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kernfs: implement kernfs_walk_and_get()

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Implement kernfs_walk_and_get() which is similar to
kernfs_find_and_get() but can walk a path instead of just a name.

v2: Use strlcpy() instead of strlen() + memcpy() as suggested by
    David.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: David Miller <davem@davemloft.net>
This commit is contained in:
Tejun Heo 2015-11-20 15:55:52 -05:00
parent b11cfb5807
commit bd96f76a24
2 changed files with 58 additions and 0 deletions
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46
fs/kernfs/dir.c
View File

@ -694,6 +694,29 @@ static struct kernfs_node *kernfs_find_ns(struct kernfs_node *parent,
return NULL;
}
static struct kernfs_node *kernfs_walk_ns(struct kernfs_node *parent,
const unsigned char *path,
const void *ns)
{
static char path_buf[PATH_MAX]; /* protected by kernfs_mutex */
size_t len = strlcpy(path_buf, path, PATH_MAX);
char *p = path_buf;
char *name;
lockdep_assert_held(&kernfs_mutex);
if (len >= PATH_MAX)
return NULL;
while ((name = strsep(&p, "/")) && parent) {
if (*name == '\0')
continue;
parent = kernfs_find_ns(parent, name, ns);
}
return parent;
}
/**
* kernfs_find_and_get_ns - find and get kernfs_node with the given name
* @parent: kernfs_node to search under
@ -718,6 +741,29 @@ struct kernfs_node *kernfs_find_and_get_ns(struct kernfs_node *parent,
}
EXPORT_SYMBOL_GPL(kernfs_find_and_get_ns);
/**
* kernfs_walk_and_get_ns - find and get kernfs_node with the given path
* @parent: kernfs_node to search under
* @path: path to look for
* @ns: the namespace tag to use
*
* Look for kernfs_node with path @path under @parent and get a reference
* if found. This function may sleep and returns pointer to the found
* kernfs_node on success, %NULL on failure.
*/
struct kernfs_node *kernfs_walk_and_get_ns(struct kernfs_node *parent,
const char *path, const void *ns)
{
struct kernfs_node *kn;
mutex_lock(&kernfs_mutex);
kn = kernfs_walk_ns(parent, path, ns);
kernfs_get(kn);
mutex_unlock(&kernfs_mutex);
return kn;
}
/**
* kernfs_create_root - create a new kernfs hierarchy
* @scops: optional syscall operations for the hierarchy

12
include/linux/kernfs.h
View File

@ -274,6 +274,8 @@ void pr_cont_kernfs_path(struct kernfs_node *kn);
struct kernfs_node *kernfs_get_parent(struct kernfs_node *kn);
struct kernfs_node *kernfs_find_and_get_ns(struct kernfs_node *parent,
const char *name, const void *ns);
struct kernfs_node *kernfs_walk_and_get_ns(struct kernfs_node *parent,
const char *path, const void *ns);
void kernfs_get(struct kernfs_node *kn);
void kernfs_put(struct kernfs_node *kn);
@ -350,6 +352,10 @@ static inline struct kernfs_node *
kernfs_find_and_get_ns(struct kernfs_node *parent, const char *name,
const void *ns)
{ return NULL; }
static inline struct kernfs_node *
kernfs_walk_and_get_ns(struct kernfs_node *parent, const char *path,
const void *ns)
{ return NULL; }
static inline void kernfs_get(struct kernfs_node *kn) { }
static inline void kernfs_put(struct kernfs_node *kn) { }
@ -430,6 +436,12 @@ kernfs_find_and_get(struct kernfs_node *kn, const char *name)
return kernfs_find_and_get_ns(kn, name, NULL);
}
static inline struct kernfs_node *
kernfs_walk_and_get(struct kernfs_node *kn, const char *path)
{
return kernfs_walk_and_get_ns(kn, path, NULL);
}
static inline struct kernfs_node *
kernfs_create_dir(struct kernfs_node *parent, const char *name, umode_t mode,
void *priv)