sysfs: implement sysfs_find_dirent() and sysfs_get_dirent()

Implement sysfs_find_dirent() and sysfs_get_dirent().
sysfs_dirent_exist() is replaced by sysfs_find_dirent().  These will
be used to make directory entries reclamiable.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

4 files changed, 50 insertions, 20 deletions

diff --git a/fs/sysfs/dir.c b/fs/sysfs/dir.c
index f2ea00683ec9..4762a9aa0b27 100644
--- a/fs/sysfs/dir.c
+++ b/fs/sysfs/dir.c
@@ -317,28 +317,55 @@ void sysfs_attach_dirent(struct sysfs_dirent *sd,
         }
 }
 
-/*
+/**
+ *      sysfs_find_dirent - find sysfs_dirent with the given name
+ *      @parent_sd: sysfs_dirent to search under
+ *      @name: name to look for
  *
- * Return -EEXIST if there is already a sysfs element with the same name for
- * the same parent.
+ *      Look for sysfs_dirent with name @name under @parent_sd.
  *
- * called with parent inode's i_mutex held
+ *      LOCKING:
+ *      mutex_lock(parent->i_mutex)
+ *
+ *      RETURNS:
+ *      Pointer to sysfs_dirent if found, NULL if not.
  */
-int sysfs_dirent_exist(struct sysfs_dirent *parent_sd,
-                          const unsigned char *new)
+struct sysfs_dirent *sysfs_find_dirent(struct sysfs_dirent *parent_sd,
+                                       const unsigned char *name)
 {
-        struct sysfs_dirent * sd;
+        struct sysfs_dirent *sd;
 
-        for (sd = parent_sd->s_children; sd; sd = sd->s_sibling) {
-                if (sysfs_type(sd)) {
-                        if (strcmp(sd->s_name, new))
-                                continue;
-                        else
-                                return -EEXIST;
-                }
-        }
+        for (sd = parent_sd->s_children; sd; sd = sd->s_sibling)
+                if (sysfs_type(sd) && !strcmp(sd->s_name, name))
+                        return sd;
+        return NULL;
+}
 
-        return 0;
+/**
+ *      sysfs_get_dirent - find and get sysfs_dirent with the given name
+ *      @parent_sd: sysfs_dirent to search under
+ *      @name: name to look for
+ *
+ *      Look for sysfs_dirent with name @name under @parent_sd and get
+ *      it if found.
+ *
+ *      LOCKING:
+ *      Kernel thread context (may sleep)
+ *
+ *      RETURNS:
+ *      Pointer to sysfs_dirent if found, NULL if not.
+ */
+struct sysfs_dirent *sysfs_get_dirent(struct sysfs_dirent *parent_sd,
+                                      const unsigned char *name)
+{
+        struct sysfs_dirent *sd;
+
+        mutex_lock(&parent_sd->s_dentry->d_inode->i_mutex);
+        sd = sysfs_find_dirent(parent_sd, name);
+        sysfs_get(sd);
+        mutex_unlock(&parent_sd->s_dentry->d_inode->i_mutex);
+
+        return sd;
 }
 
 static int create_dir(struct kobject *kobj, struct dentry *parent,
@@ -382,7 +409,7 @@ static int create_dir(struct kobject *kobj, struct dentry *parent,
 
         /* link in */
         error = -EEXIST;
-        if (sysfs_dirent_exist(parent->d_fsdata, name))
+        if (sysfs_find_dirent(parent->d_fsdata, name))
                 goto out_iput;
 
         sysfs_instantiate(dentry, inode);
diff --git a/fs/sysfs/file.c b/fs/sysfs/file.c
index a84b734f7b29..e448b88e313e 100644
--- a/fs/sysfs/file.c
+++ b/fs/sysfs/file.c
@@ -421,7 +421,7 @@ int sysfs_add_file(struct dentry * dir, const struct attribute * attr, int type)
 
         mutex_lock(&dir->d_inode->i_mutex);
 
-        if (sysfs_dirent_exist(parent_sd, attr->name)) {
+        if (sysfs_find_dirent(parent_sd, attr->name)) {
                 error = -EEXIST;
                 goto out_unlock;
         }
diff --git a/fs/sysfs/symlink.c b/fs/sysfs/symlink.c
index ff605d3f4d33..45b62e229627 100644
--- a/fs/sysfs/symlink.c
+++ b/fs/sysfs/symlink.c
@@ -95,7 +95,7 @@ int sysfs_create_link(struct kobject * kobj, struct kobject * target, const char
                 return -ENOENT;
 
         mutex_lock(&dentry->d_inode->i_mutex);
-        if (!sysfs_dirent_exist(dentry->d_fsdata, name))
+        if (!sysfs_find_dirent(dentry->d_fsdata, name))
                 error = sysfs_add_link(parent_sd, name, target_sd);
         mutex_unlock(&dentry->d_inode->i_mutex);
 
diff --git a/fs/sysfs/sysfs.h b/fs/sysfs/sysfs.h
index 06b5085804a1..f1629b4520aa 100644
--- a/fs/sysfs/sysfs.h
+++ b/fs/sysfs/sysfs.h
@@ -59,7 +59,10 @@ extern struct inode * sysfs_get_inode(struct sysfs_dirent *sd);
 extern void sysfs_instantiate(struct dentry *dentry, struct inode *inode);
 
 extern void release_sysfs_dirent(struct sysfs_dirent * sd);
-extern int sysfs_dirent_exist(struct sysfs_dirent *, const unsigned char *);
+extern struct sysfs_dirent *sysfs_find_dirent(struct sysfs_dirent *parent_sd,
+                                              const unsigned char *name);
+extern struct sysfs_dirent *sysfs_get_dirent(struct sysfs_dirent *parent_sd,
+                                             const unsigned char *name);
 extern struct sysfs_dirent *sysfs_new_dirent(const char *name, umode_t mode,
                                              int type);
 extern void sysfs_attach_dirent(struct sysfs_dirent *sd,