sysfs: create optimal relative symlink targets

[linux-2.6-omap-h63xx.git] / fs / sysfs / symlink.c

diff --git a/fs/sysfs/symlink.c b/fs/sysfs/symlink.c
index 4ce687f0b5d01751dfb8f8aa189c84360eaab39e..5f66c446615176eff46e1864a7343f228bac19e6 100644 (file)
--- a/fs/sysfs/symlink.c
+++ b/fs/sysfs/symlink.c
@@ -1,5 +1,13 @@
 /*
- * symlink.c - operations for sysfs symlinks.
+ * fs/sysfs/symlink.c - sysfs symlink implementation
+ *
+ * Copyright (c) 2001-3 Patrick Mochel
+ * Copyright (c) 2007 SUSE Linux Products GmbH
+ * Copyright (c) 2007 Tejun Heo <teheo@suse.de>
+ *
+ * This file is released under the GPLv2.
+ *
+ * Please see Documentation/filesystems/sysfs.txt for more information.
  */
 
 #include <linux/fs.h>
@@ -7,43 +15,10 @@
 #include <linux/module.h>
 #include <linux/kobject.h>
 #include <linux/namei.h>
-#include <asm/semaphore.h>
+#include <linux/mutex.h>
 
 #include "sysfs.h"
 
-static int object_depth(struct sysfs_dirent *sd)
-{
-       int depth = 0;
-
-       for (; sd->s_parent; sd = sd->s_parent)
-               depth++;
-
-       return depth;
-}
-
-static int object_path_length(struct sysfs_dirent * sd)
-{
-       int length = 1;
-
-       for (; sd->s_parent; sd = sd->s_parent)
-               length += strlen(sd->s_name) + 1;
-
-       return length;
-}
-
-static void fill_object_path(struct sysfs_dirent *sd, char *buffer, int length)
-{
-       --length;
-       for (; sd->s_parent; sd = sd->s_parent) {
-               int cur = strlen(sd->s_name);
-
-               /* back up enough to print this bus id with '/' */
-               length -= cur;
-               strncpy(buffer + length, sd->s_name, cur);
-               *(buffer + --length) = '/';
-       }
-}
-
 /**
  *     sysfs_create_link - create symlink between two objects.
  *     @kobj:  object whose directory we're creating the link in.
@@ -60,10 +35,9 @@ int sysfs_create_link(struct kobject * kobj, struct kobject * target, const char
 
        BUG_ON(!name);
 
-       if (!kobj) {
-               if (sysfs_mount && sysfs_mount->mnt_sb)
-                       parent_sd = sysfs_mount->mnt_sb->s_root->d_fsdata;
-       } else
+       if (!kobj)
+               parent_sd = &sysfs_root;
+       else
                parent_sd = kobj->sd;
 
        error = -EFAULT;
@@ -87,20 +61,15 @@ int sysfs_create_link(struct kobject * kobj, struct kobject * target, const char
        if (!sd)
                goto out_put;
 
-       sd->s_elem.symlink.target_sd = target_sd;
+       sd->s_symlink.target_sd = target_sd;
        target_sd = NULL;       /* reference is now owned by the symlink */
 
        sysfs_addrm_start(&acxt, parent_sd);
+       error = sysfs_add_one(&acxt, sd);
+       sysfs_addrm_finish(&acxt);
 
-       if (!sysfs_find_dirent(parent_sd, name)) {
-               sysfs_add_one(&acxt, sd);
-               sysfs_link_sibling(sd);
-       }
-
-       if (!sysfs_addrm_finish(&acxt)) {
-               error = -EEXIST;
+       if (error)
                goto out_put;
-       }
 
        return 0;
 
@@ -110,7 +79,6 @@ int sysfs_create_link(struct kobject * kobj, struct kobject * target, const char
        return error;
 }
 
-
 /**
  *     sysfs_remove_link - remove symlink in object's directory.
  *     @kobj:  object we're acting for.
@@ -122,24 +90,54 @@ void sysfs_remove_link(struct kobject * kobj, const char * name)
        sysfs_hash_and_remove(kobj->sd, name);
 }
 
-static int sysfs_get_target_path(struct sysfs_dirent * parent_sd,
-                                struct sysfs_dirent * target_sd, char *path)
+static int sysfs_get_target_path(struct sysfs_dirent *parent_sd,
+                                struct sysfs_dirent *target_sd, char *path)
 {
-       char * s;
-       int depth, size;
+       struct sysfs_dirent *base, *sd;
+       char *s = path;
+       int len = 0;
+
+       /* go up to the root, stop at the base */
+       base = parent_sd;
+       while (base->s_parent) {
+               sd = target_sd->s_parent;
+               while (sd->s_parent && base != sd)
+                       sd = sd->s_parent;
+
+               if (base == sd)
+                       break;
+
+               strcpy(s, "../");
+               s += 3;
+               base = base->s_parent;
+       }
 
-       depth = object_depth(parent_sd);
-       size = object_path_length(target_sd) + depth * 3 - 1;
-       if (size > PATH_MAX)
+       /* determine end of target string for reverse fillup */
+       sd = target_sd;
+       while (sd->s_parent && sd != base) {
+               len += strlen(sd->s_name) + 1;
+               sd = sd->s_parent;
+       }
+
+       /* check limits */
+       if (len < 2)
+               return -EINVAL;
+       len--;
+       if ((s - path) + len > PATH_MAX)
                return -ENAMETOOLONG;
 
-       pr_debug("%s: depth = %d, size = %d\n", __FUNCTION__, depth, size);
+       /* reverse fillup of target string from target to base */
+       sd = target_sd;
+       while (sd->s_parent && sd != base) {
+               int slen = strlen(sd->s_name);
 
-       for (s = path; depth--; s += 3)
-               strcpy(s,"../");
+               len -= slen;
+               strncpy(s + len, sd->s_name, slen);
+               if (len)
+                       s[--len] = '/';
 
-       fill_object_path(target_sd, path, size);
-       pr_debug("%s: path = '%s'\n", __FUNCTION__, path);
+               sd = sd->s_parent;
+       }
 
        return 0;
 }
@@ -148,7 +146,7 @@ static int sysfs_getlink(struct dentry *dentry, char * path)
 {
        struct sysfs_dirent *sd = dentry->d_fsdata;
        struct sysfs_dirent *parent_sd = sd->s_parent;
-       struct sysfs_dirent *target_sd = sd->s_elem.symlink.target_sd;
+       struct sysfs_dirent *target_sd = sd->s_symlink.target_sd;
        int error;
 
        mutex_lock(&sysfs_mutex);