Merge tag 'afs-fixes-20220802' of git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs

Pull AFS fixes from David Howells:
 "Fix AFS refcount handling.

  The first patch converts afs to use refcount_t for its refcounts and
  the second patch fixes afs_put_call() and afs_put_server() to save the
  values they're going to log in the tracepoint before decrementing the
  refcount"

* tag 'afs-fixes-20220802' of git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs:
  afs: Fix access after dec in put functions
  afs: Use refcount_t rather than atomic_t

1 files changed, 13 insertions, 8 deletions

diff --git a/fs/afs/volume.c b/fs/afs/volume.c
index cc665cef0abe..f4937029dcd7 100644
--- a/fs/afs/volume.c
+++ b/fs/afs/volume.c
@@ -52,7 +52,7 @@ 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, atomic_read(&volume->usage),
+		trace_afs_volume(volume->vid, refcount_read(&cell->ref),
 				 afs_volume_trace_remove);
 		write_seqlock(&cell->volume_lock);
 		hlist_del_rcu(&volume->proc_link);
@@ -87,7 +87,7 @@ static struct afs_volume *afs_alloc_volume(struct afs_fs_context *params,
 	volume->type_force	= params->force;
 	volume->name_len	= vldb->name_len;
 
-	atomic_set(&volume->usage, 1);
+	refcount_set(&volume->ref, 1);
 	INIT_HLIST_NODE(&volume->proc_link);
 	rwlock_init(&volume->servers_lock);
 	rwlock_init(&volume->cb_v_break_lock);
@@ -228,7 +228,7 @@ static void afs_destroy_volume(struct afs_net *net, struct afs_volume *volume)
 	afs_remove_volume_from_cell(volume);
 	afs_put_serverlist(net, rcu_access_pointer(volume->servers));
 	afs_put_cell(volume->cell, afs_cell_trace_put_vol);
-	trace_afs_volume(volume->vid, atomic_read(&volume->usage),
+	trace_afs_volume(volume->vid, refcount_read(&volume->ref),
 			 afs_volume_trace_free);
 	kfree_rcu(volume, rcu);
 
@@ -242,8 +242,10 @@ struct afs_volume *afs_get_volume(struct afs_volume *volume,
 				  enum afs_volume_trace reason)
 {
 	if (volume) {
-		int u = atomic_inc_return(&volume->usage);
-		trace_afs_volume(volume->vid, u, reason);
+		int r;
+
+		__refcount_inc(&volume->ref, &r);
+		trace_afs_volume(volume->vid, r + 1, reason);
 	}
 	return volume;
 }
@@ -257,9 +259,12 @@ void afs_put_volume(struct afs_net *net, struct afs_volume *volume,
 {
 	if (volume) {
 		afs_volid_t vid = volume->vid;
-		int u = atomic_dec_return(&volume->usage);
-		trace_afs_volume(vid, u, reason);
-		if (u == 0)
+		bool zero;
+		int r;
+
+		zero = __refcount_dec_and_test(&volume->ref, &r);
+		trace_afs_volume(vid, r - 1, reason);
+		if (zero)
 			afs_destroy_volume(net, volume);
 	}
 }