FAILED: patch "[PATCH] nfsd: close shrinker/GC/fsnotify vs per-net shutdown race in" failed to apply to 6.18-stable tree

index da5a44c31acb..1ea2bfd51825 100644
@@ -55,6 +55,17 @@
 /* We only care about NFSD_MAY_READ/WRITE for this cache */
 #define NFSD_FILE_MAY_MASK	(NFSD_MAY_READ|NFSD_MAY_WRITE|NFSD_MAY_LOCALIO)
 
+/* If the shrinker runs between calls to list_lru_walk_node() in
+ * nfsd_file_gc(), the "remaining" count will be wrong.  This could
+ * result in premature freeing of some files.  This may not matter much
+ * but is easy to fix with this spinlock which temporarily disables
+ * the shrinker.
+ *
+ * It also serializes callers of nfsd_file_dispose_list_delayed()
+ * against per-net shutdown.
+ */
+static DEFINE_SPINLOCK(nfsd_gc_lock);
+
 static DEFINE_PER_CPU(unsigned long, nfsd_file_cache_hits);
 static DEFINE_PER_CPU(unsigned long, nfsd_file_acquisitions);
 static DEFINE_PER_CPU(unsigned long, nfsd_file_allocations);

@@ -423,10 +434,16 @@ nfsd_file_dispose_list(struct list_head *dispose)
  * Transfers each file to the dispose list in its nfsd_net and wakes an nfsd
  * thread to do the actual close.  This keeps the cost of fput() in the nfsd
  * threads rather than in the shrinker or GC worker.
+ *
+ * All callers must hold nfsd_gc_lock, so that nfsd_file_cache_shutdown_net()
+ * can synchronize against them before draining the per-net dispose list.
+ * This guarantees nf_net is still live when we call net_generic().
  */
 static void
 nfsd_file_dispose_list_delayed(struct list_head *dispose)
 {
+	lockdep_assert_held(&nfsd_gc_lock);
+
 	while (!list_empty(dispose)) {
 		struct nfsd_file *nf = list_first_entry(dispose,
 						struct nfsd_file, nf_gc);

@@ -557,13 +574,6 @@ nfsd_file_gc_cb(struct list_head *item, struct list_lru_one *lru,
 	return nfsd_file_lru_cb(item, lru, arg);
 }
 
-/* If the shrinker runs between calls to list_lru_walk_node() in
- * nfsd_file_gc(), the "remaining" count will be wrong.  This could
- * result in premature freeing of some files.  This may not matter much
- * but is easy to fix with this spinlock which temporarily disables
- * the shrinker.
- */
-static DEFINE_SPINLOCK(nfsd_gc_lock);
 static void
 nfsd_file_gc(void)
 {

@@ -586,9 +596,9 @@ nfsd_file_gc(void)
 				remaining = 0;
 		}
 	}
+	nfsd_file_dispose_list_delayed(&dispose);
 	spin_unlock(&nfsd_gc_lock);
 	trace_nfsd_file_gc_removed(ret, list_lru_count(&nfsd_file_lru));
-	nfsd_file_dispose_list_delayed(&dispose);
 }
 
 static void

@@ -616,9 +626,9 @@ nfsd_file_lru_scan(struct shrinker *s, struct shrink_control *sc)
 
 	ret = list_lru_shrink_walk(&nfsd_file_lru, sc,
 				   nfsd_file_lru_cb, &dispose);
+	nfsd_file_dispose_list_delayed(&dispose);
 	spin_unlock(&nfsd_gc_lock);
 	trace_nfsd_file_shrinker_removed(ret, list_lru_count(&nfsd_file_lru));
-	nfsd_file_dispose_list_delayed(&dispose);
 	return ret;
 }
 

@@ -704,8 +714,10 @@ nfsd_file_close_inode(struct inode *inode)
 {
 	LIST_HEAD(dispose);
 
+	spin_lock(&nfsd_gc_lock);
 	nfsd_file_queue_for_close(inode, &dispose);
 	nfsd_file_dispose_list_delayed(&dispose);
+	spin_unlock(&nfsd_gc_lock);
 }
 
 /**

@@ -974,6 +986,14 @@ nfsd_file_cache_shutdown_net(struct net *net)
 	struct nfsd_net *nn = net_generic(net, nfsd_net_id);
 
 	nfsd_file_cache_purge(net);
+	/*
+	 * Ensure any in-progress shrinker, GC, or fsnotify/lease callback
+	 * (all of which hold nfsd_gc_lock while calling
+	 * nfsd_file_dispose_list_delayed()) has fully completed before
+	 * draining the per-net dispose list.
+	 */
+	spin_lock(&nfsd_gc_lock);
+	spin_unlock(&nfsd_gc_lock);
 	nfsd_file_dispose_list(&nn->fcache_dispose_list);
 }
 

index a238b6725008a..2258e7a59a850 100644
@@ -471,11 +471,20 @@ void nfsd_file_net_dispose(struct nfsd_net *nn)
 		for (i = 0; i < 8 && !list_empty(&l->freeme); i++)
 			list_move(l->freeme.next, &dispose);
 		spin_unlock(&l->lock);
-		if (!list_empty(&l->freeme))
-			/* Wake up another thread to share the work
+		if (!list_empty(&l->freeme)) {
+			/*
+			 * Wake up another thread to share the work
 			 * *before* doing any actual disposing.
+			 *
+			 * The filecache laundrette is shut down after
+			 * the nn->nfsd_serv pointer is cleared, but
+			 * before the svc_serv is freed.
 			 */
-			svc_wake_up(nn->nfsd_serv);
+			struct svc_serv *serv = nn->nfsd_serv;
+
+			if (serv)
+				svc_wake_up(serv);
+		}
 		nfsd_file_dispose_list(&dispose);
 	}
 }

index 2258e7a59a850..f8974d5fa6737 100644
@@ -62,11 +62,6 @@ static DEFINE_PER_CPU(unsigned long, nfsd_file_releases);
 static DEFINE_PER_CPU(unsigned long, nfsd_file_total_age);
 static DEFINE_PER_CPU(unsigned long, nfsd_file_evictions);
 
-struct nfsd_fcache_disposal {
-	spinlock_t lock;
-	struct list_head freeme;
-};
-
 static struct kmem_cache		*nfsd_file_slab;
 static struct kmem_cache		*nfsd_file_mark_slab;
 static struct list_lru			nfsd_file_lru;

@@ -419,25 +414,25 @@ nfsd_file_dispose_list(struct list_head *dispose)
 }
 
 /**
- * nfsd_file_dispose_list_delayed - move list of dead files to net's freeme list
+ * nfsd_file_dispose_list_delayed - queue dead files for nfsd thread disposal
  * @dispose: list of nfsd_files to be disposed
  *
- * Transfers each file to the "freeme" list for its nfsd_net, to eventually
- * be disposed of by the per-net garbage collector.
+ * Transfers each file to the dispose list in its nfsd_net and wakes an nfsd
+ * thread to do the actual close.  This keeps the cost of fput() in the nfsd
+ * threads rather than in the shrinker or GC worker.
  */
 static void
 nfsd_file_dispose_list_delayed(struct list_head *dispose)
 {
-	while(!list_empty(dispose)) {
+	while (!list_empty(dispose)) {
 		struct nfsd_file *nf = list_first_entry(dispose,
 						struct nfsd_file, nf_gc);
 		struct nfsd_net *nn = net_generic(nf->nf_net, nfsd_net_id);
-		struct nfsd_fcache_disposal *l = nn->fcache_disposal;
 		struct svc_serv *serv;
 
-		spin_lock(&l->lock);
-		list_move_tail(&nf->nf_gc, &l->freeme);
-		spin_unlock(&l->lock);
+		spin_lock(&nn->fcache_dispose_lock);
+		list_move_tail(&nf->nf_gc, &nn->fcache_dispose_list);
+		spin_unlock(&nn->fcache_dispose_lock);
 
 		/*
 		 * The filecache laundrette is shut down after the

@@ -461,17 +456,15 @@ nfsd_file_dispose_list_delayed(struct list_head *dispose)
  */
 void nfsd_file_net_dispose(struct nfsd_net *nn)
 {
-	struct nfsd_fcache_disposal *l = nn->fcache_disposal;
-
-	if (!list_empty(&l->freeme)) {
+	if (!list_empty(&nn->fcache_dispose_list)) {
 		LIST_HEAD(dispose);
 		int i;
 
-		spin_lock(&l->lock);
-		for (i = 0; i < 8 && !list_empty(&l->freeme); i++)
-			list_move(l->freeme.next, &dispose);
-		spin_unlock(&l->lock);
-		if (!list_empty(&l->freeme)) {
+		spin_lock(&nn->fcache_dispose_lock);
+		for (i = 0; i < 8 && !list_empty(&nn->fcache_dispose_list); i++)
+			list_move(nn->fcache_dispose_list.next, &dispose);
+		spin_unlock(&nn->fcache_dispose_lock);
+		if (!list_empty(&nn->fcache_dispose_list)) {
 			/*
 			 * Wake up another thread to share the work
 			 * *before* doing any actual disposing.

@@ -695,11 +688,11 @@ nfsd_file_queue_for_close(struct inode *inode, struct list_head *dispose)
 }
 
 /**
- * nfsd_file_close_inode - attempt a delayed close of a nfsd_file
+ * nfsd_file_close_inode - attempt a deferred close of a nfsd_file
  * @inode: inode of the file to attempt to remove
  *
  * Close out any open nfsd_files that can be reaped for @inode. The
- * actual freeing is deferred to the dispose_list_delayed infrastructure.
+ * actual freeing is deferred to the nfsd service threads.
  *
  * This is used by the fsnotify callbacks and setlease notifier.
  */

@@ -903,42 +896,14 @@ __nfsd_file_cache_purge(struct net *net)
 	nfsd_file_dispose_list(&dispose);
 }
 
-static struct nfsd_fcache_disposal *
-nfsd_alloc_fcache_disposal(void)
-{
-	struct nfsd_fcache_disposal *l;
-
-	l = kmalloc(sizeof(*l), GFP_KERNEL);
-	if (!l)
-		return NULL;
-	spin_lock_init(&l->lock);
-	INIT_LIST_HEAD(&l->freeme);
-	return l;
-}
-
-static void
-nfsd_free_fcache_disposal(struct nfsd_fcache_disposal *l)
-{
-	nfsd_file_dispose_list(&l->freeme);
-	kfree(l);
-}
-
-static void
-nfsd_free_fcache_disposal_net(struct net *net)
-{
-	struct nfsd_net *nn = net_generic(net, nfsd_net_id);
-	struct nfsd_fcache_disposal *l = nn->fcache_disposal;
-
-	nfsd_free_fcache_disposal(l);
-}
-
 int
 nfsd_file_cache_start_net(struct net *net)
 {
 	struct nfsd_net *nn = net_generic(net, nfsd_net_id);
 
-	nn->fcache_disposal = nfsd_alloc_fcache_disposal();
-	return nn->fcache_disposal ? 0 : -ENOMEM;
+	spin_lock_init(&nn->fcache_dispose_lock);
+	INIT_LIST_HEAD(&nn->fcache_dispose_list);
+	return 0;
 }
 
 /**

@@ -957,8 +922,10 @@ nfsd_file_cache_purge(struct net *net)
 void
 nfsd_file_cache_shutdown_net(struct net *net)
 {
+	struct nfsd_net *nn = net_generic(net, nfsd_net_id);
+
 	nfsd_file_cache_purge(net);
-	nfsd_free_fcache_disposal_net(net);
+	nfsd_file_dispose_list(&nn->fcache_dispose_list);
 }
 
 void

index fe8338735e7cc..2a2b65930e3a9 100644
@@ -200,7 +200,8 @@ struct nfsd_net {
 	/* utsname taken from the process that starts the server */
 	char			nfsd_name[UNX_MAXNODENAME+1];
 
-	struct nfsd_fcache_disposal *fcache_disposal;
+	spinlock_t		fcache_dispose_lock;
+	struct list_head	fcache_dispose_list;
 
 	siphash_key_t		siphash_key;
 

index f8974d5fa6737..cfa2b5ad656ac 100644
@@ -55,6 +55,17 @@
 /* We only care about NFSD_MAY_READ/WRITE for this cache */
 #define NFSD_FILE_MAY_MASK	(NFSD_MAY_READ|NFSD_MAY_WRITE|NFSD_MAY_LOCALIO)
 
+/* If the shrinker runs between calls to list_lru_walk_node() in
+ * nfsd_file_gc(), the "remaining" count will be wrong.  This could
+ * result in premature freeing of some files.  This may not matter much
+ * but is easy to fix with this spinlock which temporarily disables
+ * the shrinker.
+ *
+ * It also serializes callers of nfsd_file_dispose_list_delayed()
+ * against per-net shutdown.
+ */
+static DEFINE_SPINLOCK(nfsd_gc_lock);
+
 static DEFINE_PER_CPU(unsigned long, nfsd_file_cache_hits);
 static DEFINE_PER_CPU(unsigned long, nfsd_file_acquisitions);
 static DEFINE_PER_CPU(unsigned long, nfsd_file_allocations);

@@ -420,10 +431,16 @@ nfsd_file_dispose_list(struct list_head *dispose)
  * Transfers each file to the dispose list in its nfsd_net and wakes an nfsd
  * thread to do the actual close.  This keeps the cost of fput() in the nfsd
  * threads rather than in the shrinker or GC worker.
+ *
+ * All callers must hold nfsd_gc_lock, so that nfsd_file_cache_shutdown_net()
+ * can synchronize against them before draining the per-net dispose list.
+ * This guarantees nf_net is still live when we call net_generic().
  */
 static void
 nfsd_file_dispose_list_delayed(struct list_head *dispose)
 {
+	lockdep_assert_held(&nfsd_gc_lock);
+
 	while (!list_empty(dispose)) {
 		struct nfsd_file *nf = list_first_entry(dispose,
 						struct nfsd_file, nf_gc);

@@ -554,13 +571,6 @@ nfsd_file_gc_cb(struct list_head *item, struct list_lru_one *lru,
 	return nfsd_file_lru_cb(item, lru, arg);
 }
 
-/* If the shrinker runs between calls to list_lru_walk_node() in
- * nfsd_file_gc(), the "remaining" count will be wrong.  This could
- * result in premature freeing of some files.  This may not matter much
- * but is easy to fix with this spinlock which temporarily disables
- * the shrinker.
- */
-static DEFINE_SPINLOCK(nfsd_gc_lock);
 static void
 nfsd_file_gc(void)
 {

@@ -583,9 +593,9 @@ nfsd_file_gc(void)
 				remaining = 0;
 		}
 	}
+	nfsd_file_dispose_list_delayed(&dispose);
 	spin_unlock(&nfsd_gc_lock);
 	trace_nfsd_file_gc_removed(ret, list_lru_count(&nfsd_file_lru));
-	nfsd_file_dispose_list_delayed(&dispose);
 }
 
 static void

@@ -613,9 +623,9 @@ nfsd_file_lru_scan(struct shrinker *s, struct shrink_control *sc)
 
 	ret = list_lru_shrink_walk(&nfsd_file_lru, sc,
 				   nfsd_file_lru_cb, &dispose);
+	nfsd_file_dispose_list_delayed(&dispose);
 	spin_unlock(&nfsd_gc_lock);
 	trace_nfsd_file_shrinker_removed(ret, list_lru_count(&nfsd_file_lru));
-	nfsd_file_dispose_list_delayed(&dispose);
 	return ret;
 }
 

@@ -701,8 +711,10 @@ nfsd_file_close_inode(struct inode *inode)
 {
 	LIST_HEAD(dispose);
 
+	spin_lock(&nfsd_gc_lock);
 	nfsd_file_queue_for_close(inode, &dispose);
 	nfsd_file_dispose_list_delayed(&dispose);
+	spin_unlock(&nfsd_gc_lock);
 }
 
 /**

@@ -925,6 +937,14 @@ nfsd_file_cache_shutdown_net(struct net *net)
 	struct nfsd_net *nn = net_generic(net, nfsd_net_id);
 
 	nfsd_file_cache_purge(net);
+	/*
+	 * Ensure any in-progress shrinker, GC, or fsnotify/lease callback
+	 * (all of which hold nfsd_gc_lock while calling
+	 * nfsd_file_dispose_list_delayed()) has fully completed before
+	 * draining the per-net dispose list.
+	 */
+	spin_lock(&nfsd_gc_lock);
+	spin_unlock(&nfsd_gc_lock);
 	nfsd_file_dispose_list(&nn->fcache_dispose_list);
 }