From kay.sievers@vrfy.org Thu Nov 1 12:18:37 2007 From: Kay Sievers Date: Thu, 01 Nov 2007 20:20:52 +0100 Subject: sysfs: create optimal relative symlink targets To: Greg KH Cc: Denis Cheng , linux-kernel@vger.kernel.org Message-ID: <1193944852.2860.29.camel@lov.site> From: Kay Sievers Subject: sysfs: create optimal relative symlink targets Instead of walking from the source down to the root of sysfs, and back to the target, we stop at the first directory the source and the target share. This link: /devices/pci0000:00/0000:00:1d.7/usb1/1-0:1.0/ep_81 pointed to: ../../../../../devices/pci0000:00/0000:00:1d.0/usb2/2-0:1.0/usb_endpoint/usbdev2.1_ep81 now it just points to: usb_endpoint/usbdev1.1_ep81 Thanks to Denis Cheng for bringing this up, and sending the initial patch. CC: Denis Cheng Signed-off-by: Kay Sievers Signed-off-by: Greg Kroah-Hartman --- fs/sysfs/symlink.c | 90 +++++++++++++++++++++++++---------------------------- 1 file changed, 43 insertions(+), 47 deletions(-) --- a/fs/sysfs/symlink.c +++ b/fs/sysfs/symlink.c @@ -19,39 +19,6 @@ #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. @@ -112,7 +79,6 @@ int sysfs_create_link(struct kobject * k return error; } - /** * sysfs_remove_link - remove symlink in object's directory. * @kobj: object we're acting for. @@ -124,24 +90,54 @@ void sysfs_remove_link(struct kobject * 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) - return -ENAMETOOLONG; + /* 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; + } - pr_debug("%s: depth = %d, size = %d\n", __FUNCTION__, depth, size); + /* check limits */ + if (len < 2) + return -EINVAL; + len--; + if ((s - path) + len > PATH_MAX) + return -ENAMETOOLONG; - for (s = path; depth--; s += 3) - strcpy(s,"../"); + /* reverse fillup of target string from target to base */ + sd = target_sd; + while (sd->s_parent && sd != base) { + int slen = strlen(sd->s_name); + + 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; }