afs: Improve afs_volume tracing to display a debug ID

Improve the tracing of afs_volume objects to include displaying a debug ID
so that different instances of volumes with the same "vid" can be
distinguished.

Also be consistent about displaying the volume's refcount (and not the
cell's).

Signed-off-by: David Howells <dhowells@redhat.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org
cc: linux-fsdevel@vger.kernel.org
Link: https://lore.kernel.org/r/20250224234154.2014840-9-dhowells@redhat.com/ # v1
Link: https://lore.kernel.org/r/20250310094206.801057-5-dhowells@redhat.com/ # v4

Author: dhowells

fs/afs/internal.h

@@ -623,6 +623,7 @@ struct afs_volume {
 	afs_volid_t		vid;		/* The volume ID of this volume */
 	afs_volid_t		vids[AFS_MAXTYPES]; /* All associated volume IDs */
 	refcount_t		ref;
+	unsigned int		debug_id;	/* Debugging ID for traces */
 	time64_t		update_at;	/* Time at which to next update */
 	struct afs_cell		*cell;		/* Cell to which belongs (pins ref) */
 	struct rb_node		cell_node;	/* Link in cell->volumes */

fs/afs/volume.c

@@ -10,6 +10,7 @@
 #include "internal.h"
 
 static unsigned __read_mostly afs_volume_record_life = 60 * 60;
+static atomic_t afs_volume_debug_id;
 
 static void afs_destroy_volume(struct work_struct *work);
 
@@ -59,7 +60,7 @@ static void afs_remove_volume_from_cell(struct afs_volume *volume)
 	struct afs_cell *cell = volume->cell;
 
 	if (!hlist_unhashed(&volume->proc_link)) {
-		trace_afs_volume(volume->vid, refcount_read(&cell->ref),
+		trace_afs_volume(volume->debug_id, volume->vid, refcount_read(&volume->ref),
 				 afs_volume_trace_remove);
 		write_seqlock(&cell->volume_lock);
 		hlist_del_rcu(&volume->proc_link);
@@ -84,6 +85,7 @@ static struct afs_volume *afs_alloc_volume(struct afs_fs_context *params,
 	if (!volume)
 		goto error_0;
 
+	volume->debug_id	= atomic_inc_return(&afs_volume_debug_id);
 	volume->vid		= vldb->vid[params->type];
 	volume->update_at	= ktime_get_real_seconds() + afs_volume_record_life;
 	volume->cell		= afs_get_cell(params->cell, afs_cell_trace_get_vol);
@@ -115,7 +117,7 @@ static struct afs_volume *afs_alloc_volume(struct afs_fs_context *params,
 
 	*_slist = slist;
 	rcu_assign_pointer(volume->servers, slist);
-	trace_afs_volume(volume->vid, 1, afs_volume_trace_alloc);
+	trace_afs_volume(volume->debug_id, volume->vid, 1, afs_volume_trace_alloc);
 	return volume;
 
 error_1:
@@ -247,7 +249,7 @@ static void afs_destroy_volume(struct work_struct *work)
 	afs_remove_volume_from_cell(volume);
 	afs_put_serverlist(volume->cell->net, slist);
 	afs_put_cell(volume->cell, afs_cell_trace_put_vol);
-	trace_afs_volume(volume->vid, refcount_read(&volume->ref),
+	trace_afs_volume(volume->debug_id, volume->vid, refcount_read(&volume->ref),
 			 afs_volume_trace_free);
 	kfree_rcu(volume, rcu);
 
@@ -262,7 +264,7 @@ bool afs_try_get_volume(struct afs_volume *volume, enum afs_volume_trace reason)
 	int r;
 
 	if (__refcount_inc_not_zero(&volume->ref, &r)) {
-		trace_afs_volume(volume->vid, r + 1, reason);
+		trace_afs_volume(volume->debug_id, volume->vid, r + 1, reason);
 		return true;
 	}
 	return false;
@@ -278,7 +280,7 @@ struct afs_volume *afs_get_volume(struct afs_volume *volume,
 		int r;
 
 		__refcount_inc(&volume->ref, &r);
-		trace_afs_volume(volume->vid, r + 1, reason);
+		trace_afs_volume(volume->debug_id, volume->vid, r + 1, reason);
 	}
 	return volume;
 }
@@ -290,12 +292,13 @@ struct afs_volume *afs_get_volume(struct afs_volume *volume,
 void afs_put_volume(struct afs_volume *volume, enum afs_volume_trace reason)
 {
 	if (volume) {
+		unsigned int debug_id = volume->debug_id;
 		afs_volid_t vid = volume->vid;
 		bool zero;
 		int r;
 
 		zero = __refcount_dec_and_test(&volume->ref, &r);
-		trace_afs_volume(vid, r - 1, reason);
+		trace_afs_volume(debug_id, vid, r - 1, reason);
 		if (zero)
 			schedule_work(&volume->destructor);
 	}

include/trace/events/afs.h

@@ -1539,25 +1539,29 @@ TRACE_EVENT(afs_server,
 	    );
 
 TRACE_EVENT(afs_volume,
-	    TP_PROTO(afs_volid_t vid, int ref, enum afs_volume_trace reason),
+	    TP_PROTO(unsigned int debug_id, afs_volid_t vid, int ref,
+		     enum afs_volume_trace reason),
 
-	    TP_ARGS(vid, ref, reason),
+	    TP_ARGS(debug_id, vid, ref, reason),
 
 	    TP_STRUCT__entry(
+		    __field(unsigned int,		debug_id)
 		    __field(afs_volid_t,		vid)
 		    __field(int,			ref)
 		    __field(enum afs_volume_trace,	reason)
 			     ),
 
 	    TP_fast_assign(
-		    __entry->vid = vid;
-		    __entry->ref = ref;
-		    __entry->reason = reason;
+		    __entry->debug_id	= debug_id;
+		    __entry->vid	= vid;
+		    __entry->ref	= ref;
+		    __entry->reason	= reason;
 			   ),
 
-	    TP_printk("V=%llx %s ur=%d",
-		      __entry->vid,
+	    TP_printk("V=%08x %s vid=%llx r=%d",
+		      __entry->debug_id,
 		      __print_symbolic(__entry->reason, afs_volume_traces),
+		      __entry->vid,
 		      __entry->ref)
 	    );