4 files changed, 34 insertions, 7 deletions

diff --git a/Documentation/filesystems/Locking b/Documentation/filesystems/Locking
index c2963a74fbc3..2db7c9e492e9 100644
--- a/Documentation/filesystems/Locking
+++ b/Documentation/filesystems/Locking
@@ -349,6 +349,7 @@ fl_release_private:	maybe		no
 ----------------------- lock_manager_operations ---------------------------
 prototypes:
         int (*lm_compare_owner)(struct file_lock *, struct file_lock *);
+        unsigned long (*lm_owner_key)(struct file_lock *);
         void (*lm_notify)(struct file_lock *);  /* unblock callback */
         int (*lm_grant)(struct file_lock *, struct file_lock *, int);
         void (*lm_break)(struct file_lock *); /* break_lease callback */
@@ -358,16 +359,21 @@ locking rules:
 
                         inode->i_lock   file_lock_lock  may block
 lm_compare_owner:       yes[1]          maybe           no
+lm_owner_key            yes[1]          yes             no
 lm_notify:              yes             yes             no
 lm_grant:               no              no              no
 lm_break:               yes             no              no
 lm_change               yes             no              no
 
-[1]:    ->lm_compare_owner is generally called with *an* inode->i_lock held. It
-may not be the i_lock of the inode for either file_lock being compared! This is
-the case with deadlock detection, since the code has to chase down the owners
-of locks that may be entirely unrelated to the one on which the lock is being
-acquired. When doing a search for deadlocks, the file_lock_lock is also held.
+[1]:    ->lm_compare_owner and ->lm_owner_key are generally called with
+*an* inode->i_lock held. It may not be the i_lock of the inode
+associated with either file_lock argument! This is the case with deadlock
+detection, since the code has to chase down the owners of locks that may
+be entirely unrelated to the one on which the lock is being acquired.
+For deadlock detection however, the file_lock_lock is also held. The
+fact that these locks are held ensures that the file_locks do not
+disappear out from under you while doing the comparison or generating an
+owner key.
 
 --------------------------- buffer_head -----------------------------------
 prototypes:
diff --git a/fs/lockd/svclock.c b/fs/lockd/svclock.c
index a469098682c4..067778b0ccc9 100644
--- a/fs/lockd/svclock.c
+++ b/fs/lockd/svclock.c
@@ -744,8 +744,20 @@ static int nlmsvc_same_owner(struct file_lock *fl1, struct file_lock *fl2)
         return fl1->fl_owner == fl2->fl_owner && fl1->fl_pid == fl2->fl_pid;
 }
 
+/*
+ * Since NLM uses two "keys" for tracking locks, we need to hash them down
+ * to one for the blocked_hash. Here, we're just xor'ing the host address
+ * with the pid in order to create a key value for picking a hash bucket.
+ */
+static unsigned long
+nlmsvc_owner_key(struct file_lock *fl)
+{
+        return (unsigned long)fl->fl_owner ^ (unsigned long)fl->fl_pid;
+}
+
 const struct lock_manager_operations nlmsvc_lock_operations = {
         .lm_compare_owner = nlmsvc_same_owner,
+        .lm_owner_key = nlmsvc_owner_key,
         .lm_notify = nlmsvc_notify_blocked,
         .lm_grant = nlmsvc_grant_deferred,
 };
diff --git a/fs/locks.c b/fs/locks.c
index 71d847cbbb63..6242e0b1c69c 100644
--- a/fs/locks.c
+++ b/fs/locks.c
@@ -521,10 +521,18 @@ locks_delete_global_locks(struct file_lock *fl)
         spin_unlock(&file_lock_lock);
 }
 
+static unsigned long
+posix_owner_key(struct file_lock *fl)
+{
+        if (fl->fl_lmops && fl->fl_lmops->lm_owner_key)
+                return fl->fl_lmops->lm_owner_key(fl);
+        return (unsigned long)fl->fl_owner;
+}
+
 static inline void
 locks_insert_global_blocked(struct file_lock *waiter)
 {
-        hash_add(blocked_hash, &waiter->fl_link, (unsigned long)waiter->fl_owner);
+        hash_add(blocked_hash, &waiter->fl_link, posix_owner_key(waiter));
 }
 
 static inline void
@@ -757,7 +765,7 @@ static struct file_lock *what_owner_is_waiting_for(struct file_lock *block_fl)
 {
         struct file_lock *fl;
 
-        hash_for_each_possible(blocked_hash, fl, fl_link, (unsigned long)block_fl->fl_owner) {
+        hash_for_each_possible(blocked_hash, fl, fl_link, posix_owner_key(block_fl)) {
                 if (posix_same_owner(fl, block_fl))
                         return fl->fl_next;
         }
diff --git a/include/linux/fs.h b/include/linux/fs.h
index fab064a3b65f..a137a73fc1fe 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -908,6 +908,7 @@ struct file_lock_operations {
 
 struct lock_manager_operations {
         int (*lm_compare_owner)(struct file_lock *, struct file_lock *);
+        unsigned long (*lm_owner_key)(struct file_lock *);
         void (*lm_notify)(struct file_lock *);  /* unblock callback */
         int (*lm_grant)(struct file_lock *, struct file_lock *, int);
         void (*lm_break)(struct file_lock *);