diff mbox

[RFC] xfs: remove i_iolock and use i_rwsem in the VFS inode instead

Message ID 20160811215444.GY30192@twins.programming.kicks-ass.net (mailing list archive)
State Superseded, archived
Headers show

Commit Message

Peter Zijlstra Aug. 11, 2016, 9:54 p.m. UTC 
On Thu, Aug 11, 2016 at 10:10:23AM -0700, Christoph Hellwig wrote:

> There is one major issue with this change though:  lockdep currently
> doesn't have a facility to assert a rw_sempahore is held exclusively,
> which means we lose the nice ability to assert locking context in
> XFS.
> 
> Peter, I think you mentioned this would be fairly easy to add to
> lockdep and the rw_semaphore code.  Any chance to come up with a proof
> of concept?

Sure, find below. Not been near a compiler.

---
 include/linux/lockdep.h  | 17 +++++++++++++++--
 kernel/locking/lockdep.c | 41 +++++++++++++++++++++++++----------------
 2 files changed, 40 insertions(+), 18 deletions(-)
diff mbox

Patch

diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h
index eabe0138eb06..7f0098d3a7d7 100644
--- a/include/linux/lockdep.h
+++ b/include/linux/lockdep.h
@@ -338,9 +338,14 @@  extern void lock_acquire(struct lockdep_map *lock, unsigned int subclass,
 extern void lock_release(struct lockdep_map *lock, int nested,
 			 unsigned long ip);
 
-#define lockdep_is_held(lock)	lock_is_held(&(lock)->dep_map)
+extern int _lock_is_held(struct lockdep_map *lock, int read);
 
-extern int lock_is_held(struct lockdep_map *lock);
+static inline int lock_is_held(struct lockdep_map *lock)
+{
+	return _lock_is_held(lock, -1);
+}
+
+#define lockdep_is_held(lock)	lock_is_held(&(lock)->dep_map)
 
 extern void lock_set_class(struct lockdep_map *lock, const char *name,
 			   struct lock_class_key *key, unsigned int subclass,
@@ -372,6 +377,14 @@  extern void lock_unpin_lock(struct lockdep_map *lock, struct pin_cookie);
 		WARN_ON(debug_locks && !lockdep_is_held(l));	\
 	} while (0)
 
+#define lockdep_assert_held_exclusive(l)	do {		\
+		WARN_ON(debug_locks && !_lockdep_is_held(l, 0));\
+	} while (0)
+
+#define lockdep_assert_held_read(l)	do {			\
+		WARN_ON(debug_locks && !_lockdep_is_held(l, 1));\
+	} while (0)
+
 #define lockdep_assert_held_once(l)	do {				\
 		WARN_ON_ONCE(debug_locks && !lockdep_is_held(l));	\
 	} while (0)
diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 589d763a49b3..abec578378e7 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -3188,7 +3188,7 @@  print_lock_nested_lock_not_held(struct task_struct *curr,
 	return 0;
 }
 
-static int __lock_is_held(struct lockdep_map *lock);
+static int __lock_is_held(struct lockdep_map *lock, int read);
 
 /*
  * This gets called for every mutex_lock*()/spin_lock*() operation.
@@ -3329,7 +3329,7 @@  static int __lock_acquire(struct lockdep_map *lock, unsigned int subclass,
 	}
 	chain_key = iterate_chain_key(chain_key, class_idx);
 
-	if (nest_lock && !__lock_is_held(nest_lock))
+	if (nest_lock && !__lock_is_held(nest_lock, -1))
 		return print_lock_nested_lock_not_held(curr, hlock, ip);
 
 	if (!validate_chain(curr, lock, hlock, chain_head, chain_key))
@@ -3390,10 +3390,17 @@  print_unlock_imbalance_bug(struct task_struct *curr, struct lockdep_map *lock,
 	return 0;
 }
 
-static int match_held_lock(struct held_lock *hlock, struct lockdep_map *lock)
+static int match_held_lock(struct held_lock *hlock, struct lockdep_map *lock, int read)
 {
-	if (hlock->instance == lock)
-		return 1;
+	if (hlock->instance == lock) {
+		if (read == -1)
+			return 1;
+
+		if (hlock->read == read)
+			return 1;
+
+		return 0;
+	}
 
 	if (hlock->references) {
 		struct lock_class *class = lock->class_cache[0];
@@ -3420,6 +3427,8 @@  static int match_held_lock(struct held_lock *hlock, struct lockdep_map *lock)
 
 		if (hlock->class_idx == class - lock_classes + 1)
 			return 1;
+
+		/* XXX do we want @read stuff for nested locks !? */
 	}
 
 	return 0;
@@ -3452,7 +3461,7 @@  __lock_set_class(struct lockdep_map *lock, const char *name,
 		 */
 		if (prev_hlock && prev_hlock->irq_context != hlock->irq_context)
 			break;
-		if (match_held_lock(hlock, lock))
+		if (match_held_lock(hlock, lock, -1))
 			goto found_it;
 		prev_hlock = hlock;
 	}
@@ -3523,7 +3532,7 @@  __lock_release(struct lockdep_map *lock, int nested, unsigned long ip)
 		 */
 		if (prev_hlock && prev_hlock->irq_context != hlock->irq_context)
 			break;
-		if (match_held_lock(hlock, lock))
+		if (match_held_lock(hlock, lock, -1))
 			goto found_it;
 		prev_hlock = hlock;
 	}
@@ -3576,7 +3585,7 @@  __lock_release(struct lockdep_map *lock, int nested, unsigned long ip)
 	return 1;
 }
 
-static int __lock_is_held(struct lockdep_map *lock)
+static int __lock_is_held(struct lockdep_map *lock, int read)
 {
 	struct task_struct *curr = current;
 	int i;
@@ -3584,7 +3593,7 @@  static int __lock_is_held(struct lockdep_map *lock)
 	for (i = 0; i < curr->lockdep_depth; i++) {
 		struct held_lock *hlock = curr->held_locks + i;
 
-		if (match_held_lock(hlock, lock))
+		if (match_held_lock(hlock, lock, read))
 			return 1;
 	}
 
@@ -3603,7 +3612,7 @@  static struct pin_cookie __lock_pin_lock(struct lockdep_map *lock)
 	for (i = 0; i < curr->lockdep_depth; i++) {
 		struct held_lock *hlock = curr->held_locks + i;
 
-		if (match_held_lock(hlock, lock)) {
+		if (match_held_lock(hlock, lock, -1)) {
 			/*
 			 * Grab 16bits of randomness; this is sufficient to not
 			 * be guessable and still allows some pin nesting in
@@ -3630,7 +3639,7 @@  static void __lock_repin_lock(struct lockdep_map *lock, struct pin_cookie cookie
 	for (i = 0; i < curr->lockdep_depth; i++) {
 		struct held_lock *hlock = curr->held_locks + i;
 
-		if (match_held_lock(hlock, lock)) {
+		if (match_held_lock(hlock, lock, -1)) {
 			hlock->pin_count += cookie.val;
 			return;
 		}
@@ -3650,7 +3659,7 @@  static void __lock_unpin_lock(struct lockdep_map *lock, struct pin_cookie cookie
 	for (i = 0; i < curr->lockdep_depth; i++) {
 		struct held_lock *hlock = curr->held_locks + i;
 
-		if (match_held_lock(hlock, lock)) {
+		if (match_held_lock(hlock, lock, -1)) {
 			if (WARN(!hlock->pin_count, "unpinning an unpinned lock\n"))
 				return;
 
@@ -3769,7 +3778,7 @@  void lock_release(struct lockdep_map *lock, int nested,
 }
 EXPORT_SYMBOL_GPL(lock_release);
 
-int lock_is_held(struct lockdep_map *lock)
+int lock_is_held(struct lockdep_map *lock, int read)
 {
 	unsigned long flags;
 	int ret = 0;
@@ -3781,7 +3790,7 @@  int lock_is_held(struct lockdep_map *lock)
 	check_flags(flags);
 
 	current->lockdep_recursion = 1;
-	ret = __lock_is_held(lock);
+	ret = __lock_is_held(lock, read);
 	current->lockdep_recursion = 0;
 	raw_local_irq_restore(flags);
 
@@ -3908,7 +3917,7 @@  __lock_contended(struct lockdep_map *lock, unsigned long ip)
 		 */
 		if (prev_hlock && prev_hlock->irq_context != hlock->irq_context)
 			break;
-		if (match_held_lock(hlock, lock))
+		if (match_held_lock(hlock, lock, -1))
 			goto found_it;
 		prev_hlock = hlock;
 	}
@@ -3961,7 +3970,7 @@  __lock_acquired(struct lockdep_map *lock, unsigned long ip)
 		 */
 		if (prev_hlock && prev_hlock->irq_context != hlock->irq_context)
 			break;
-		if (match_held_lock(hlock, lock))
+		if (match_held_lock(hlock, lock, -1))
 			goto found_it;
 		prev_hlock = hlock;
 	}