sysfs: Add s_hash to sysfs_dirent and order directory entries by hash
Compute a 31 bit hash of directory entries (that can fit in a signed
32bit off_t) and index the sysfs directory entries by that hash,
replacing the per directory indexes by name and by inode. Because we
now only use a single rbtree this reduces the size of sysfs_dirent by 2
pointers. Because we have fewer cases to deal with the code is now
simpler.
For now I use the simple hash that the dcache uses as that is easy to
use and seems simple enough.
In addition to makeing the code simpler using a hash for the file
position in readdir brings sysfs in line with other filesystems that
have non-trivial directory structures.
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
diff --git a/fs/sysfs/sysfs.h b/fs/sysfs/sysfs.h
index 7484a36..2b5c923 100644
--- a/fs/sysfs/sysfs.h
+++ b/fs/sysfs/sysfs.h
@@ -20,9 +20,8 @@
struct kobject *kobj;
unsigned long subdirs;
-
- struct rb_root inode_tree;
- struct rb_root name_tree;
+ /* children rbtree starts here and goes through sd->s_rb */
+ struct rb_root children;
};
struct sysfs_elem_symlink {
@@ -62,8 +61,7 @@
struct sysfs_dirent *s_parent;
const char *s_name;
- struct rb_node inode_node;
- struct rb_node name_node;
+ struct rb_node s_rb;
union {
struct completion *completion;
@@ -71,6 +69,7 @@
} u;
const void *s_ns; /* namespace tag */
+ unsigned int s_hash; /* ns + name hash */
union {
struct sysfs_elem_dir s_dir;
struct sysfs_elem_symlink s_symlink;