From d0e27b7808dc667f3015be0b6888f6d680e222c8 Mon Sep 17 00:00:00 2001
From: David Howells <dhowells@redhat.com>
Date: Thu, 19 Nov 2009 18:12:02 +0000
Subject: CacheFiles: Better showing of debugging information in active object
 problems

Show more debugging information if cachefiles_mark_object_active() is asked to
activate an active object.

This may happen, for instance, if the netfs tries to register an object with
the same key multiple times.

The code is changed to (a) get the appropriate object lock to protect the
cookie pointer whilst we dereference it, and (b) get and display the cookie key
if available.

Signed-off-by: David Howells <dhowells@redhat.com>
---
 fs/cachefiles/namei.c | 102 +++++++++++++++++++++++++++++++++++++-------------
 1 file changed, 75 insertions(+), 27 deletions(-)

diff --git a/fs/cachefiles/namei.c b/fs/cachefiles/namei.c
index 3df86952ca64..00a0cda8f47a 100644
--- a/fs/cachefiles/namei.c
+++ b/fs/cachefiles/namei.c
@@ -27,6 +27,76 @@ static int cachefiles_wait_bit(void *flags)
 	return 0;
 }
 
+#define CACHEFILES_KEYBUF_SIZE 512
+
+/*
+ * dump debugging info about an object
+ */
+static noinline
+void __cachefiles_printk_object(struct cachefiles_object *object,
+				const char *prefix,
+				u8 *keybuf)
+{
+	struct fscache_cookie *cookie;
+	unsigned keylen, loop;
+
+	printk(KERN_ERR "%sobject: OBJ%x\n",
+	       prefix, object->fscache.debug_id);
+	printk(KERN_ERR "%sobjstate=%s fl=%lx swfl=%lx ev=%lx[%lx]\n",
+	       prefix, fscache_object_states[object->fscache.state],
+	       object->fscache.flags, object->fscache.work.flags,
+	       object->fscache.events,
+	       object->fscache.event_mask & FSCACHE_OBJECT_EVENTS_MASK);
+	printk(KERN_ERR "%sops=%u inp=%u exc=%u\n",
+	       prefix, object->fscache.n_ops, object->fscache.n_in_progress,
+	       object->fscache.n_exclusive);
+	printk(KERN_ERR "%sparent=%p\n",
+	       prefix, object->fscache.parent);
+
+	spin_lock(&object->fscache.lock);
+	cookie = object->fscache.cookie;
+	if (cookie) {
+		printk(KERN_ERR "%scookie=%p [pr=%p nd=%p fl=%lx]\n",
+		       prefix,
+		       object->fscache.cookie,
+		       object->fscache.cookie->parent,
+		       object->fscache.cookie->netfs_data,
+		       object->fscache.cookie->flags);
+		if (keybuf)
+			keylen = cookie->def->get_key(cookie->netfs_data, keybuf,
+						      CACHEFILES_KEYBUF_SIZE);
+		else
+			keylen = 0;
+	} else {
+		printk(KERN_ERR "%scookie=NULL\n", prefix);
+		keylen = 0;
+	}
+	spin_unlock(&object->fscache.lock);
+
+	if (keylen) {
+		printk(KERN_ERR "%skey=[%u] '", prefix, keylen);
+		for (loop = 0; loop < keylen; loop++)
+			printk("%02x", keybuf[loop]);
+		printk("'\n");
+	}
+}
+
+/*
+ * dump debugging info about a pair of objects
+ */
+static noinline void cachefiles_printk_object(struct cachefiles_object *object,
+					      struct cachefiles_object *xobject)
+{
+	u8 *keybuf;
+
+	keybuf = kmalloc(CACHEFILES_KEYBUF_SIZE, GFP_NOIO);
+	if (object)
+		__cachefiles_printk_object(object, "", keybuf);
+	if (xobject)
+		__cachefiles_printk_object(xobject, "x", keybuf);
+	kfree(keybuf);
+}
+
 /*
  * record the fact that an object is now active
  */
@@ -42,8 +112,11 @@ static void cachefiles_mark_object_active(struct cachefiles_cache *cache,
 try_again:
 	write_lock(&cache->active_lock);
 
-	if (test_and_set_bit(CACHEFILES_OBJECT_ACTIVE, &object->flags))
+	if (test_and_set_bit(CACHEFILES_OBJECT_ACTIVE, &object->flags)) {
+		printk(KERN_ERR "CacheFiles: Error: Object already active\n");
+		cachefiles_printk_object(object, NULL);
 		BUG();
+	}
 
 	dentry = object->dentry;
 	_p = &cache->active_nodes.rb_node;
@@ -76,32 +149,7 @@ wait_for_old_object:
 		printk(KERN_ERR "\n");
 		printk(KERN_ERR "CacheFiles: Error:"
 		       " Unexpected object collision\n");
-		printk(KERN_ERR "xobject: OBJ%x\n",
-		       xobject->fscache.debug_id);
-		printk(KERN_ERR "xobjstate=%s\n",
-		       fscache_object_states[xobject->fscache.state]);
-		printk(KERN_ERR "xobjflags=%lx\n", xobject->fscache.flags);
-		printk(KERN_ERR "xobjevent=%lx [%lx]\n",
-		       xobject->fscache.events, xobject->fscache.event_mask);
-		printk(KERN_ERR "xops=%u inp=%u exc=%u\n",
-		       xobject->fscache.n_ops, xobject->fscache.n_in_progress,
-		       xobject->fscache.n_exclusive);
-		printk(KERN_ERR "xcookie=%p [pr=%p nd=%p fl=%lx]\n",
-		       xobject->fscache.cookie,
-		       xobject->fscache.cookie->parent,
-		       xobject->fscache.cookie->netfs_data,
-		       xobject->fscache.cookie->flags);
-		printk(KERN_ERR "xparent=%p\n",
-		       xobject->fscache.parent);
-		printk(KERN_ERR "object: OBJ%x\n",
-		       object->fscache.debug_id);
-		printk(KERN_ERR "cookie=%p [pr=%p nd=%p fl=%lx]\n",
-		       object->fscache.cookie,
-		       object->fscache.cookie->parent,
-		       object->fscache.cookie->netfs_data,
-		       object->fscache.cookie->flags);
-		printk(KERN_ERR "parent=%p\n",
-		       object->fscache.parent);
+		cachefiles_printk_object(object, xobject);
 		BUG();
 	}
 	atomic_inc(&xobject->usage);
-- 
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