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sysfs: Add s_hash to sysfs_dirent and order directory entries by hash

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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>
This commit is contained in:
Eric W. Biederman
2011-12-18 20:05:43 -08:00
committed by Greg Kroah-Hartman
parent dcd6c92267
commit 4e4d6d860b
2 changed files with 117 additions and 105 deletions
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9
fs/sysfs/sysfs.h
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@ -20,9 +20,8 @@ struct sysfs_elem_dir {
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 {
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 @@ struct sysfs_dirent {
} 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;