1 files changed, 99 insertions, 27 deletions

diff --git a/fs/kernfs/mount.c b/fs/kernfs/mount.c
index cfa79715fc1a..3ac52e141766 100644
--- a/fs/kernfs/mount.c
+++ b/fs/kernfs/mount.c
@@ -16,10 +16,14 @@
 #include <linux/namei.h>
 #include <linux/seq_file.h>
 #include <linux/exportfs.h>
+#include <linux/uuid.h>
+#include <linux/statfs.h>
 
 #include "kernfs-internal.h"
 
-struct kmem_cache *kernfs_node_cache, *kernfs_iattrs_cache;
+struct kmem_cache *kernfs_node_cache __ro_after_init;
+struct kmem_cache *kernfs_iattrs_cache __ro_after_init;
+struct kernfs_global_locks *kernfs_locks __ro_after_init;
 
 static int kernfs_sop_show_options(struct seq_file *sf, struct dentry *dentry)
 {
@@ -44,13 +48,35 @@ static int kernfs_sop_show_path(struct seq_file *sf, struct dentry *dentry)
 	return 0;
 }
 
+static int kernfs_statfs(struct dentry *dentry, struct kstatfs *buf)
+{
+	simple_statfs(dentry, buf);
+	buf->f_fsid = uuid_to_fsid(dentry->d_sb->s_uuid.b);
+	return 0;
+}
+
 const struct super_operations kernfs_sops = {
-	.statfs		= simple_statfs,
-	.drop_inode	= generic_delete_inode,
+	.statfs		= kernfs_statfs,
+	.drop_inode	= inode_just_drop,
 	.evict_inode	= kernfs_evict_inode,
 
 	.show_options	= kernfs_sop_show_options,
 	.show_path	= kernfs_sop_show_path,
+
+	/*
+	 * sysfs is built on top of kernfs and sysfs provides the power
+	 * management infrastructure to support suspend/hibernate by
+	 * writing to various files in /sys/power/. As filesystems may
+	 * be automatically frozen during suspend/hibernate implementing
+	 * freeze/thaw support for kernfs generically will cause
+	 * deadlocks as the suspending/hibernation initiating task will
+	 * hold a VFS lock that it will then wait upon to be released.
+	 * If freeze/thaw for kernfs is needed talk to the VFS.
+	 */
+	.freeze_fs	= NULL,
+	.unfreeze_fs	= NULL,
+	.freeze_super	= NULL,
+	.thaw_super	= NULL,
 };
 
 static int kernfs_encode_fh(struct inode *inode, __u32 *fh, int *max_len,
@@ -114,9 +140,6 @@ static struct dentry *__kernfs_fh_to_dentry(struct super_block *sb,
 
 	inode = kernfs_get_inode(sb, kn);
 	kernfs_put(kn);
-	if (!inode)
-		return ERR_PTR(-ESTALE);
-
 	return d_obtain_alias(inode);
 }
 
@@ -137,8 +160,10 @@ static struct dentry *kernfs_fh_to_parent(struct super_block *sb,
 static struct dentry *kernfs_get_parent_dentry(struct dentry *child)
 {
 	struct kernfs_node *kn = kernfs_dentry_node(child);
+	struct kernfs_root *root = kernfs_root(kn);
 
-	return d_obtain_alias(kernfs_get_inode(child->d_sb, kn->parent));
+	guard(rwsem_read)(&root->kernfs_rwsem);
+	return d_obtain_alias(kernfs_get_inode(child->d_sb, kernfs_parent(kn)));
 }
 
 static const struct export_operations kernfs_export_ops = {
@@ -152,7 +177,7 @@ static const struct export_operations kernfs_export_ops = {
  * kernfs_root_from_sb - determine kernfs_root associated with a super_block
  * @sb: the super_block in question
  *
- * Return the kernfs_root associated with @sb.  If @sb is not a kernfs one,
+ * Return: the kernfs_root associated with @sb.  If @sb is not a kernfs one,
  * %NULL is returned.
  */
 struct kernfs_root *kernfs_root_from_sb(struct super_block *sb)
@@ -166,7 +191,7 @@ struct kernfs_root *kernfs_root_from_sb(struct super_block *sb)
  * find the next ancestor in the path down to @child, where @parent was the
  * ancestor whose descendant we want to find.
  *
- * Say the path is /a/b/c/d.  @child is d, @parent is NULL.  We return the root
+ * Say the path is /a/b/c/d.  @child is d, @parent is %NULL.  We return the root
  * node.  If @parent is b, then we return the node for c.
  * Passing in d as @parent is not ok.
  */
@@ -178,10 +203,10 @@ static struct kernfs_node *find_next_ancestor(struct kernfs_node *child,
 		return NULL;
 	}
 
-	while (child->parent != parent) {
-		if (!child->parent)
+	while (kernfs_parent(child) != parent) {
+		child = kernfs_parent(child);
+		if (!child)
 			return NULL;
-		child = child->parent;
 	}
 
 	return child;
@@ -191,22 +216,35 @@ static struct kernfs_node *find_next_ancestor(struct kernfs_node *child,
  * kernfs_node_dentry - get a dentry for the given kernfs_node
  * @kn: kernfs_node for which a dentry is needed
  * @sb: the kernfs super_block
+ *
+ * Return: the dentry pointer
  */
 struct dentry *kernfs_node_dentry(struct kernfs_node *kn,
 				  struct super_block *sb)
 {
 	struct dentry *dentry;
-	struct kernfs_node *knparent = NULL;
+	struct kernfs_node *knparent;
+	struct kernfs_root *root;
 
 	BUG_ON(sb->s_op != &kernfs_sops);
 
 	dentry = dget(sb->s_root);
 
 	/* Check if this is the root kernfs_node */
-	if (!kn->parent)
+	if (!rcu_access_pointer(kn->__parent))
 		return dentry;
 
-	knparent = find_next_ancestor(kn, NULL);
+	root = kernfs_root(kn);
+	/*
+	 * As long as kn is valid, its parent can not vanish. This is cgroup's
+	 * kn so it can't have its parent replaced. Therefore it is safe to use
+	 * the ancestor node outside of the RCU or locked section.
+	 */
+	if (WARN_ON_ONCE(!(root->flags & KERNFS_ROOT_INVARIANT_PARENT)))
+		return ERR_PTR(-EINVAL);
+	scoped_guard(rcu) {
+		knparent = find_next_ancestor(kn, NULL);
+	}
 	if (WARN_ON(!knparent)) {
 		dput(dentry);
 		return ERR_PTR(-EINVAL);
@@ -215,17 +253,26 @@ struct dentry *kernfs_node_dentry(struct kernfs_node *kn,
 	do {
 		struct dentry *dtmp;
 		struct kernfs_node *kntmp;
+		const char *name;
 
 		if (kn == knparent)
 			return dentry;
-		kntmp = find_next_ancestor(kn, knparent);
-		if (WARN_ON(!kntmp)) {
+
+		scoped_guard(rwsem_read, &root->kernfs_rwsem) {
+			kntmp = find_next_ancestor(kn, knparent);
+			if (WARN_ON(!kntmp)) {
+				dput(dentry);
+				return ERR_PTR(-EINVAL);
+			}
+			name = kstrdup(kernfs_rcu_name(kntmp), GFP_KERNEL);
+		}
+		if (!name) {
 			dput(dentry);
-			return ERR_PTR(-EINVAL);
+			return ERR_PTR(-ENOMEM);
 		}
-		dtmp = lookup_positive_unlocked(kntmp->name, dentry,
-					       strlen(kntmp->name));
+		dtmp = lookup_noperm_positive_unlocked(&QSTR(name), dentry);
 		dput(dentry);
+		kfree(name);
 		if (IS_ERR(dtmp))
 			return dtmp;
 		knparent = kntmp;
@@ -251,9 +298,10 @@ static int kernfs_fill_super(struct super_block *sb, struct kernfs_fs_context *k
 	if (info->root->flags & KERNFS_ROOT_SUPPORT_EXPORTOP)
 		sb->s_export_op = &kernfs_export_ops;
 	sb->s_time_gran = 1;
+	sb->s_maxbytes  = MAX_LFS_FILESIZE;
 
 	/* sysfs dentries and inodes don't require IO to create */
-	sb->s_shrink.seeks = 0;
+	sb->s_shrink->seeks = 0;
 
 	/* get root inode, initialize and unlock it */
 	down_read(&kf_root->kernfs_rwsem);
@@ -271,7 +319,7 @@ static int kernfs_fill_super(struct super_block *sb, struct kernfs_fs_context *k
 		return -ENOMEM;
 	}
 	sb->s_root = root;
-	sb->s_d_op = &kernfs_dops;
+	set_default_d_op(sb, &kernfs_dops);
 	return 0;
 }
 
@@ -295,7 +343,7 @@ static int kernfs_set_super(struct super_block *sb, struct fs_context *fc)
  * kernfs_super_ns - determine the namespace tag of a kernfs super_block
  * @sb: super_block of interest
  *
- * Return the namespace tag associated with kernfs super_block @sb.
+ * Return: the namespace tag associated with kernfs super_block @sb.
  */
 const void *kernfs_super_ns(struct super_block *sb)
 {
@@ -312,6 +360,8 @@ const void *kernfs_super_ns(struct super_block *sb)
  * implementation, which should set the specified ->@fs_type and ->@flags, and
  * specify the hierarchy and namespace tag to mount via ->@root and ->@ns,
  * respectively.
+ *
+ * Return: %0 on success, -errno on failure.
  */
 int kernfs_get_tree(struct fs_context *fc)
 {
@@ -346,9 +396,13 @@ int kernfs_get_tree(struct fs_context *fc)
 		}
 		sb->s_flags |= SB_ACTIVE;
 
-		down_write(&root->kernfs_rwsem);
+		uuid_t uuid;
+		uuid_gen(&uuid);
+		super_set_uuid(sb, uuid.b, sizeof(uuid));
+
+		down_write(&root->kernfs_supers_rwsem);
 		list_add(&info->node, &info->root->supers);
-		up_write(&root->kernfs_rwsem);
+		up_write(&root->kernfs_supers_rwsem);
 	}
 
 	fc->root = dget(sb->s_root);
@@ -375,9 +429,9 @@ void kernfs_kill_sb(struct super_block *sb)
 	struct kernfs_super_info *info = kernfs_info(sb);
 	struct kernfs_root *root = info->root;
 
-	down_write(&root->kernfs_rwsem);
+	down_write(&root->kernfs_supers_rwsem);
 	list_del(&info->node);
-	up_write(&root->kernfs_rwsem);
+	up_write(&root->kernfs_supers_rwsem);
 
 	/*
 	 * Remove the superblock from fs_supers/s_instances
@@ -387,6 +441,22 @@ void kernfs_kill_sb(struct super_block *sb)
 	kfree(info);
 }
 
+static void __init kernfs_mutex_init(void)
+{
+	int count;
+
+	for (count = 0; count < NR_KERNFS_LOCKS; count++)
+		mutex_init(&kernfs_locks->open_file_mutex[count]);
+}
+
+static void __init kernfs_lock_init(void)
+{
+	kernfs_locks = kmalloc(sizeof(struct kernfs_global_locks), GFP_KERNEL);
+	WARN_ON(!kernfs_locks);
+
+	kernfs_mutex_init();
+}
+
 void __init kernfs_init(void)
 {
 	kernfs_node_cache = kmem_cache_create("kernfs_node_cache",
@@ -397,4 +467,6 @@ void __init kernfs_init(void)
 	kernfs_iattrs_cache  = kmem_cache_create("kernfs_iattrs_cache",
 					      sizeof(struct kernfs_iattrs),
 					      0, SLAB_PANIC, NULL);
+
+	kernfs_lock_init();
 }