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Subject[PATCH 1/4] 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>
---
fs/sysfs/dir.c | 219 ++++++++++++++++++++++++++++-------------------------
fs/sysfs/sysfs.h | 9 +-
2 files changed, 120 insertions(+), 108 deletions(-)
diff --git a/fs/sysfs/dir.c b/fs/sysfs/dir.c
index 7fdf6a7..0daf255 100644
--- a/fs/sysfs/dir.c
+++ b/fs/sysfs/dir.c
@@ -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:
@@ -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);
}

/**
@@ -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",
@@ -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;
@@ -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",
@@ -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;
}

/**
@@ -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);
@@ -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;
}
@@ -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;
}
@@ -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);
diff --git a/fs/sysfs/sysfs.h b/fs/sysfs/sysfs.h
index ce29e28..545a8d4 100644
--- a/fs/sysfs/sysfs.h
+++ b/fs/sysfs/sysfs.h
@@ -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;
--
1.7.2.5


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