fscache: Add a cookie debug ID and use that in traces

Add a cookie debug ID and use that in traces and in procfiles rather than
displaying the (hashed) pointer to the cookie.  This is easier to correlate
and we don't lose anything when interpreting oops output since that shows
unhashed addresses and registers that aren't comparable to the hashed
values.

Changes:

ver #2:
 - Fix the fscache_op tracepoint to handle a NULL cookie pointer.

Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Jeff Layton <jlayton@redhat.com>
cc: linux-cachefs@redhat.com
Link: https://lore.kernel.org/r/158861210988.340223.11688464116498247790.stgit@warthog.procyon.org.uk/ # rfc
Link: https://lore.kernel.org/r/159465769844.1376105.14119502774019865432.stgit@warthog.procyon.org.uk/
Link: https://lore.kernel.org/r/160588459097.3465195.1273313637721852165.stgit@warthog.procyon.org.uk/ # rfc
Link: https://lore.kernel.org/r/162431193544.2908479.17556704572948300790.stgit@warthog.procyon.org.uk/

3 files changed, 28 insertions, 16 deletions

diff --git a/fs/fscache/cookie.c b/fs/fscache/cookie.c
index 751bc5b1cddf..f2be98d2c64d 100644
--- a/fs/fscache/cookie.c
+++ b/fs/fscache/cookie.c
@@ -29,21 +29,29 @@ static int fscache_attach_object(struct fscache_cookie *cookie,
 
 static void fscache_print_cookie(struct fscache_cookie *cookie, char prefix)
 {
-	struct hlist_node *object;
+	struct fscache_object *object;
+	struct hlist_node *o;
 	const u8 *k;
 	unsigned loop;
 
-	pr_err("%c-cookie c=%p [p=%p fl=%lx nc=%u na=%u]\n",
-	       prefix, cookie, cookie->parent, cookie->flags,
+	pr_err("%c-cookie c=%08x [p=%08x fl=%lx nc=%u na=%u]\n",
+	       prefix,
+	       cookie->debug_id,
+	       cookie->parent ? cookie->parent->debug_id : 0,
+	       cookie->flags,
 	       atomic_read(&cookie->n_children),
 	       atomic_read(&cookie->n_active));
-	pr_err("%c-cookie d=%p n=%p\n",
-	       prefix, cookie->def, cookie->netfs_data);
+	pr_err("%c-cookie d=%p{%s} n=%p\n",
+	       prefix,
+	       cookie->def,
+	       cookie->def ? cookie->def->name : "?",
+	       cookie->netfs_data);
 
-	object = READ_ONCE(cookie->backing_objects.first);
-	if (object)
-		pr_err("%c-cookie o=%p\n",
-		       prefix, hlist_entry(object, struct fscache_object, cookie_link));
+	o = READ_ONCE(cookie->backing_objects.first);
+	if (o) {
+		object = hlist_entry(o, struct fscache_object, cookie_link);
+		pr_err("%c-cookie o=%u\n", prefix, object->debug_id);
+	}
 
 	pr_err("%c-key=[%u] '", prefix, cookie->key_len);
 	k = (cookie->key_len <= sizeof(cookie->inline_key)) ?
@@ -129,6 +137,8 @@ static long fscache_compare_cookie(const struct fscache_cookie *a,
 	return memcmp(ka, kb, a->key_len);
 }
 
+static atomic_t fscache_cookie_debug_id = ATOMIC_INIT(1);
+
 /*
  * Allocate a cookie.
  */
@@ -163,6 +173,7 @@ struct fscache_cookie *fscache_alloc_cookie(
 
 	atomic_set(&cookie->usage, 1);
 	atomic_set(&cookie->n_children, 0);
+	cookie->debug_id = atomic_inc_return(&fscache_cookie_debug_id);
 
 	/* We keep the active count elevated until relinquishment to prevent an
 	 * attempt to wake up every time the object operations queue quiesces.
diff --git a/fs/fscache/fsdef.c b/fs/fscache/fsdef.c
index 09ed8795ad86..5f8f6fe243fe 100644
--- a/fs/fscache/fsdef.c
+++ b/fs/fscache/fsdef.c
@@ -45,6 +45,7 @@ static struct fscache_cookie_def fscache_fsdef_index_def = {
 };
 
 struct fscache_cookie fscache_fsdef_index = {
+	.debug_id	= 1,
 	.usage		= ATOMIC_INIT(1),
 	.n_active	= ATOMIC_INIT(1),
 	.lock		= __SPIN_LOCK_UNLOCKED(fscache_fsdef_index.lock),
diff --git a/fs/fscache/object-list.c b/fs/fscache/object-list.c
index e106a1a1600d..1a0dc32c0a33 100644
--- a/fs/fscache/object-list.c
+++ b/fs/fscache/object-list.c
@@ -170,7 +170,7 @@ static int fscache_objlist_show(struct seq_file *m, void *v)
 	if ((unsigned long) v == 1) {
 		seq_puts(m, "OBJECT   PARENT   STAT CHLDN OPS OOP IPR EX READS"
 			 " EM EV FL S"
-			 " | NETFS_COOKIE_DEF TY FL NETFS_DATA");
+			 " | COOKIE   NETFS_COOKIE_DEF TY FL NETFS_DATA");
 		if (config & (FSCACHE_OBJLIST_CONFIG_KEY |
 			      FSCACHE_OBJLIST_CONFIG_AUX))
 			seq_puts(m, "       ");
@@ -189,7 +189,7 @@ static int fscache_objlist_show(struct seq_file *m, void *v)
 	if ((unsigned long) v == 2) {
 		seq_puts(m, "======== ======== ==== ===== === === === == ====="
 			 " == == == ="
-			 " | ================ == == ================");
+			 " | ======== ================ == === ================");
 		if (config & (FSCACHE_OBJLIST_CONFIG_KEY |
 			      FSCACHE_OBJLIST_CONFIG_AUX))
 			seq_puts(m, " ================");
@@ -231,9 +231,9 @@ static int fscache_objlist_show(struct seq_file *m, void *v)
 	}
 
 	seq_printf(m,
-		   "%8x %8x %s %5u %3u %3u %3u %2u %5u %2lx %2lx %2lx %1x | ",
+		   "%08x %08x %s %5u %3u %3u %3u %2u %5u %2lx %2lx %2lx %1x | ",
 		   obj->debug_id,
-		   obj->parent ? obj->parent->debug_id : -1,
+		   obj->parent ? obj->parent->debug_id : UINT_MAX,
 		   obj->state->short_name,
 		   obj->n_children,
 		   obj->n_ops,
@@ -246,7 +246,7 @@ static int fscache_objlist_show(struct seq_file *m, void *v)
 		   obj->flags,
 		   work_busy(&obj->work));
 
-	if (fscache_use_cookie(obj)) {
+	if (obj->cookie) {
 		uint16_t keylen = 0, auxlen = 0;
 
 		switch (cookie->type) {
@@ -263,7 +263,8 @@ static int fscache_objlist_show(struct seq_file *m, void *v)
 			break;
 		}
 
-		seq_printf(m, "%-16s %s %2lx %16p",
+		seq_printf(m, "%08x %-16s %s %3lx %16p",
+			   cookie->debug_id,
 			   cookie->def->name,
 			   type,
 			   cookie->flags,
@@ -292,7 +293,6 @@ static int fscache_objlist_show(struct seq_file *m, void *v)
 		}
 
 		seq_puts(m, "\n");
-		fscache_unuse_cookie(obj);
 	} else {
 		seq_puts(m, "<no_netfs>\n");
 	}