Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net

Cross-merge networking fixes after downstream PR.

Conflicts:

tools/testing/selftests/net/fcnal-test.sh
  d7a2fc1437f7 ("selftests: net: fcnal-test: check if FIPS mode is enabled")
  dd017c72dde6 ("selftests: fcnal: Test SO_DONTROUTE on TCP sockets.")
https://lore.kernel.org/all/5007b52c-dd16-dbf6-8d64-b9701bfa498b@tessares.net/
https://lore.kernel.org/all/20230619105427.4a0df9b3@canb.auug.org.au/

No adjacent changes.

Signed-off-by: Jakub Kicinski <kuba@kernel.org>

7 files changed, 116 insertions, 114 deletions

diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index 6b9d39d65b73..2d0d58fb4e7f 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -2070,7 +2070,6 @@ static int collapse_file(struct mm_struct *mm, unsigned long addr,
 					TTU_IGNORE_MLOCK | TTU_BATCH_FLUSH);
 
 		xas_lock_irq(&xas);
-		xas_set(&xas, index);
 
 		VM_BUG_ON_PAGE(page != xas_load(&xas), page);
 
diff --git a/mm/memfd.c b/mm/memfd.c
index 69b90c31d38c..e763e76f1106 100644
--- a/mm/memfd.c
+++ b/mm/memfd.c
@@ -371,12 +371,15 @@ SYSCALL_DEFINE2(memfd_create,
 
 		inode->i_mode &= ~0111;
 		file_seals = memfd_file_seals_ptr(file);
-		*file_seals &= ~F_SEAL_SEAL;
-		*file_seals |= F_SEAL_EXEC;
+		if (file_seals) {
+			*file_seals &= ~F_SEAL_SEAL;
+			*file_seals |= F_SEAL_EXEC;
+		}
 	} else if (flags & MFD_ALLOW_SEALING) {
 		/* MFD_EXEC and MFD_ALLOW_SEALING are set */
 		file_seals = memfd_file_seals_ptr(file);
-		*file_seals &= ~F_SEAL_SEAL;
+		if (file_seals)
+			*file_seals &= ~F_SEAL_SEAL;
 	}
 
 	fd_install(fd, file);
diff --git a/mm/mmap.c b/mm/mmap.c
index 13678edaa22c..d600404580b2 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -2318,21 +2318,6 @@ int split_vma(struct vma_iterator *vmi, struct vm_area_struct *vma,
 	return __split_vma(vmi, vma, addr, new_below);
 }
 
-static inline int munmap_sidetree(struct vm_area_struct *vma,
-				   struct ma_state *mas_detach)
-{
-	vma_start_write(vma);
-	mas_set_range(mas_detach, vma->vm_start, vma->vm_end - 1);
-	if (mas_store_gfp(mas_detach, vma, GFP_KERNEL))
-		return -ENOMEM;
-
-	vma_mark_detached(vma, true);
-	if (vma->vm_flags & VM_LOCKED)
-		vma->vm_mm->locked_vm -= vma_pages(vma);
-
-	return 0;
-}
-
 /*
  * do_vmi_align_munmap() - munmap the aligned region from @start to @end.
  * @vmi: The vma iterator
@@ -2354,6 +2339,7 @@ do_vmi_align_munmap(struct vma_iterator *vmi, struct vm_area_struct *vma,
 	struct maple_tree mt_detach;
 	int count = 0;
 	int error = -ENOMEM;
+	unsigned long locked_vm = 0;
 	MA_STATE(mas_detach, &mt_detach, 0, 0);
 	mt_init_flags(&mt_detach, vmi->mas.tree->ma_flags & MT_FLAGS_LOCK_MASK);
 	mt_set_external_lock(&mt_detach, &mm->mmap_lock);
@@ -2399,9 +2385,13 @@ do_vmi_align_munmap(struct vma_iterator *vmi, struct vm_area_struct *vma,
 			if (error)
 				goto end_split_failed;
 		}
-		error = munmap_sidetree(next, &mas_detach);
-		if (error)
-			goto munmap_sidetree_failed;
+		vma_start_write(next);
+		mas_set_range(&mas_detach, next->vm_start, next->vm_end - 1);
+		if (mas_store_gfp(&mas_detach, next, GFP_KERNEL))
+			goto munmap_gather_failed;
+		vma_mark_detached(next, true);
+		if (next->vm_flags & VM_LOCKED)
+			locked_vm += vma_pages(next);
 
 		count++;
 #ifdef CONFIG_DEBUG_VM_MAPLE_TREE
@@ -2447,10 +2437,12 @@ do_vmi_align_munmap(struct vma_iterator *vmi, struct vm_area_struct *vma,
 	}
 #endif
 	/* Point of no return */
+	error = -ENOMEM;
 	vma_iter_set(vmi, start);
 	if (vma_iter_clear_gfp(vmi, start, end, GFP_KERNEL))
-		return -ENOMEM;
+		goto clear_tree_failed;
 
+	mm->locked_vm -= locked_vm;
 	mm->map_count -= count;
 	/*
 	 * Do not downgrade mmap_lock if we are next to VM_GROWSDOWN or
@@ -2480,9 +2472,14 @@ do_vmi_align_munmap(struct vma_iterator *vmi, struct vm_area_struct *vma,
 	validate_mm(mm);
 	return downgrade ? 1 : 0;
 
+clear_tree_failed:
 userfaultfd_error:
-munmap_sidetree_failed:
+munmap_gather_failed:
 end_split_failed:
+	mas_set(&mas_detach, 0);
+	mas_for_each(&mas_detach, next, end)
+		vma_mark_detached(next, false);
+
 	__mt_destroy(&mt_detach);
 start_split_failed:
 map_count_exceeded:
diff --git a/mm/mprotect.c b/mm/mprotect.c
index 92d3d3ca390a..c59e7561698c 100644
--- a/mm/mprotect.c
+++ b/mm/mprotect.c
@@ -867,7 +867,7 @@ static int do_mprotect_pkey(unsigned long start, size_t len,
 	}
 	tlb_finish_mmu(&tlb);
 
-	if (!error && vma_iter_end(&vmi) < end)
+	if (!error && tmp < end)
 		error = -ENOMEM;
 
 out:
diff --git a/mm/shrinker_debug.c b/mm/shrinker_debug.c
index fe10436d9911..3ab53fad8876 100644
--- a/mm/shrinker_debug.c
+++ b/mm/shrinker_debug.c
@@ -5,12 +5,10 @@
 #include <linux/seq_file.h>
 #include <linux/shrinker.h>
 #include <linux/memcontrol.h>
-#include <linux/srcu.h>
 
 /* defined in vmscan.c */
-extern struct mutex shrinker_mutex;
+extern struct rw_semaphore shrinker_rwsem;
 extern struct list_head shrinker_list;
-extern struct srcu_struct shrinker_srcu;
 
 static DEFINE_IDA(shrinker_debugfs_ida);
 static struct dentry *shrinker_debugfs_root;
@@ -51,13 +49,18 @@ static int shrinker_debugfs_count_show(struct seq_file *m, void *v)
 	struct mem_cgroup *memcg;
 	unsigned long total;
 	bool memcg_aware;
-	int ret = 0, nid, srcu_idx;
+	int ret, nid;
 
 	count_per_node = kcalloc(nr_node_ids, sizeof(unsigned long), GFP_KERNEL);
 	if (!count_per_node)
 		return -ENOMEM;
 
-	srcu_idx = srcu_read_lock(&shrinker_srcu);
+	ret = down_read_killable(&shrinker_rwsem);
+	if (ret) {
+		kfree(count_per_node);
+		return ret;
+	}
+	rcu_read_lock();
 
 	memcg_aware = shrinker->flags & SHRINKER_MEMCG_AWARE;
 
@@ -88,7 +91,8 @@ static int shrinker_debugfs_count_show(struct seq_file *m, void *v)
 		}
 	} while ((memcg = mem_cgroup_iter(NULL, memcg, NULL)) != NULL);
 
-	srcu_read_unlock(&shrinker_srcu, srcu_idx);
+	rcu_read_unlock();
+	up_read(&shrinker_rwsem);
 
 	kfree(count_per_node);
 	return ret;
@@ -111,8 +115,9 @@ static ssize_t shrinker_debugfs_scan_write(struct file *file,
 		.gfp_mask = GFP_KERNEL,
 	};
 	struct mem_cgroup *memcg = NULL;
-	int nid, srcu_idx;
+	int nid;
 	char kbuf[72];
+	ssize_t ret;
 
 	read_len = size < (sizeof(kbuf) - 1) ? size : (sizeof(kbuf) - 1);
 	if (copy_from_user(kbuf, buf, read_len))
@@ -141,7 +146,11 @@ static ssize_t shrinker_debugfs_scan_write(struct file *file,
 		return -EINVAL;
 	}
 
-	srcu_idx = srcu_read_lock(&shrinker_srcu);
+	ret = down_read_killable(&shrinker_rwsem);
+	if (ret) {
+		mem_cgroup_put(memcg);
+		return ret;
+	}
 
 	sc.nid = nid;
 	sc.memcg = memcg;
@@ -150,7 +159,7 @@ static ssize_t shrinker_debugfs_scan_write(struct file *file,
 
 	shrinker->scan_objects(shrinker, &sc);
 
-	srcu_read_unlock(&shrinker_srcu, srcu_idx);
+	up_read(&shrinker_rwsem);
 	mem_cgroup_put(memcg);
 
 	return size;
@@ -168,7 +177,7 @@ int shrinker_debugfs_add(struct shrinker *shrinker)
 	char buf[128];
 	int id;
 
-	lockdep_assert_held(&shrinker_mutex);
+	lockdep_assert_held(&shrinker_rwsem);
 
 	/* debugfs isn't initialized yet, add debugfs entries later. */
 	if (!shrinker_debugfs_root)
@@ -211,7 +220,7 @@ int shrinker_debugfs_rename(struct shrinker *shrinker, const char *fmt, ...)
 	if (!new)
 		return -ENOMEM;
 
-	mutex_lock(&shrinker_mutex);
+	down_write(&shrinker_rwsem);
 
 	old = shrinker->name;
 	shrinker->name = new;
@@ -229,7 +238,7 @@ int shrinker_debugfs_rename(struct shrinker *shrinker, const char *fmt, ...)
 			shrinker->debugfs_entry = entry;
 	}
 
-	mutex_unlock(&shrinker_mutex);
+	up_write(&shrinker_rwsem);
 
 	kfree_const(old);
 
@@ -242,7 +251,7 @@ struct dentry *shrinker_debugfs_detach(struct shrinker *shrinker,
 {
 	struct dentry *entry = shrinker->debugfs_entry;
 
-	lockdep_assert_held(&shrinker_mutex);
+	lockdep_assert_held(&shrinker_rwsem);
 
 	kfree_const(shrinker->name);
 	shrinker->name = NULL;
@@ -271,14 +280,14 @@ static int __init shrinker_debugfs_init(void)
 	shrinker_debugfs_root = dentry;
 
 	/* Create debugfs entries for shrinkers registered at boot */
-	mutex_lock(&shrinker_mutex);
+	down_write(&shrinker_rwsem);
 	list_for_each_entry(shrinker, &shrinker_list, list)
 		if (!shrinker->debugfs_entry) {
 			ret = shrinker_debugfs_add(shrinker);
 			if (ret)
 				break;
 		}
-	mutex_unlock(&shrinker_mutex);
+	up_write(&shrinker_rwsem);
 
 	return ret;
 }
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 9683573f1225..1d13d71687d7 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -3098,11 +3098,20 @@ static void *__vmalloc_area_node(struct vm_struct *area, gfp_t gfp_mask,
 	 * allocation request, free them via vfree() if any.
 	 */
 	if (area->nr_pages != nr_small_pages) {
-		/* vm_area_alloc_pages() can also fail due to a fatal signal */
-		if (!fatal_signal_pending(current))
+		/*
+		 * vm_area_alloc_pages() can fail due to insufficient memory but
+		 * also:-
+		 *
+		 * - a pending fatal signal
+		 * - insufficient huge page-order pages
+		 *
+		 * Since we always retry allocations at order-0 in the huge page
+		 * case a warning for either is spurious.
+		 */
+		if (!fatal_signal_pending(current) && page_order == 0)
 			warn_alloc(gfp_mask, NULL,
-				"vmalloc error: size %lu, page order %u, failed to allocate pages",
-				area->nr_pages * PAGE_SIZE, page_order);
+				"vmalloc error: size %lu, failed to allocate pages",
+				area->nr_pages * PAGE_SIZE);
 		goto fail;
 	}
 
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 6d0cd2840cf0..5bf98d0a22c9 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -35,7 +35,7 @@
 #include <linux/cpuset.h>
 #include <linux/compaction.h>
 #include <linux/notifier.h>
-#include <linux/mutex.h>
+#include <linux/rwsem.h>
 #include <linux/delay.h>
 #include <linux/kthread.h>
 #include <linux/freezer.h>
@@ -57,7 +57,6 @@
 #include <linux/khugepaged.h>
 #include <linux/rculist_nulls.h>
 #include <linux/random.h>
-#include <linux/srcu.h>
 
 #include <asm/tlbflush.h>
 #include <asm/div64.h>
@@ -190,9 +189,7 @@ struct scan_control {
 int vm_swappiness = 60;
 
 LIST_HEAD(shrinker_list);
-DEFINE_MUTEX(shrinker_mutex);
-DEFINE_SRCU(shrinker_srcu);
-static atomic_t shrinker_srcu_generation = ATOMIC_INIT(0);
+DECLARE_RWSEM(shrinker_rwsem);
 
 #ifdef CONFIG_MEMCG
 static int shrinker_nr_max;
@@ -211,21 +208,8 @@ static inline int shrinker_defer_size(int nr_items)
 static struct shrinker_info *shrinker_info_protected(struct mem_cgroup *memcg,
 						     int nid)
 {
-	return srcu_dereference_check(memcg->nodeinfo[nid]->shrinker_info,
-				      &shrinker_srcu,
-				      lockdep_is_held(&shrinker_mutex));
-}
-
-static struct shrinker_info *shrinker_info_srcu(struct mem_cgroup *memcg,
-						     int nid)
-{
-	return srcu_dereference(memcg->nodeinfo[nid]->shrinker_info,
-				&shrinker_srcu);
-}
-
-static void free_shrinker_info_rcu(struct rcu_head *head)
-{
-	kvfree(container_of(head, struct shrinker_info, rcu));
+	return rcu_dereference_protected(memcg->nodeinfo[nid]->shrinker_info,
+					 lockdep_is_held(&shrinker_rwsem));
 }
 
 static int expand_one_shrinker_info(struct mem_cgroup *memcg,
@@ -266,7 +250,7 @@ static int expand_one_shrinker_info(struct mem_cgroup *memcg,
 		       defer_size - old_defer_size);
 
 		rcu_assign_pointer(pn->shrinker_info, new);
-		call_srcu(&shrinker_srcu, &old->rcu, free_shrinker_info_rcu);
+		kvfree_rcu(old, rcu);
 	}
 
 	return 0;
@@ -292,7 +276,7 @@ int alloc_shrinker_info(struct mem_cgroup *memcg)
 	int nid, size, ret = 0;
 	int map_size, defer_size = 0;
 
-	mutex_lock(&shrinker_mutex);
+	down_write(&shrinker_rwsem);
 	map_size = shrinker_map_size(shrinker_nr_max);
 	defer_size = shrinker_defer_size(shrinker_nr_max);
 	size = map_size + defer_size;
@@ -308,7 +292,7 @@ int alloc_shrinker_info(struct mem_cgroup *memcg)
 		info->map_nr_max = shrinker_nr_max;
 		rcu_assign_pointer(memcg->nodeinfo[nid]->shrinker_info, info);
 	}
-	mutex_unlock(&shrinker_mutex);
+	up_write(&shrinker_rwsem);
 
 	return ret;
 }
@@ -324,7 +308,7 @@ static int expand_shrinker_info(int new_id)
 	if (!root_mem_cgroup)
 		goto out;
 
-	lockdep_assert_held(&shrinker_mutex);
+	lockdep_assert_held(&shrinker_rwsem);
 
 	map_size = shrinker_map_size(new_nr_max);
 	defer_size = shrinker_defer_size(new_nr_max);
@@ -352,16 +336,15 @@ void set_shrinker_bit(struct mem_cgroup *memcg, int nid, int shrinker_id)
 {
 	if (shrinker_id >= 0 && memcg && !mem_cgroup_is_root(memcg)) {
 		struct shrinker_info *info;
-		int srcu_idx;
 
-		srcu_idx = srcu_read_lock(&shrinker_srcu);
-		info = shrinker_info_srcu(memcg, nid);
+		rcu_read_lock();
+		info = rcu_dereference(memcg->nodeinfo[nid]->shrinker_info);
 		if (!WARN_ON_ONCE(shrinker_id >= info->map_nr_max)) {
 			/* Pairs with smp mb in shrink_slab() */
 			smp_mb__before_atomic();
 			set_bit(shrinker_id, info->map);
 		}
-		srcu_read_unlock(&shrinker_srcu, srcu_idx);
+		rcu_read_unlock();
 	}
 }
 
@@ -374,7 +357,8 @@ static int prealloc_memcg_shrinker(struct shrinker *shrinker)
 	if (mem_cgroup_disabled())
 		return -ENOSYS;
 
-	mutex_lock(&shrinker_mutex);
+	down_write(&shrinker_rwsem);
+	/* This may call shrinker, so it must use down_read_trylock() */
 	id = idr_alloc(&shrinker_idr, shrinker, 0, 0, GFP_KERNEL);
 	if (id < 0)
 		goto unlock;
@@ -388,7 +372,7 @@ static int prealloc_memcg_shrinker(struct shrinker *shrinker)
 	shrinker->id = id;
 	ret = 0;
 unlock:
-	mutex_unlock(&shrinker_mutex);
+	up_write(&shrinker_rwsem);
 	return ret;
 }
 
@@ -398,7 +382,7 @@ static void unregister_memcg_shrinker(struct shrinker *shrinker)
 
 	BUG_ON(id < 0);
 
-	lockdep_assert_held(&shrinker_mutex);
+	lockdep_assert_held(&shrinker_rwsem);
 
 	idr_remove(&shrinker_idr, id);
 }
@@ -408,7 +392,7 @@ static long xchg_nr_deferred_memcg(int nid, struct shrinker *shrinker,
 {
 	struct shrinker_info *info;
 
-	info = shrinker_info_srcu(memcg, nid);
+	info = shrinker_info_protected(memcg, nid);
 	return atomic_long_xchg(&info->nr_deferred[shrinker->id], 0);
 }
 
@@ -417,7 +401,7 @@ static long add_nr_deferred_memcg(long nr, int nid, struct shrinker *shrinker,
 {
 	struct shrinker_info *info;
 
-	info = shrinker_info_srcu(memcg, nid);
+	info = shrinker_info_protected(memcg, nid);
 	return atomic_long_add_return(nr, &info->nr_deferred[shrinker->id]);
 }
 
@@ -433,7 +417,7 @@ void reparent_shrinker_deferred(struct mem_cgroup *memcg)
 		parent = root_mem_cgroup;
 
 	/* Prevent from concurrent shrinker_info expand */
-	mutex_lock(&shrinker_mutex);
+	down_read(&shrinker_rwsem);
 	for_each_node(nid) {
 		child_info = shrinker_info_protected(memcg, nid);
 		parent_info = shrinker_info_protected(parent, nid);
@@ -442,7 +426,7 @@ void reparent_shrinker_deferred(struct mem_cgroup *memcg)
 			atomic_long_add(nr, &parent_info->nr_deferred[i]);
 		}
 	}
-	mutex_unlock(&shrinker_mutex);
+	up_read(&shrinker_rwsem);
 }
 
 static bool cgroup_reclaim(struct scan_control *sc)
@@ -743,9 +727,9 @@ void free_prealloced_shrinker(struct shrinker *shrinker)
 	shrinker->name = NULL;
 #endif
 	if (shrinker->flags & SHRINKER_MEMCG_AWARE) {
-		mutex_lock(&shrinker_mutex);
+		down_write(&shrinker_rwsem);
 		unregister_memcg_shrinker(shrinker);
-		mutex_unlock(&shrinker_mutex);
+		up_write(&shrinker_rwsem);
 		return;
 	}
 
@@ -755,11 +739,11 @@ void free_prealloced_shrinker(struct shrinker *shrinker)
 
 void register_shrinker_prepared(struct shrinker *shrinker)
 {
-	mutex_lock(&shrinker_mutex);
-	list_add_tail_rcu(&shrinker->list, &shrinker_list);
+	down_write(&shrinker_rwsem);
+	list_add_tail(&shrinker->list, &shrinker_list);
 	shrinker->flags |= SHRINKER_REGISTERED;
 	shrinker_debugfs_add(shrinker);
-	mutex_unlock(&shrinker_mutex);
+	up_write(&shrinker_rwsem);
 }
 
 static int __register_shrinker(struct shrinker *shrinker)
@@ -810,16 +794,13 @@ void unregister_shrinker(struct shrinker *shrinker)
 	if (!(shrinker->flags & SHRINKER_REGISTERED))
 		return;
 
-	mutex_lock(&shrinker_mutex);
-	list_del_rcu(&shrinker->list);
+	down_write(&shrinker_rwsem);
+	list_del(&shrinker->list);
 	shrinker->flags &= ~SHRINKER_REGISTERED;
 	if (shrinker->flags & SHRINKER_MEMCG_AWARE)
 		unregister_memcg_shrinker(shrinker);
 	debugfs_entry = shrinker_debugfs_detach(shrinker, &debugfs_id);
-	mutex_unlock(&shrinker_mutex);
-
-	atomic_inc(&shrinker_srcu_generation);
-	synchronize_srcu(&shrinker_srcu);
+	up_write(&shrinker_rwsem);
 
 	shrinker_debugfs_remove(debugfs_entry, debugfs_id);
 
@@ -831,13 +812,15 @@ EXPORT_SYMBOL(unregister_shrinker);
 /**
  * synchronize_shrinkers - Wait for all running shrinkers to complete.
  *
- * This is useful to guarantee that all shrinker invocations have seen an
- * update, before freeing memory.
+ * This is equivalent to calling unregister_shrink() and register_shrinker(),
+ * but atomically and with less overhead. This is useful to guarantee that all
+ * shrinker invocations have seen an update, before freeing memory, similar to
+ * rcu.
  */
 void synchronize_shrinkers(void)
 {
-	atomic_inc(&shrinker_srcu_generation);
-	synchronize_srcu(&shrinker_srcu);
+	down_write(&shrinker_rwsem);
+	up_write(&shrinker_rwsem);
 }
 EXPORT_SYMBOL(synchronize_shrinkers);
 
@@ -946,20 +929,19 @@ static unsigned long shrink_slab_memcg(gfp_t gfp_mask, int nid,
 {
 	struct shrinker_info *info;
 	unsigned long ret, freed = 0;
-	int srcu_idx, generation;
-	int i = 0;
+	int i;
 
 	if (!mem_cgroup_online(memcg))
 		return 0;
 
-again:
-	srcu_idx = srcu_read_lock(&shrinker_srcu);
-	info = shrinker_info_srcu(memcg, nid);
+	if (!down_read_trylock(&shrinker_rwsem))
+		return 0;
+
+	info = shrinker_info_protected(memcg, nid);
 	if (unlikely(!info))
 		goto unlock;
 
-	generation = atomic_read(&shrinker_srcu_generation);
-	for_each_set_bit_from(i, info->map, info->map_nr_max) {
+	for_each_set_bit(i, info->map, info->map_nr_max) {
 		struct shrink_control sc = {
 			.gfp_mask = gfp_mask,
 			.nid = nid,
@@ -1005,14 +987,14 @@ again:
 				set_shrinker_bit(memcg, nid, i);
 		}
 		freed += ret;
-		if (atomic_read(&shrinker_srcu_generation) != generation) {
-			srcu_read_unlock(&shrinker_srcu, srcu_idx);
-			i++;
-			goto again;
+
+		if (rwsem_is_contended(&shrinker_rwsem)) {
+			freed = freed ? : 1;
+			break;
 		}
 	}
 unlock:
-	srcu_read_unlock(&shrinker_srcu, srcu_idx);
+	up_read(&shrinker_rwsem);
 	return freed;
 }
 #else /* CONFIG_MEMCG */
@@ -1049,7 +1031,6 @@ static unsigned long shrink_slab(gfp_t gfp_mask, int nid,
 {
 	unsigned long ret, freed = 0;
 	struct shrinker *shrinker;
-	int srcu_idx, generation;
 
 	/*
 	 * The root memcg might be allocated even though memcg is disabled
@@ -1061,11 +1042,10 @@ static unsigned long shrink_slab(gfp_t gfp_mask, int nid,
 	if (!mem_cgroup_disabled() && !mem_cgroup_is_root(memcg))
 		return shrink_slab_memcg(gfp_mask, nid, memcg, priority);
 
-	srcu_idx = srcu_read_lock(&shrinker_srcu);
+	if (!down_read_trylock(&shrinker_rwsem))
+		goto out;
 
-	generation = atomic_read(&shrinker_srcu_generation);
-	list_for_each_entry_srcu(shrinker, &shrinker_list, list,
-				 srcu_read_lock_held(&shrinker_srcu)) {
+	list_for_each_entry(shrinker, &shrinker_list, list) {
 		struct shrink_control sc = {
 			.gfp_mask = gfp_mask,
 			.nid = nid,
@@ -1076,14 +1056,19 @@ static unsigned long shrink_slab(gfp_t gfp_mask, int nid,
 		if (ret == SHRINK_EMPTY)
 			ret = 0;
 		freed += ret;
-
-		if (atomic_read(&shrinker_srcu_generation) != generation) {
+		/*
+		 * Bail out if someone want to register a new shrinker to
+		 * prevent the registration from being stalled for long periods
+		 * by parallel ongoing shrinking.
+		 */
+		if (rwsem_is_contended(&shrinker_rwsem)) {
 			freed = freed ? : 1;
 			break;
 		}
 	}
 
-	srcu_read_unlock(&shrinker_srcu, srcu_idx);
+	up_read(&shrinker_rwsem);
+out:
 	cond_resched();
 	return freed;
 }