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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>
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Eric W. Biederman authored and Greg Kroah-Hartman committed Jan 24, 2012
1 parent dcd6c92 commit 4e4d6d8
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Showing 2 changed files with 120 additions and 108 deletions.
219 changes: 116 additions & 103 deletions fs/sysfs/dir.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -22,76 +22,103 @@
#include <linux/mutex.h>
#include <linux/slab.h>
#include <linux/security.h>
#include <linux/hash.h>
#include "sysfs.h"

DEFINE_MUTEX(sysfs_mutex);
DEFINE_SPINLOCK(sysfs_assoc_lock);

#define to_sysfs_dirent(X) rb_entry((X), struct sysfs_dirent, s_rb);

static DEFINE_SPINLOCK(sysfs_ino_lock);
static DEFINE_IDA(sysfs_ino_ida);

/**
* sysfs_link_sibling - link sysfs_dirent into sibling list
* sysfs_name_hash
* @ns: Namespace tag to hash
* @name: Null terminated string to hash
*
* Returns 31 bit hash of ns + name (so it fits in an off_t )
*/
static unsigned int sysfs_name_hash(const void *ns, const char *name)
{
unsigned long hash = init_name_hash();
unsigned int len = strlen(name);
while (len--)
hash = partial_name_hash(*name++, hash);
hash = ( end_name_hash(hash) ^ hash_ptr( (void *)ns, 31 ) );
hash &= 0x7fffffffU;
/* Reserve hash numbers 0, 1 and INT_MAX for magic directory entries */
if (hash < 1)
hash += 2;
if (hash >= INT_MAX)
hash = INT_MAX - 1;
return hash;
}

static int sysfs_name_compare(unsigned int hash, const void *ns,
const char *name, const struct sysfs_dirent *sd)
{
if (hash != sd->s_hash)
return hash - sd->s_hash;
if (ns != sd->s_ns)
return ns - sd->s_ns;
return strcmp(name, sd->s_name);
}

static int sysfs_sd_compare(const struct sysfs_dirent *left,
const struct sysfs_dirent *right)
{
return sysfs_name_compare(left->s_hash, left->s_ns, left->s_name,
right);
}

/**
* sysfs_link_subling - link sysfs_dirent into sibling rbtree
* @sd: sysfs_dirent of interest
*
* Link @sd into its sibling list which starts from
* Link @sd into its sibling rbtree which starts from
* sd->s_parent->s_dir.children.
*
* Locking:
* mutex_lock(sysfs_mutex)
*
* RETURNS:
* 0 on susccess -EEXIST on failure.
*/
static void sysfs_link_sibling(struct sysfs_dirent *sd)
static int sysfs_link_sibling(struct sysfs_dirent *sd)
{
struct sysfs_dirent *parent_sd = sd->s_parent;

struct rb_node **p;
struct rb_node *parent;
struct rb_node **node = &sd->s_parent->s_dir.children.rb_node;
struct rb_node *parent = NULL;

if (sysfs_type(sd) == SYSFS_DIR)
parent_sd->s_dir.subdirs++;

p = &parent_sd->s_dir.inode_tree.rb_node;
parent = NULL;
while (*p) {
parent = *p;
#define node rb_entry(parent, struct sysfs_dirent, inode_node)
if (sd->s_ino < node->s_ino) {
p = &node->inode_node.rb_left;
} else if (sd->s_ino > node->s_ino) {
p = &node->inode_node.rb_right;
} else {
printk(KERN_CRIT "sysfs: inserting duplicate inode '%lx'\n",
(unsigned long) sd->s_ino);
BUG();
}
#undef node
}
rb_link_node(&sd->inode_node, parent, p);
rb_insert_color(&sd->inode_node, &parent_sd->s_dir.inode_tree);

p = &parent_sd->s_dir.name_tree.rb_node;
parent = NULL;
while (*p) {
int c;
parent = *p;
#define node rb_entry(parent, struct sysfs_dirent, name_node)
c = strcmp(sd->s_name, node->s_name);
if (c < 0) {
p = &node->name_node.rb_left;
} else {
p = &node->name_node.rb_right;
}
#undef node
sd->s_parent->s_dir.subdirs++;

while (*node) {
struct sysfs_dirent *pos;
int result;

pos = to_sysfs_dirent(*node);
parent = *node;
result = sysfs_sd_compare(sd, pos);
if (result < 0)
node = &pos->s_rb.rb_left;
else if (result > 0)
node = &pos->s_rb.rb_right;
else
return -EEXIST;
}
rb_link_node(&sd->name_node, parent, p);
rb_insert_color(&sd->name_node, &parent_sd->s_dir.name_tree);
/* add new node and rebalance the tree */
rb_link_node(&sd->s_rb, parent, node);
rb_insert_color(&sd->s_rb, &sd->s_parent->s_dir.children);
return 0;
}

/**
* sysfs_unlink_sibling - unlink sysfs_dirent from sibling list
* sysfs_unlink_sibling - unlink sysfs_dirent from sibling rbtree
* @sd: sysfs_dirent of interest
*
* Unlink @sd from its sibling list which starts from
* Unlink @sd from its sibling rbtree which starts from
* sd->s_parent->s_dir.children.
*
* Locking:
Expand All @@ -102,8 +129,7 @@ static void sysfs_unlink_sibling(struct sysfs_dirent *sd)
if (sysfs_type(sd) == SYSFS_DIR)
sd->s_parent->s_dir.subdirs--;

rb_erase(&sd->inode_node, &sd->s_parent->s_dir.inode_tree);
rb_erase(&sd->name_node, &sd->s_parent->s_dir.name_tree);
rb_erase(&sd->s_rb, &sd->s_parent->s_dir.children);
}

/**
Expand Down Expand Up @@ -402,6 +428,7 @@ void sysfs_addrm_start(struct sysfs_addrm_cxt *acxt,
int __sysfs_add_one(struct sysfs_addrm_cxt *acxt, struct sysfs_dirent *sd)
{
struct sysfs_inode_attrs *ps_iattr;
int ret;

if (!!sysfs_ns_type(acxt->parent_sd) != !!sd->s_ns) {
WARN(1, KERN_WARNING "sysfs: ns %s in '%s' for '%s'\n",
Expand All @@ -410,12 +437,12 @@ int __sysfs_add_one(struct sysfs_addrm_cxt *acxt, struct sysfs_dirent *sd)
return -EINVAL;
}

if (sysfs_find_dirent(acxt->parent_sd, sd->s_ns, sd->s_name))
return -EEXIST;

sd->s_hash = sysfs_name_hash(sd->s_ns, sd->s_name);
sd->s_parent = sysfs_get(acxt->parent_sd);

sysfs_link_sibling(sd);
ret = sysfs_link_sibling(sd);
if (ret)
return ret;

/* Update timestamps on the parent */
ps_iattr = acxt->parent_sd->s_iattr;
Expand Down Expand Up @@ -565,8 +592,8 @@ struct sysfs_dirent *sysfs_find_dirent(struct sysfs_dirent *parent_sd,
const void *ns,
const unsigned char *name)
{
struct rb_node *p = parent_sd->s_dir.name_tree.rb_node;
struct sysfs_dirent *found = NULL;
struct rb_node *node = parent_sd->s_dir.children.rb_node;
unsigned int hash;

if (!!sysfs_ns_type(parent_sd) != !!ns) {
WARN(1, KERN_WARNING "sysfs: ns %s in '%s' for '%s'\n",
Expand All @@ -575,33 +602,21 @@ struct sysfs_dirent *sysfs_find_dirent(struct sysfs_dirent *parent_sd,
return NULL;
}

while (p) {
int c;
#define node rb_entry(p, struct sysfs_dirent, name_node)
c = strcmp(name, node->s_name);
if (c < 0) {
p = node->name_node.rb_left;
} else if (c > 0) {
p = node->name_node.rb_right;
} else {
found = node;
p = node->name_node.rb_left;
}
#undef node
}

if (found) {
while (found->s_ns != ns) {
p = rb_next(&found->name_node);
if (!p)
return NULL;
found = rb_entry(p, struct sysfs_dirent, name_node);
if (strcmp(name, found->s_name))
return NULL;
}
hash = sysfs_name_hash(ns, name);
while (node) {
struct sysfs_dirent *sd;
int result;

sd = to_sysfs_dirent(node);
result = sysfs_name_compare(hash, ns, name, sd);
if (result < 0)
node = node->rb_left;
else if (result > 0)
node = node->rb_right;
else
return sd;
}

return found;
return NULL;
}

/**
Expand Down Expand Up @@ -804,9 +819,9 @@ static void __sysfs_remove_dir(struct sysfs_dirent *dir_sd)

pr_debug("sysfs %s: removing dir\n", dir_sd->s_name);
sysfs_addrm_start(&acxt, dir_sd);
pos = rb_first(&dir_sd->s_dir.inode_tree);
pos = rb_first(&dir_sd->s_dir.children);
while (pos) {
struct sysfs_dirent *sd = rb_entry(pos, struct sysfs_dirent, inode_node);
struct sysfs_dirent *sd = to_sysfs_dirent(pos);
pos = rb_next(pos);
if (sysfs_type(sd) != SYSFS_DIR)
sysfs_remove_one(&acxt, sd);
Expand Down Expand Up @@ -919,38 +934,36 @@ static int sysfs_dir_release(struct inode *inode, struct file *filp)
}

static struct sysfs_dirent *sysfs_dir_pos(const void *ns,
struct sysfs_dirent *parent_sd, ino_t ino, struct sysfs_dirent *pos)
struct sysfs_dirent *parent_sd, loff_t hash, struct sysfs_dirent *pos)
{
if (pos) {
int valid = !(pos->s_flags & SYSFS_FLAG_REMOVED) &&
pos->s_parent == parent_sd &&
ino == pos->s_ino;
hash == pos->s_hash;
sysfs_put(pos);
if (!valid)
pos = NULL;
}
if (!pos && (ino > 1) && (ino < INT_MAX)) {
struct rb_node *p = parent_sd->s_dir.inode_tree.rb_node;
while (p) {
#define node rb_entry(p, struct sysfs_dirent, inode_node)
if (ino < node->s_ino) {
pos = node;
p = node->inode_node.rb_left;
} else if (ino > node->s_ino) {
p = node->inode_node.rb_right;
} else {
pos = node;
if (!pos && (hash > 1) && (hash < INT_MAX)) {
struct rb_node *node = parent_sd->s_dir.children.rb_node;
while (node) {
pos = to_sysfs_dirent(node);

if (hash < pos->s_hash)
node = node->rb_left;
else if (hash > pos->s_hash)
node = node->rb_right;
else
break;
}
#undef node
}
}
/* Skip over entries in the wrong namespace */
while (pos && pos->s_ns != ns) {
struct rb_node *p = rb_next(&pos->inode_node);
if (!p)
struct rb_node *node = rb_next(&pos->s_rb);
if (!node)
pos = NULL;
else
pos = rb_entry(p, struct sysfs_dirent, inode_node);
pos = to_sysfs_dirent(node);
}
return pos;
}
Expand All @@ -960,11 +973,11 @@ static struct sysfs_dirent *sysfs_dir_next_pos(const void *ns,
{
pos = sysfs_dir_pos(ns, parent_sd, ino, pos);
if (pos) do {
struct rb_node *p = rb_next(&pos->inode_node);
if (!p)
struct rb_node *node = rb_next(&pos->s_rb);
if (!node)
pos = NULL;
else
pos = rb_entry(p, struct sysfs_dirent, inode_node);
pos = to_sysfs_dirent(node);
} while (pos && pos->s_ns != ns);
return pos;
}
Expand Down Expand Up @@ -1006,7 +1019,7 @@ static int sysfs_readdir(struct file * filp, void * dirent, filldir_t filldir)
len = strlen(name);
ino = pos->s_ino;
type = dt_type(pos);
filp->f_pos = ino;
filp->f_pos = pos->s_hash;
filp->private_data = sysfs_get(pos);

mutex_unlock(&sysfs_mutex);
Expand Down
9 changes: 4 additions & 5 deletions fs/sysfs/sysfs.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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 {
Expand Down Expand Up @@ -62,15 +61,15 @@ 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;
struct sysfs_dirent *removed_list;
} 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;
Expand Down

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