on a kernel that has that support disabled"

* tag 'filelock-v5.4-1' of git://git.kernel.org/pub/scm/linux/kernel/git/jlayton/linux:
  locks: fix a memory leak bug in __break_lease()
  locks: print a warning when mount fails due to lack of "mand" support
  locks: Fix procfs output for file leases
  locks: revise generic_add_lease tracepoint

Documentation/filesystems/mandatory-locking.txt

@@ -169,3 +169,13 @@ havoc if they lock crucial files. The way around it is to change the file
 permissions (remove the setgid bit) before trying to read or write to it.
 Of course, that might be a bit tricky if the system is hung :-(
 
+7. The "mand" mount option
+--------------------------
+Mandatory locking is disabled on all filesystems by default, and must be
+administratively enabled by mounting with "-o mand". That mount option
+is only allowed if the mounting task has the CAP_SYS_ADMIN capability.
+
+Since kernel v4.5, it is possible to disable mandatory locking
+altogether by setting CONFIG_MANDATORY_FILE_LOCKING to "n". A kernel
+with this disabled will reject attempts to mount filesystems with the
+"mand" mount option with the error status EPERM.

fs/locks.c

@@ -1592,7 +1592,7 @@ int __break_lease(struct inode *inode, unsigned int mode, unsigned int type)
 	ctx = smp_load_acquire(&inode->i_flctx);
 	if (!ctx) {
 		WARN_ON_ONCE(1);
-		return error;
+		goto free_lock;
 	}
 
 	percpu_down_read(&file_rwsem);
@@ -1672,6 +1672,7 @@ out:
 	spin_unlock(&ctx->flc_lock);
 	percpu_up_read(&file_rwsem);
 	locks_dispose_list(&dispose);
+free_lock:
 	locks_free_lock(new_fl);
 	return error;
 }
@@ -2784,10 +2785,10 @@ static void lock_get_status(struct seq_file *f, struct file_lock *fl,
 			       ? (fl->fl_type & LOCK_WRITE) ? "RW   " : "READ "
 			       : (fl->fl_type & LOCK_WRITE) ? "WRITE" : "NONE ");
 	} else {
-		seq_printf(f, "%s ",
+		int type = IS_LEASE(fl) ? target_leasetype(fl) : fl->fl_type;
-			       (lease_breaking(fl))
+
-			       ? (fl->fl_type == F_UNLCK) ? "UNLCK" : "READ "
+		seq_printf(f, "%s ", (type == F_WRLCK) ? "WRITE" :
-			       : (fl->fl_type == F_WRLCK) ? "WRITE" : "READ ");
+				     (type == F_RDLCK) ? "READ" : "UNLCK");
 	}
 	if (inode) {
 		/* userspace relies on this representation of dev_t */

fs/namespace.c

@@ -1643,13 +1643,18 @@ static inline bool may_mount(void)
 	return ns_capable(current->nsproxy->mnt_ns->user_ns, CAP_SYS_ADMIN);
 }
 
+#ifdef	CONFIG_MANDATORY_FILE_LOCKING
 static inline bool may_mandlock(void)
 {
-#ifndef	CONFIG_MANDATORY_FILE_LOCKING
-	return false;
-#endif
 	return capable(CAP_SYS_ADMIN);
 }
+#else
+static inline bool may_mandlock(void)
+{
+	pr_warn("VFS: \"mand\" mount option not supported");
+	return false;
+}
+#endif
 
 /*
  * Now umount can handle mount points as well as block devices.

include/trace/events/filelock.h

@@ -176,7 +176,7 @@ TRACE_EVENT(generic_add_lease,
 	TP_STRUCT__entry(
 		__field(unsigned long, i_ino)
 		__field(int, wcount)
-		__field(int, dcount)
+		__field(int, rcount)
 		__field(int, icount)
 		__field(dev_t, s_dev)
 		__field(fl_owner_t, fl_owner)
@@ -188,16 +188,16 @@ TRACE_EVENT(generic_add_lease,
 		__entry->s_dev = inode->i_sb->s_dev;
 		__entry->i_ino = inode->i_ino;
 		__entry->wcount = atomic_read(&inode->i_writecount);
-		__entry->dcount = d_count(fl->fl_file->f_path.dentry);
+		__entry->rcount = atomic_read(&inode->i_readcount);
 		__entry->icount = atomic_read(&inode->i_count);
-		__entry->fl_owner = fl ? fl->fl_owner : NULL;
+		__entry->fl_owner = fl->fl_owner;
-		__entry->fl_flags = fl ? fl->fl_flags : 0;
+		__entry->fl_flags = fl->fl_flags;
-		__entry->fl_type = fl ? fl->fl_type : 0;
+		__entry->fl_type = fl->fl_type;
 	),
 
-	TP_printk("dev=0x%x:0x%x ino=0x%lx wcount=%d dcount=%d icount=%d fl_owner=0x%p fl_flags=%s fl_type=%s",
+	TP_printk("dev=0x%x:0x%x ino=0x%lx wcount=%d rcount=%d icount=%d fl_owner=0x%p fl_flags=%s fl_type=%s",
 		MAJOR(__entry->s_dev), MINOR(__entry->s_dev),
-		__entry->i_ino, __entry->wcount, __entry->dcount,
+		__entry->i_ino, __entry->wcount, __entry->rcount,
 		__entry->icount, __entry->fl_owner,
 		show_fl_flags(__entry->fl_flags),
 		show_fl_type(__entry->fl_type))