sysfs: use singly-linked list for sysfs_dirent tree
Make sysfs_dirent use singly linked list for its tree structure.
sysfs_link_sibling() and sysfs_unlink_sibling() functions are added to
handle simpler cases. It adds some complexity and cpu cycle overhead
but reduced memory footprint is worthwhile on big machines.
This change reduces the sizeof sysfs_dirent from 104 to 88 on 64bit
and from 60 to 52 on 32bit.
Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
diff --git a/fs/sysfs/inode.c b/fs/sysfs/inode.c
index 3eab9c4..732fd7f 100644
--- a/fs/sysfs/inode.c
+++ b/fs/sysfs/inode.c
@@ -284,8 +284,8 @@
int sysfs_hash_and_remove(struct dentry * dir, const char * name)
{
- struct sysfs_dirent * sd;
- struct sysfs_dirent * parent_sd;
+ struct sysfs_dirent **pos, *sd;
+ struct sysfs_dirent *parent_sd = dir->d_fsdata;
int found = 0;
if (!dir)
@@ -295,13 +295,15 @@
/* no inode means this hasn't been made visible yet */
return -ENOENT;
- parent_sd = dir->d_fsdata;
mutex_lock_nested(&dir->d_inode->i_mutex, I_MUTEX_PARENT);
- list_for_each_entry(sd, &parent_sd->s_children, s_sibling) {
+ for (pos = &parent_sd->s_children; *pos; pos = &(*pos)->s_sibling) {
+ sd = *pos;
+
if (!sd->s_type)
continue;
if (!strcmp(sd->s_name, name)) {
- list_del_init(&sd->s_sibling);
+ *pos = sd->s_sibling;
+ sd->s_sibling = NULL;
found = 1;
break;
}