fscache: Add tracepoints

Add some tracepoints to fscache:

 (*) fscache_cookie - Tracks a cookie's usage count.

 (*) fscache_netfs - Logs registration of a network filesystem, including
     the pointer to the cookie allocated.

 (*) fscache_acquire - Logs cookie acquisition.

 (*) fscache_relinquish - Logs cookie relinquishment.

 (*) fscache_enable - Logs enablement of a cookie.

 (*) fscache_disable - Logs disablement of a cookie.

 (*) fscache_osm - Tracks execution of states in the object state machine.

and cachefiles:

 (*) cachefiles_ref - Tracks a cachefiles object's usage count.

 (*) cachefiles_lookup - Logs result of lookup_one_len().

 (*) cachefiles_mkdir - Logs result of vfs_mkdir().

 (*) cachefiles_create - Logs result of vfs_create().

 (*) cachefiles_unlink - Logs calls to vfs_unlink().

 (*) cachefiles_rename - Logs calls to vfs_rename().

 (*) cachefiles_mark_active - Logs an object becoming active.

 (*) cachefiles_wait_active - Logs a wait for an old object to be
     destroyed.

 (*) cachefiles_mark_inactive - Logs an object becoming inactive.

 (*) cachefiles_mark_buried - Logs the burial of an object.

Signed-off-by: David Howells <[email protected]>

Author: dhowells

fs/cachefiles/interface.c

@@ -177,18 +177,22 @@ static void cachefiles_lookup_complete(struct fscache_object *_object)
  * increment the usage count on an inode object (may fail if unmounting)
  */
 static
-struct fscache_object *cachefiles_grab_object(struct fscache_object *_object)
+struct fscache_object *cachefiles_grab_object(struct fscache_object *_object,
+					      enum fscache_obj_ref_trace why)
 {
 	struct cachefiles_object *object =
 		container_of(_object, struct cachefiles_object, fscache);
+	int u;
 
 	_enter("{OBJ%x,%d}", _object->debug_id, atomic_read(&object->usage));
 
 #ifdef CACHEFILES_DEBUG_SLAB
 	ASSERT((atomic_read(&object->usage) & 0xffff0000) != 0x6b6b0000);
 #endif
 
-	atomic_inc(&object->usage);
+	u = atomic_inc_return(&object->usage);
+	trace_cachefiles_ref(object, _object->cookie,
+			     (enum cachefiles_obj_ref_trace)why, u);
 	return &object->fscache;
 }
 
@@ -309,10 +313,12 @@ static void cachefiles_drop_object(struct fscache_object *_object)
 /*
  * dispose of a reference to an object
  */
-static void cachefiles_put_object(struct fscache_object *_object)
+static void cachefiles_put_object(struct fscache_object *_object,
+				  enum fscache_obj_ref_trace why)
 {
 	struct cachefiles_object *object;
 	struct fscache_cache *cache;
+	int u;
 
 	ASSERT(_object);
 
@@ -328,7 +334,11 @@ static void cachefiles_put_object(struct fscache_object *_object)
 	ASSERTIFCMP(object->fscache.parent,
 		    object->fscache.parent->n_children, >, 0);
 
-	if (atomic_dec_and_test(&object->usage)) {
+	u = atomic_dec_return(&object->usage);
+	trace_cachefiles_ref(object, _object->cookie,
+			     (enum cachefiles_obj_ref_trace)why, u);
+	ASSERTCMP(u, !=, -1);
+	if (u == 0) {
 		_debug("- kill object OBJ%x", object->fscache.debug_id);
 
 		ASSERT(!test_bit(CACHEFILES_OBJECT_ACTIVE, &object->flags));

fs/cachefiles/internal.h

@@ -124,6 +124,8 @@ struct cachefiles_xattr {
 	uint8_t				data[];
 };
 
+#include <trace/events/cachefiles.h>
+
 /*
  * note change of state for daemon
  */

fs/cachefiles/main.c

@@ -22,6 +22,7 @@
 #include <linux/statfs.h>
 #include <linux/sysctl.h>
 #include <linux/miscdevice.h>
+#define CREATE_TRACE_POINTS
 #include "internal.h"
 
 unsigned cachefiles_debug;

fs/cachefiles/namei.c

@@ -120,6 +120,7 @@ static void cachefiles_mark_object_buried(struct cachefiles_cache *cache,
 	}
 
 	write_unlock(&cache->active_lock);
+	trace_cachefiles_mark_buried(NULL, dentry, why);
 	_leave(" [no owner]");
 	return;
 
@@ -130,6 +131,8 @@ static void cachefiles_mark_object_buried(struct cachefiles_cache *cache,
 	       object->fscache.state->name,
 	       dentry);
 
+	trace_cachefiles_mark_buried(object, dentry, why);
+
 	if (fscache_object_is_live(&object->fscache)) {
 		pr_err("\n");
 		pr_err("Error: Can't preemptively bury live object\n");
@@ -158,13 +161,15 @@ static int cachefiles_mark_object_active(struct cachefiles_cache *cache,
 try_again:
 	write_lock(&cache->active_lock);
 
+	dentry = object->dentry;
+	trace_cachefiles_mark_active(object, dentry);
+
 	if (test_and_set_bit(CACHEFILES_OBJECT_ACTIVE, &object->flags)) {
 		pr_err("Error: Object already active\n");
 		cachefiles_printk_object(object, NULL);
 		BUG();
 	}
 
-	dentry = object->dentry;
 	_p = &cache->active_nodes.rb_node;
 	while (*_p) {
 		_parent = *_p;
@@ -191,6 +196,8 @@ static int cachefiles_mark_object_active(struct cachefiles_cache *cache,
 	/* an old object from a previous incarnation is hogging the slot - we
 	 * need to wait for it to be destroyed */
 wait_for_old_object:
+	trace_cachefiles_wait_active(object, dentry, xobject);
+
 	if (fscache_object_is_live(&xobject->fscache)) {
 		pr_err("\n");
 		pr_err("Error: Unexpected object collision\n");
@@ -248,12 +255,12 @@ static int cachefiles_mark_object_active(struct cachefiles_cache *cache,
 
 	ASSERT(!test_bit(CACHEFILES_OBJECT_ACTIVE, &xobject->flags));
 
-	cache->cache.ops->put_object(&xobject->fscache);
+	cache->cache.ops->put_object(&xobject->fscache, cachefiles_obj_put_wait_retry);
 	goto try_again;
 
 requeue:
 	clear_bit(CACHEFILES_OBJECT_ACTIVE, &object->flags);
-	cache->cache.ops->put_object(&xobject->fscache);
+	cache->cache.ops->put_object(&xobject->fscache, cachefiles_obj_put_wait_timeo);
 	_leave(" = -ETIMEDOUT");
 	return -ETIMEDOUT;
 }
@@ -265,6 +272,11 @@ void cachefiles_mark_object_inactive(struct cachefiles_cache *cache,
 				     struct cachefiles_object *object,
 				     blkcnt_t i_blocks)
 {
+	struct dentry *dentry = object->dentry;
+	struct inode *inode = d_backing_inode(dentry);
+
+	trace_cachefiles_mark_inactive(object, dentry, inode);
+
 	write_lock(&cache->active_lock);
 	rb_erase(&object->active_node, &cache->active_nodes);
 	clear_bit(CACHEFILES_OBJECT_ACTIVE, &object->flags);
@@ -288,6 +300,7 @@ void cachefiles_mark_object_inactive(struct cachefiles_cache *cache,
  * - unlocks the directory mutex
  */
 static int cachefiles_bury_object(struct cachefiles_cache *cache,
+				  struct cachefiles_object *object,
 				  struct dentry *dir,
 				  struct dentry *rep,
 				  bool preemptive,
@@ -312,6 +325,7 @@ static int cachefiles_bury_object(struct cachefiles_cache *cache,
 		if (ret < 0) {
 			cachefiles_io_error(cache, "Unlink security error");
 		} else {
+			trace_cachefiles_unlink(object, rep, why);
 			ret = vfs_unlink(d_inode(dir), rep, NULL);
 
 			if (preemptive)
@@ -413,6 +427,7 @@ static int cachefiles_bury_object(struct cachefiles_cache *cache,
 	if (ret < 0) {
 		cachefiles_io_error(cache, "Rename security error %d", ret);
 	} else {
+		trace_cachefiles_rename(object, rep, grave, why);
 		ret = vfs_rename(d_inode(dir), rep,
 				 d_inode(cache->graveyard), grave, NULL, 0);
 		if (ret != 0 && ret != -ENOMEM)
@@ -458,7 +473,7 @@ int cachefiles_delete_object(struct cachefiles_cache *cache,
 		/* we need to check that our parent is _still_ our parent - it
 		 * may have been renamed */
 		if (dir == object->dentry->d_parent) {
-			ret = cachefiles_bury_object(cache, dir,
+			ret = cachefiles_bury_object(cache, object, dir,
 						     object->dentry, false,
 						     FSCACHE_OBJECT_WAS_RETIRED);
 		} else {
@@ -486,6 +501,7 @@ int cachefiles_walk_to_object(struct cachefiles_object *parent,
 {
 	struct cachefiles_cache *cache;
 	struct dentry *dir, *next = NULL;
+	struct inode *inode;
 	struct path path;
 	unsigned long start;
 	const char *name;
@@ -529,13 +545,17 @@ int cachefiles_walk_to_object(struct cachefiles_object *parent,
 	start = jiffies;
 	next = lookup_one_len(name, dir, nlen);
 	cachefiles_hist(cachefiles_lookup_histogram, start);
-	if (IS_ERR(next))
+	if (IS_ERR(next)) {
+		trace_cachefiles_lookup(object, next, NULL);
 		goto lookup_error;
+	}
 
-	_debug("next -> %p %s", next, d_backing_inode(next) ? "positive" : "negative");
+	inode = d_backing_inode(next);
+	trace_cachefiles_lookup(object, next, inode);
+	_debug("next -> %p %s", next, inode ? "positive" : "negative");
 
 	if (!key)
-		object->new = !d_backing_inode(next);
+		object->new = !inode;
 
 	/* if this element of the path doesn't exist, then the lookup phase
 	 * failed, and we can release any readers in the certain knowledge that
@@ -558,6 +578,8 @@ int cachefiles_walk_to_object(struct cachefiles_object *parent,
 			start = jiffies;
 			ret = vfs_mkdir(d_inode(dir), next, 0);
 			cachefiles_hist(cachefiles_mkdir_histogram, start);
+			if (!key)
+				trace_cachefiles_mkdir(object, next, ret);
 			if (ret < 0)
 				goto create_error;
 
@@ -587,6 +609,7 @@ int cachefiles_walk_to_object(struct cachefiles_object *parent,
 			start = jiffies;
 			ret = vfs_create(d_inode(dir), next, S_IFREG, true);
 			cachefiles_hist(cachefiles_create_histogram, start);
+			trace_cachefiles_create(object, next, ret);
 			if (ret < 0)
 				goto create_error;
 
@@ -629,7 +652,8 @@ int cachefiles_walk_to_object(struct cachefiles_object *parent,
 			 * mutex) */
 			object->dentry = NULL;
 
-			ret = cachefiles_bury_object(cache, dir, next, true,
+			ret = cachefiles_bury_object(cache, object, dir, next,
+						     true,
 						     FSCACHE_OBJECT_IS_STALE);
 			dput(next);
 			next = NULL;
@@ -955,7 +979,7 @@ int cachefiles_cull(struct cachefiles_cache *cache, struct dentry *dir,
 	/*  actually remove the victim (drops the dir mutex) */
 	_debug("bury");
 
-	ret = cachefiles_bury_object(cache, dir, victim, false,
+	ret = cachefiles_bury_object(cache, NULL, dir, victim, false,
 				     FSCACHE_OBJECT_WAS_CULLED);
 	if (ret < 0)
 		goto error;

fs/fscache/cookie.c

@@ -101,7 +101,7 @@ struct fscache_cookie *__fscache_acquire_cookie(
 	 */
 	atomic_set(&cookie->n_active, 1);
 
-	atomic_inc(&parent->usage);
+	fscache_cookie_get(parent, fscache_cookie_get_acquire_parent);
 	atomic_inc(&parent->n_children);
 
 	cookie->def		= def;
@@ -125,6 +125,8 @@ struct fscache_cookie *__fscache_acquire_cookie(
 		break;
 	}
 
+	trace_fscache_acquire(cookie);
+
 	if (enable) {
 		/* if the object is an index then we need do nothing more here
 		 * - we create indices on disk when we need them as an index
@@ -134,7 +136,8 @@ struct fscache_cookie *__fscache_acquire_cookie(
 				set_bit(FSCACHE_COOKIE_ENABLED, &cookie->flags);
 			} else {
 				atomic_dec(&parent->n_children);
-				__fscache_cookie_put(cookie);
+				fscache_cookie_put(cookie,
+						   fscache_cookie_put_acquire_nobufs);
 				fscache_stat(&fscache_n_acquires_nobufs);
 				_leave(" = NULL");
 				return NULL;
@@ -159,6 +162,8 @@ void __fscache_enable_cookie(struct fscache_cookie *cookie,
 {
 	_enter("%p", cookie);
 
+	trace_fscache_enable(cookie);
+
 	wait_on_bit_lock(&cookie->flags, FSCACHE_COOKIE_ENABLEMENT_LOCK,
 			 TASK_UNINTERRUPTIBLE);
 
@@ -318,7 +323,7 @@ static int fscache_alloc_object(struct fscache_cache *cache,
 	 * attached to the cookie */
 	if (fscache_attach_object(cookie, object) < 0) {
 		fscache_stat(&fscache_n_cop_put_object);
-		cache->ops->put_object(object);
+		cache->ops->put_object(object, fscache_obj_put_attach_fail);
 		fscache_stat_d(&fscache_n_cop_put_object);
 	}
 
@@ -338,7 +343,7 @@ static int fscache_alloc_object(struct fscache_cache *cache,
 
 error_put:
 	fscache_stat(&fscache_n_cop_put_object);
-	cache->ops->put_object(object);
+	cache->ops->put_object(object, fscache_obj_put_alloc_fail);
 	fscache_stat_d(&fscache_n_cop_put_object);
 error:
 	_leave(" = %d", ret);
@@ -398,7 +403,7 @@ static int fscache_attach_object(struct fscache_cookie *cookie,
 
 	/* attach to the cookie */
 	object->cookie = cookie;
-	atomic_inc(&cookie->usage);
+	fscache_cookie_get(cookie, fscache_cookie_get_attach_object);
 	hlist_add_head(&object->cookie_link, &cookie->backing_objects);
 
 	fscache_objlist_add(object);
@@ -516,6 +521,8 @@ void __fscache_disable_cookie(struct fscache_cookie *cookie, bool invalidate)
 
 	_enter("%p,%u", cookie, invalidate);
 
+	trace_fscache_disable(cookie);
+
 	ASSERTCMP(atomic_read(&cookie->n_active), >, 0);
 
 	if (atomic_read(&cookie->n_children) != 0) {
@@ -601,6 +608,8 @@ void __fscache_relinquish_cookie(struct fscache_cookie *cookie, bool retire)
 	       cookie, cookie->def->name, cookie->netfs_data,
 	       atomic_read(&cookie->n_active), retire);
 
+	trace_fscache_relinquish(cookie, retire);
+
 	/* No further netfs-accessing operations on this cookie permitted */
 	if (test_and_set_bit(FSCACHE_COOKIE_RELINQUISHED, &cookie->flags))
 		BUG();
@@ -620,35 +629,38 @@ void __fscache_relinquish_cookie(struct fscache_cookie *cookie, bool retire)
 
 	/* Dispose of the netfs's link to the cookie */
 	ASSERTCMP(atomic_read(&cookie->usage), >, 0);
-	fscache_cookie_put(cookie);
+	fscache_cookie_put(cookie, fscache_cookie_put_relinquish);
 
 	_leave("");
 }
 EXPORT_SYMBOL(__fscache_relinquish_cookie);
 
 /*
- * destroy a cookie
+ * Drop a reference to a cookie.
  */
-void __fscache_cookie_put(struct fscache_cookie *cookie)
+void fscache_cookie_put(struct fscache_cookie *cookie,
+			enum fscache_cookie_trace where)
 {
 	struct fscache_cookie *parent;
+	int usage;
 
 	_enter("%p", cookie);
 
-	for (;;) {
-		_debug("FREE COOKIE %p", cookie);
+	do {
+		usage = atomic_dec_return(&cookie->usage);
+		trace_fscache_cookie(cookie, where, usage);
+
+		if (usage > 0)
+			return;
+		BUG_ON(usage < 0);
+
 		parent = cookie->parent;
 		BUG_ON(!hlist_empty(&cookie->backing_objects));
 		kmem_cache_free(fscache_cookie_jar, cookie);
 
-		if (!parent)
-			break;
-
 		cookie = parent;
-		BUG_ON(atomic_read(&cookie->usage) <= 0);
-		if (!atomic_dec_and_test(&cookie->usage))
-			break;
-	}
+		where = fscache_cookie_put_parent;
+	} while (cookie);
 
 	_leave("");
 }