[PATCH 07/14] kernfs: remove kernfs_addrm_cxt

Tejun Heo
2014-01-10T13:58:03Z

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 the parent's active
ref and kernfs_mutex itself. kernfs_get/put_active() and
kernfs_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: Updated to fit the v2 restructuring of removal path.

Signed-off-by: Tejun Heo <tj@kernel.org>
---
fs/kernfs/dir.c | 114 ++++++++++----------------------------------
fs/kernfs/file.c | 10 +---
fs/kernfs/kernfs-internal.h | 12 +----
fs/kernfs/symlink.c | 10 +---
include/linux/kernfs.h | 4 --
5 files changed, 29 insertions(+), 121 deletions(-)

diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c
index f878e4f..770d687 100644
--- a/fs/kernfs/dir.c
+++ b/fs/kernfs/dir.c
@@ -399,28 +399,7 @@ struct kernfs_node *kernfs_new_node(struct kernfs_root *root, const char *name,
}

/**
- * 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
* @parent: the parent kernfs_node to add @kn to
*
@@ -428,34 +407,29 @@ void kernfs_addrm_start(struct kernfs_addrm_cxt *acxt)
* parent 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,
- struct kernfs_node *parent)
+int kernfs_add_one(struct kernfs_node *kn, struct kernfs_node *parent)
{
- bool has_ns = kernfs_ns_enabled(parent);
struct kernfs_iattrs *ps_iattr;
+ bool has_ns;
int ret;

- WARN_ON_ONCE(atomic_read(&parent->active) < 0);
+ if (!kernfs_get_active(parent))
+ return -ENOENT;

- 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;

kn->hash = kernfs_name_hash(kn->name, kn->ns);
kn->parent = parent;
@@ -463,7 +437,7 @@ int kernfs_add_one(struct kernfs_addrm_cxt *acxt, struct kernfs_node *kn,

ret = kernfs_link_sibling(kn);
if (ret)
- return ret;
+ goto out_unlock;

/* Update timestamps on the parent */
ps_iattr = parent->iattr;
@@ -474,34 +448,11 @@ int kernfs_add_one(struct kernfs_addrm_cxt *acxt, struct kernfs_node *kn,

/* Mark the entry added into directory tree */
atomic_sub(KN_DEACTIVATED_BIAS, &kn->active);
- 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);
- }
+ kernfs_put_active(parent);
+ return ret;
}

/**
@@ -633,7 +584,6 @@ 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;

@@ -648,14 +598,7 @@ struct kernfs_node *kernfs_create_dir_ns(struct kernfs_node *parent,
kn->priv = priv;

/* link in */
- rc = -ENOENT;
- if (kernfs_get_active(parent)) {
- kernfs_addrm_start(&acxt);
- rc = kernfs_add_one(&acxt, kn, parent);
- kernfs_addrm_finish(&acxt);
- kernfs_put_active(parent);
- }
-
+ rc = kernfs_add_one(kn, parent);
if (!rc)
return kn;

@@ -841,8 +784,7 @@ static void __kernfs_deactivate(struct kernfs_node *kn)
}
}

-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;

@@ -890,8 +832,7 @@ 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);
@@ -906,11 +847,9 @@ 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);
}

/**
@@ -925,7 +864,6 @@ 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) {
@@ -934,13 +872,13 @@ 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 404ffd2..ffe1beb 100644
--- a/fs/kernfs/file.c
+++ b/fs/kernfs/file.c
@@ -817,7 +817,6 @@ 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;
@@ -853,14 +852,7 @@ struct kernfs_node *__kernfs_create_file(struct kernfs_node *parent,
if (ops->mmap)
kn->flags |= KERNFS_HAS_MMAP;

- rc = -ENOENT;
- if (kernfs_get_active(parent)) {
- kernfs_addrm_start(&acxt);
- rc = kernfs_add_one(&acxt, kn, parent);
- kernfs_addrm_finish(&acxt);
- kernfs_put_active(parent);
- }
-
+ rc = kernfs_add_one(kn, parent);
if (rc) {
kernfs_put(kn);
return ERR_PTR(rc);
diff --git a/fs/kernfs/kernfs-internal.h b/fs/kernfs/kernfs-internal.h
index e9ec38c..4bc5784 100644
--- a/fs/kernfs/kernfs-internal.h
+++ b/fs/kernfs/kernfs-internal.h
@@ -46,13 +46,6 @@ 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 {
@@ -101,10 +94,7 @@ 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,
- struct kernfs_node *parent);
-void kernfs_addrm_finish(struct kernfs_addrm_cxt *acxt);
+int kernfs_add_one(struct kernfs_node *kn, struct kernfs_node *parent);
struct kernfs_node *kernfs_new_node(struct kernfs_root *root, const char *name,
umode_t mode, unsigned flags);

diff --git a/fs/kernfs/symlink.c b/fs/kernfs/symlink.c
index b2c106c..3a939c2 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(kernfs_root(parent), name, S_IFLNK|S_IRWXUGO,
@@ -40,14 +39,7 @@ struct kernfs_node *kernfs_create_link(struct kernfs_node *parent,
kn->symlink.target_kn = target;
kernfs_get(target); /* ref owned by symlink */

- error = -ENOENT;
- if (kernfs_get_active(parent)) {
- kernfs_addrm_start(&acxt);
- error = kernfs_add_one(&acxt, kn, parent);
- kernfs_addrm_finish(&acxt);
- kernfs_put_active(parent);
- }
-
+ error = kernfs_add_one(kn, parent);
if (!error)
return kn;

diff --git a/include/linux/kernfs.h b/include/linux/kernfs.h
index 61bd7ae..9b5a4bb 100644
--- a/include/linux/kernfs.h
+++ b/include/linux/kernfs.h
@@ -89,10 +89,6 @@ struct kernfs_node {

struct rb_node rb;

- union {
- struct kernfs_node *removed_list;
- } u;
-
const void *ns; /* namespace tag */
unsigned int hash; /* ns + name hash */
union {
--
1.8.4.2