kernfs: remove kernfs_addrm_cxt

kernfs_addrm_cxt and the accompanying kernfs_addrm_start/finish() were
added because there were operations which should be performed outside
kernfs_mutex after adding and removing kernfs_nodes.  The necessary
operations were recorded in kernfs_addrm_cxt and performed by
kernfs_addrm_finish(); however, after the recent changes which
relocated deactivation and unmapping so that they're performed
directly during removal, the only operation kernfs_addrm_finish()
performs is kernfs_put(), which can be moved inside the removal path
too.

This patch moves the kernfs_put() of the base ref to __kernfs_remove()
and remove kernfs_addrm_cxt and kernfs_addrm_start/finish().

* kernfs_add_one() is updated to grab and release kernfs_mutex itself.
  sysfs_addrm_start/finish() invocations around it are removed from
  all users.

* __kernfs_remove() puts an unlinked node directly instead of chaining
  it to kernfs_addrm_cxt.  Its callers are updated to grab and release
  kernfs_mutex instead of calling kernfs_addrm_start/finish() around
  it.

v2: Rebased on top of "kernfs: associate a new kernfs_node with its
    parent on creation" which dropped @parent from kernfs_add_one().

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

4 files changed, 28 insertions, 104 deletions

diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c
index 9603c06550a0..948551d222b4 100644
--- a/fs/kernfs/dir.c
+++ b/fs/kernfs/dir.c
@@ -396,69 +396,44 @@ struct kernfs_node *kernfs_new_node(struct kernfs_node *parent,
 }
 
 /**
- *      kernfs_addrm_start - prepare for kernfs_node add/remove
- *      @acxt: pointer to kernfs_addrm_cxt to be used
- *
- *      This function is called when the caller is about to add or remove
- *      kernfs_node.  This function acquires kernfs_mutex.  @acxt is used
- *      to keep and pass context to other addrm functions.
- *
- *      LOCKING:
- *      Kernel thread context (may sleep).  kernfs_mutex is locked on
- *      return.
- */
-void kernfs_addrm_start(struct kernfs_addrm_cxt *acxt)
-        __acquires(kernfs_mutex)
-{
-        memset(acxt, 0, sizeof(*acxt));
-
-        mutex_lock(&kernfs_mutex);
-}
-
-/**
  *      kernfs_add_one - add kernfs_node to parent without warning
- *      @acxt: addrm context to use
  *      @kn: kernfs_node to be added
  *
  *      The caller must already have initialized @kn->parent.  This
  *      function increments nlink of the parent's inode if @kn is a
  *      directory and link into the children list of the parent.
  *
- *      This function should be called between calls to
- *      kernfs_addrm_start() and kernfs_addrm_finish() and should be passed
- *      the same @acxt as passed to kernfs_addrm_start().
- *
- *      LOCKING:
- *      Determined by kernfs_addrm_start().
- *
  *      RETURNS:
  *      0 on success, -EEXIST if entry with the given name already
  *      exists.
  */
-int kernfs_add_one(struct kernfs_addrm_cxt *acxt, struct kernfs_node *kn)
+int kernfs_add_one(struct kernfs_node *kn)
 {
         struct kernfs_node *parent = kn->parent;
-        bool has_ns = kernfs_ns_enabled(parent);
         struct kernfs_iattrs *ps_iattr;
+        bool has_ns;
         int ret;
 
-        if (has_ns != (bool)kn->ns) {
-                WARN(1, KERN_WARNING "kernfs: ns %s in '%s' for '%s'\n",
-                     has_ns ? "required" : "invalid", parent->name, kn->name);
-                return -EINVAL;
-        }
+        mutex_lock(&kernfs_mutex);
+
+        ret = -EINVAL;
+        has_ns = kernfs_ns_enabled(parent);
+        if (WARN(has_ns != (bool)kn->ns, KERN_WARNING "kernfs: ns %s in '%s' for '%s'\n",
+                 has_ns ? "required" : "invalid", parent->name, kn->name))
+                goto out_unlock;
 
         if (kernfs_type(parent) != KERNFS_DIR)
-                return -EINVAL;
+                goto out_unlock;
 
+        ret = -ENOENT;
         if (parent->flags & KERNFS_REMOVED)
-                return -ENOENT;
+                goto out_unlock;
 
         kn->hash = kernfs_name_hash(kn->name, kn->ns);
 
         ret = kernfs_link_sibling(kn);
         if (ret)
-                return ret;
+                goto out_unlock;
 
         /* Update timestamps on the parent */
         ps_iattr = parent->iattr;
@@ -469,35 +444,10 @@ int kernfs_add_one(struct kernfs_addrm_cxt *acxt, struct kernfs_node *kn)
 
         /* Mark the entry added into directory tree */
         kn->flags &= ~KERNFS_REMOVED;
-
-        return 0;
-}
-
-/**
- *      kernfs_addrm_finish - finish up kernfs_node add/remove
- *      @acxt: addrm context to finish up
- *
- *      Finish up kernfs_node add/remove.  Resources acquired by
- *      kernfs_addrm_start() are released and removed kernfs_nodes are
- *      cleaned up.
- *
- *      LOCKING:
- *      kernfs_mutex is released.
- */
-void kernfs_addrm_finish(struct kernfs_addrm_cxt *acxt)
-        __releases(kernfs_mutex)
-{
-        /* release resources acquired by kernfs_addrm_start() */
+        ret = 0;
+out_unlock:
         mutex_unlock(&kernfs_mutex);
-
-        /* kill removed kernfs_nodes */
-        while (acxt->removed) {
-                struct kernfs_node *kn = acxt->removed;
-
-                acxt->removed = kn->u.removed_list;
-
-                kernfs_put(kn);
-        }
+        return ret;
 }
 
 /**
@@ -630,7 +580,6 @@ struct kernfs_node *kernfs_create_dir_ns(struct kernfs_node *parent,
                                          const char *name, umode_t mode,
                                          void *priv, const void *ns)
 {
-        struct kernfs_addrm_cxt acxt;
         struct kernfs_node *kn;
         int rc;
 
@@ -644,10 +593,7 @@ struct kernfs_node *kernfs_create_dir_ns(struct kernfs_node *parent,
         kn->priv = priv;
 
         /* link in */
-        kernfs_addrm_start(&acxt);
-        rc = kernfs_add_one(&acxt, kn);
-        kernfs_addrm_finish(&acxt);
-
+        rc = kernfs_add_one(kn);
         if (!rc)
                 return kn;
 
@@ -800,8 +746,7 @@ static struct kernfs_node *kernfs_next_descendant_post(struct kernfs_node *pos,
         return pos->parent;
 }
 
-static void __kernfs_remove(struct kernfs_addrm_cxt *acxt,
-                            struct kernfs_node *kn)
+static void __kernfs_remove(struct kernfs_node *kn)
 {
         struct kernfs_node *pos;
 
@@ -845,8 +790,7 @@ static void __kernfs_remove(struct kernfs_addrm_cxt *acxt,
                                 ps_iattr->ia_iattr.ia_mtime = CURRENT_TIME;
                         }
 
-                        pos->u.removed_list = acxt->removed;
-                        acxt->removed = pos;
+                        kernfs_put(pos);
                 }
 
                 kernfs_put(pos);
@@ -861,11 +805,9 @@ static void __kernfs_remove(struct kernfs_addrm_cxt *acxt,
  */
 void kernfs_remove(struct kernfs_node *kn)
 {
-        struct kernfs_addrm_cxt acxt;
-
-        kernfs_addrm_start(&acxt);
-        __kernfs_remove(&acxt, kn);
-        kernfs_addrm_finish(&acxt);
+        mutex_lock(&kernfs_mutex);
+        __kernfs_remove(kn);
+        mutex_unlock(&kernfs_mutex);
 }
 
 /**
@@ -880,7 +822,6 @@ void kernfs_remove(struct kernfs_node *kn)
 int kernfs_remove_by_name_ns(struct kernfs_node *parent, const char *name,
                              const void *ns)
 {
-        struct kernfs_addrm_cxt acxt;
         struct kernfs_node *kn;
 
         if (!parent) {
@@ -889,13 +830,13 @@ int kernfs_remove_by_name_ns(struct kernfs_node *parent, const char *name,
                 return -ENOENT;
         }
 
-        kernfs_addrm_start(&acxt);
+        mutex_lock(&kernfs_mutex);
 
         kn = kernfs_find_ns(parent, name, ns);
         if (kn)
-                __kernfs_remove(&acxt, kn);
+                __kernfs_remove(kn);
 
-        kernfs_addrm_finish(&acxt);
+        mutex_unlock(&kernfs_mutex);
 
         if (kn)
                 return 0;
diff --git a/fs/kernfs/file.c b/fs/kernfs/file.c
index dbf397bfdff2..10a8c91c49d6 100644
--- a/fs/kernfs/file.c
+++ b/fs/kernfs/file.c
@@ -820,7 +820,6 @@ struct kernfs_node *__kernfs_create_file(struct kernfs_node *parent,
                                          bool name_is_static,
                                          struct lock_class_key *key)
 {
-        struct kernfs_addrm_cxt acxt;
         struct kernfs_node *kn;
         unsigned flags;
         int rc;
@@ -855,10 +854,7 @@ struct kernfs_node *__kernfs_create_file(struct kernfs_node *parent,
         if (ops->mmap)
                 kn->flags |= KERNFS_HAS_MMAP;
 
-        kernfs_addrm_start(&acxt);
-        rc = kernfs_add_one(&acxt, kn);
-        kernfs_addrm_finish(&acxt);
-
+        rc = kernfs_add_one(kn);
         if (rc) {
                 kernfs_put(kn);
                 return ERR_PTR(rc);
diff --git a/fs/kernfs/kernfs-internal.h b/fs/kernfs/kernfs-internal.h
index eb536b76374a..46b58de794d6 100644
--- a/fs/kernfs/kernfs-internal.h
+++ b/fs/kernfs/kernfs-internal.h
@@ -45,13 +45,6 @@ static inline struct kernfs_root *kernfs_root(struct kernfs_node *kn)
 }
 
 /*
- * Context structure to be used while adding/removing nodes.
- */
-struct kernfs_addrm_cxt {
-        struct kernfs_node      *removed;
-};
-
-/*
  * mount.c
  */
 struct kernfs_super_info {
@@ -100,9 +93,7 @@ extern const struct inode_operations kernfs_dir_iops;
 
 struct kernfs_node *kernfs_get_active(struct kernfs_node *kn);
 void kernfs_put_active(struct kernfs_node *kn);
-void kernfs_addrm_start(struct kernfs_addrm_cxt *acxt);
-int kernfs_add_one(struct kernfs_addrm_cxt *acxt, struct kernfs_node *kn);
-void kernfs_addrm_finish(struct kernfs_addrm_cxt *acxt);
+int kernfs_add_one(struct kernfs_node *kn);
 struct kernfs_node *kernfs_new_node(struct kernfs_node *parent,
                                     const char *name, umode_t mode,
                                     unsigned flags);
diff --git a/fs/kernfs/symlink.c b/fs/kernfs/symlink.c
index 4d457055acb9..8a198898e39a 100644
--- a/fs/kernfs/symlink.c
+++ b/fs/kernfs/symlink.c
@@ -27,7 +27,6 @@ struct kernfs_node *kernfs_create_link(struct kernfs_node *parent,
                                        struct kernfs_node *target)
 {
         struct kernfs_node *kn;
-        struct kernfs_addrm_cxt acxt;
         int error;
 
         kn = kernfs_new_node(parent, name, S_IFLNK|S_IRWXUGO, KERNFS_LINK);
@@ -39,10 +38,7 @@ struct kernfs_node *kernfs_create_link(struct kernfs_node *parent,
         kn->symlink.target_kn = target;
         kernfs_get(target);     /* ref owned by symlink */
 
-        kernfs_addrm_start(&acxt);
-        error = kernfs_add_one(&acxt, kn);
-        kernfs_addrm_finish(&acxt);
-
+        error = kernfs_add_one(kn);
         if (!error)
                 return kn;