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sysfs, kernfs: implement kernfs_create/destroy_root()

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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@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Tejun Heo 2013-11-28 14:54:40 -05:00 committed by Greg Kroah-Hartman
parent 061447a496
commit ba7443bc65
4 changed files with 113 additions and 20 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

61
fs/kernfs/dir.c
View File

@ -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))
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;
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;
ps_iattr->ia_iattr.ia_ctime = CURRENT_TIME;
ps_iattr->ia_iattr.ia_mtime = CURRENT_TIME;
}
}
sd->s_flags |= SYSFS_FLAG_REMOVED;
@ -603,6 +612,49 @@ 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
@ -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;

20
fs/kernfs/kernfs-internal.h
View File

@ -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.
*/

29
fs/sysfs/mount.c
View File

@ -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;

13
include/linux/kernfs.h
View File

@ -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)