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Date: Thu, 28 Nov 2013 14:54:40 -0500
From: Tejun Heo <tj@...nel.org>
To: gregkh@...uxfoundation.org
Cc: kay@...y.org, linux-kernel@...r.kernel.org, ebiederm@...ssion.com,
bhelgaas@...gle.com, Tejun Heo <tj@...nel.org>
Subject: [PATCH 27/34] sysfs, kernfs: implement kernfs_create/destroy_root()
There currently is single kernfs hierarchy in the whole system which
is used for sysfs. kernfs needs to support multiple hierarchies to
allow other users. This patch introduces struct kernfs_root which
serves as the root of each kernfs hierarchy and implements
kernfs_create/destroy_root().
* Each kernfs_root is associated with a root sd (sysfs_dentry). The
root is freed when the root sd is released and kernfs_destory_root()
simply invokes kernfs_remove() on the root sd. sysfs_remove_one()
is updated to handle release of the root sd. Note that ps_iattr
update in sysfs_remove_one() is trivially updated for readability.
* Root sd's are now dynamically allocated using sysfs_new_dirent().
Update sysfs_alloc_ino() so that it gives out ino from 1 so that the
root sd still gets ino 1.
* While kernfs currently only points to the root sd, it'll soon grow
fields which are specific to each hierarchy. As determining a given
sd's root will be necessary, sd->s_dir.root is added. This backlink
fits better as a separate field in sd; however, sd->s_dir is inside
union with space to spare, so use it to save space and provide
kernfs_root() accessor to determine the root sd.
* As hierarchies may be destroyed now, each mount needs to hold onto
the hierarchy it's attached to. Update sysfs_fill_super() and
sysfs_kill_sb() so that they get and put the kernfs_root
respectively.
* sysfs_root is replaced with kernfs_root which is dynamically created
by invoking kernfs_create_root() from sysfs_init().
This patch doesn't introduce any visible behavior changes.
v2: kernfs_create_root() forgot to set @sd->priv. Fixed.
Signed-off-by: Tejun Heo <tj@...nel.org>
---
fs/kernfs/dir.c | 71 +++++++++++++++++++++++++++++++++++++++------
fs/kernfs/kernfs-internal.h | 20 +++++++++++++
fs/sysfs/mount.c | 29 +++++++++++-------
include/linux/kernfs.h | 13 +++++++++
4 files changed, 113 insertions(+), 20 deletions(-)
diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c
index a4ca4de..246740a 100644
--- a/fs/kernfs/dir.c
+++ b/fs/kernfs/dir.c
@@ -211,7 +211,7 @@ static int sysfs_alloc_ino(unsigned int *pino)
retry:
spin_lock(&sysfs_ino_lock);
- rc = ida_get_new_above(&sysfs_ino_ida, 2, &ino);
+ rc = ida_get_new_above(&sysfs_ino_ida, 1, &ino);
spin_unlock(&sysfs_ino_lock);
if (rc == -EAGAIN) {
@@ -253,9 +253,11 @@ EXPORT_SYMBOL_GPL(kernfs_get);
void kernfs_put(struct sysfs_dirent *sd)
{
struct sysfs_dirent *parent_sd;
+ struct kernfs_root *root;
if (!sd || !atomic_dec_and_test(&sd->s_count))
return;
+ root = kernfs_root(sd);
repeat:
/* Moving/renaming is always done while holding reference.
* sd->s_parent won't change beneath us.
@@ -278,8 +280,13 @@ void kernfs_put(struct sysfs_dirent *sd)
kmem_cache_free(sysfs_dir_cachep, sd);
sd = parent_sd;
- if (sd && atomic_dec_and_test(&sd->s_count))
- goto repeat;
+ if (sd) {
+ if (atomic_dec_and_test(&sd->s_count))
+ goto repeat;
+ } else {
+ /* just released the root sd, free @root too */
+ kfree(root);
+ }
}
EXPORT_SYMBOL_GPL(kernfs_put);
@@ -493,13 +500,15 @@ static void sysfs_remove_one(struct sysfs_addrm_cxt *acxt,
if (sd->s_flags & SYSFS_FLAG_REMOVED)
return;
- sysfs_unlink_sibling(sd);
+ if (sd->s_parent) {
+ sysfs_unlink_sibling(sd);
- /* Update timestamps on the parent */
- ps_iattr = sd->s_parent->s_iattr;
- if (ps_iattr) {
- struct iattr *ps_iattrs = &ps_iattr->ia_iattr;
- ps_iattrs->ia_ctime = ps_iattrs->ia_mtime = CURRENT_TIME;
+ /* Update timestamps on the parent */
+ ps_iattr = sd->s_parent->s_iattr;
+ if (ps_iattr) {
+ ps_iattr->ia_iattr.ia_ctime = CURRENT_TIME;
+ ps_iattr->ia_iattr.ia_mtime = CURRENT_TIME;
+ }
}
sd->s_flags |= SYSFS_FLAG_REMOVED;
@@ -604,6 +613,49 @@ struct sysfs_dirent *kernfs_find_and_get_ns(struct sysfs_dirent *parent,
EXPORT_SYMBOL_GPL(kernfs_find_and_get_ns);
/**
+ * kernfs_create_root - create a new kernfs hierarchy
+ * @priv: opaque data associated with the new directory
+ *
+ * Returns the root of the new hierarchy on success, ERR_PTR() value on
+ * failure.
+ */
+struct kernfs_root *kernfs_create_root(void *priv)
+{
+ struct kernfs_root *root;
+ struct sysfs_dirent *sd;
+
+ root = kzalloc(sizeof(*root), GFP_KERNEL);
+ if (!root)
+ return ERR_PTR(-ENOMEM);
+
+ sd = sysfs_new_dirent("", S_IFDIR | S_IRUGO | S_IXUGO, SYSFS_DIR);
+ if (!sd) {
+ kfree(root);
+ return ERR_PTR(-ENOMEM);
+ }
+
+ sd->s_flags &= ~SYSFS_FLAG_REMOVED;
+ sd->priv = priv;
+ sd->s_dir.root = root;
+
+ root->sd = sd;
+
+ return root;
+}
+
+/**
+ * kernfs_destroy_root - destroy a kernfs hierarchy
+ * @root: root of the hierarchy to destroy
+ *
+ * Destroy the hierarchy anchored at @root by removing all existing
+ * directories and destroying @root.
+ */
+void kernfs_destroy_root(struct kernfs_root *root)
+{
+ kernfs_remove(root->sd); /* will also free @root */
+}
+
+/**
* kernfs_create_dir_ns - create a directory
* @parent: parent in which to create a new directory
* @name: name of the new directory
@@ -626,6 +678,7 @@ struct sysfs_dirent *kernfs_create_dir_ns(struct sysfs_dirent *parent,
if (!sd)
return ERR_PTR(-ENOMEM);
+ sd->s_dir.root = parent->s_dir.root;
sd->s_ns = ns;
sd->priv = priv;
diff --git a/fs/kernfs/kernfs-internal.h b/fs/kernfs/kernfs-internal.h
index 62ae35f..7dfe062 100644
--- a/fs/kernfs/kernfs-internal.h
+++ b/fs/kernfs/kernfs-internal.h
@@ -25,6 +25,12 @@ struct sysfs_elem_dir {
unsigned long subdirs;
/* children rbtree starts here and goes through sd->s_rb */
struct rb_root children;
+
+ /*
+ * The kernfs hierarchy this directory belongs to. This fits
+ * better directly in sysfs_dirent but is here to save space.
+ */
+ struct kernfs_root *root;
};
struct sysfs_elem_symlink {
@@ -104,6 +110,20 @@ static inline unsigned int sysfs_type(struct sysfs_dirent *sd)
return sd->s_flags & SYSFS_TYPE_MASK;
}
+/**
+ * kernfs_root - find out the kernfs_root a sysfs_dirent belongs to
+ * @sd: sysfs_dirent of interest
+ *
+ * Return the kernfs_root @sd belongs to.
+ */
+static inline struct kernfs_root *kernfs_root(struct sysfs_dirent *sd)
+{
+ /* if parent exists, it's always a dir; otherwise, @sd is a dir */
+ if (sd->s_parent)
+ sd = sd->s_parent;
+ return sd->s_dir.root;
+}
+
/*
* Context structure to be used while adding/removing nodes.
*/
diff --git a/fs/sysfs/mount.c b/fs/sysfs/mount.c
index 7cbd1fc..0b5661b 100644
--- a/fs/sysfs/mount.c
+++ b/fs/sysfs/mount.c
@@ -32,15 +32,8 @@ static const struct super_operations sysfs_ops = {
.evict_inode = sysfs_evict_inode,
};
-static struct sysfs_dirent sysfs_root = {
- .s_name = "",
- .s_count = ATOMIC_INIT(1),
- .s_flags = SYSFS_DIR,
- .s_mode = S_IFDIR | S_IRUGO | S_IXUGO,
- .s_ino = 1,
-};
-
-struct sysfs_dirent *sysfs_root_sd = &sysfs_root;
+static struct kernfs_root *sysfs_root;
+struct sysfs_dirent *sysfs_root_sd;
static int sysfs_fill_super(struct super_block *sb)
{
@@ -68,6 +61,7 @@ static int sysfs_fill_super(struct super_block *sb)
pr_debug("%s: could not get root dentry!\n", __func__);
return -ENOMEM;
}
+ kernfs_get(sysfs_root_sd);
root->d_fsdata = sysfs_root_sd;
sb->s_root = root;
sb->s_d_op = &sysfs_dentry_ops;
@@ -138,11 +132,15 @@ static struct dentry *sysfs_mount(struct file_system_type *fs_type,
static void sysfs_kill_sb(struct super_block *sb)
{
struct sysfs_super_info *info = sysfs_info(sb);
- /* Remove the superblock from fs_supers/s_instances
+ struct sysfs_dirent *root_sd = sb->s_root->d_fsdata;
+
+ /*
+ * Remove the superblock from fs_supers/s_instances
* so we can't find it, before freeing sysfs_super_info.
*/
kill_anon_super(sb);
free_sysfs_super_info(info);
+ kernfs_put(root_sd);
}
static struct file_system_type sysfs_fs_type = {
@@ -166,12 +164,21 @@ int __init sysfs_init(void)
if (err)
goto out_err;
+ sysfs_root = kernfs_create_root(NULL);
+ if (IS_ERR(sysfs_root)) {
+ err = PTR_ERR(sysfs_root);
+ goto out_err;
+ }
+ sysfs_root_sd = sysfs_root->sd;
+
err = register_filesystem(&sysfs_fs_type);
if (err)
- goto out_err;
+ goto out_destroy_root;
return 0;
+out_destroy_root:
+ kernfs_destroy_root(sysfs_root);
out_err:
kmem_cache_destroy(sysfs_dir_cachep);
sysfs_dir_cachep = NULL;
diff --git a/include/linux/kernfs.h b/include/linux/kernfs.h
index fd8f574..f75548b 100644
--- a/include/linux/kernfs.h
+++ b/include/linux/kernfs.h
@@ -20,6 +20,11 @@ struct vm_area_struct;
struct sysfs_dirent;
+struct kernfs_root {
+ /* published fields */
+ struct sysfs_dirent *sd;
+};
+
struct sysfs_open_file {
/* published fields */
struct sysfs_dirent *sd;
@@ -76,6 +81,9 @@ struct sysfs_dirent *kernfs_find_and_get_ns(struct sysfs_dirent *parent,
void kernfs_get(struct sysfs_dirent *sd);
void kernfs_put(struct sysfs_dirent *sd);
+struct kernfs_root *kernfs_create_root(void *priv);
+void kernfs_destroy_root(struct kernfs_root *root);
+
struct sysfs_dirent *kernfs_create_dir_ns(struct sysfs_dirent *parent,
const char *name, void *priv,
const void *ns);
@@ -107,6 +115,11 @@ kernfs_find_and_get_ns(struct sysfs_dirent *parent, const char *name,
static inline void kernfs_get(struct sysfs_dirent *sd) { }
static inline void kernfs_put(struct sysfs_dirent *sd) { }
+static inline struct kernfs_root *kernfs_create_root(void *priv)
+{ return ERR_PTR(-ENOSYS); }
+
+static inline void kernfs_destroy_root(struct kernfs_root *root) { }
+
static inline struct sysfs_dirent *
kernfs_create_dir_ns(struct sysfs_dirent *parent, const char *name, void *priv,
const void *ns)
--
1.8.4.2
--
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