Commit 710585d4 authored by Nicolas Dichtel's avatar Nicolas Dichtel Committed by Linus Torvalds
Browse files

fs/proc: use a rb tree for the directory entries 



When a lot of netdevices are created, one of the bottleneck is the
creation of proc entries.  This serie aims to accelerate this part.

The current implementation for the directories in /proc is using a single
linked list.  This is slow when handling directories with large numbers of
entries (eg netdevice-related entries when lots of tunnels are opened).

This patch replaces this linked list by a red-black tree.

Here are some numbers:

dummy30000.batch contains 30 000 times 'link add type dummy'.

Before the patch:
  $ time ip -b dummy30000.batch
  real    2m31.950s
  user    0m0.440s
  sys     2m21.440s
  $ time rmmod dummy
  real    1m35.764s
  user    0m0.000s
  sys     1m24.088s

After the patch:
  $ time ip -b dummy30000.batch
  real    2m0.874s
  user    0m0.448s
  sys     1m49.720s
  $ time rmmod dummy
  real    1m13.988s
  user    0m0.000s
  sys     1m1.008s

The idea of improving this part was suggested by Thierry Herbelot.

[akpm@linux-foundation.org: initialise proc_root.subdir at compile time]
Signed-off-by: default avatarNicolas Dichtel <nicolas.dichtel@6wind.com>
Acked-by: default avatarDavid S. Miller <davem@davemloft.net>
Cc: Thierry Herbelot <thierry.herbelot@6wind.com>.
Acked-by: default avatar"Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 9edad6ea

fs/proc/generic.c

+105 −59
Original line number Diff line number Diff line
@@ -31,9 +31,81 @@ static DEFINE_SPINLOCK(proc_subdir_lock); 


static int proc_match(unsigned int len, const char *name, struct proc_dir_entry *de)

{

	if (de->namelen != len)

		return 0;

	return !memcmp(name, de->name, len);

	if (len < de->namelen)

		return -1;

	if (len > de->namelen)

		return 1;



	return memcmp(name, de->name, len);

}



static struct proc_dir_entry *pde_subdir_first(struct proc_dir_entry *dir)

{

	struct rb_node *node = rb_first(&dir->subdir);



	if (node == NULL)

		return NULL;



	return rb_entry(node, struct proc_dir_entry, subdir_node);

}



static struct proc_dir_entry *pde_subdir_next(struct proc_dir_entry *dir)

{

	struct rb_node *node = rb_next(&dir->subdir_node);



	if (node == NULL)

		return NULL;



	return rb_entry(node, struct proc_dir_entry, subdir_node);

}



static struct proc_dir_entry *pde_subdir_find(struct proc_dir_entry *dir,

					      const char *name,

					      unsigned int len)

{

	struct rb_node *node = dir->subdir.rb_node;



	while (node) {

		struct proc_dir_entry *de = container_of(node,

							 struct proc_dir_entry,

							 subdir_node);

		int result = proc_match(len, name, de);



		if (result < 0)

			node = node->rb_left;

		else if (result > 0)

			node = node->rb_right;

		else

			return de;

	}

	return NULL;

}



static bool pde_subdir_insert(struct proc_dir_entry *dir,

			      struct proc_dir_entry *de)

{

	struct rb_root *root = &dir->subdir;

	struct rb_node **new = &root->rb_node, *parent = NULL;



	/* Figure out where to put new node */

	while (*new) {

		struct proc_dir_entry *this =

			container_of(*new, struct proc_dir_entry, subdir_node);

		int result = proc_match(de->namelen, de->name, this);



		parent = *new;

		if (result < 0)

			new = &(*new)->rb_left;

		else if (result > 0)

			new = &(*new)->rb_right;

		else

			return false;

	}



	/* Add new node and rebalance tree. */

	rb_link_node(&de->subdir_node, parent, new);

	rb_insert_color(&de->subdir_node, root);

	return true;

}



static int proc_notify_change(struct dentry *dentry, struct iattr *iattr)
@@ -92,10 +164,7 @@ static int __xlate_proc_name(const char *name, struct proc_dir_entry **ret, 
			break;



		len = next - cp;

		for (de = de->subdir; de ; de = de->next) {

			if (proc_match(len, cp, de))

				break;

		}

		de = pde_subdir_find(de, cp, len);

		if (!de) {

			WARN(1, "name '%s'\n", name);

			return -ENOENT;
@@ -183,10 +252,8 @@ struct dentry *proc_lookup_de(struct proc_dir_entry *de, struct inode *dir, 
	struct inode *inode;



	spin_lock(&proc_subdir_lock);

	for (de = de->subdir; de ; de = de->next) {

		if (de->namelen != dentry->d_name.len)

			continue;

		if (!memcmp(dentry->d_name.name, de->name, de->namelen)) {

	de = pde_subdir_find(de, dentry->d_name.name, dentry->d_name.len);

	if (de) {

		pde_get(de);

		spin_unlock(&proc_subdir_lock);

		inode = proc_get_inode(dir->i_sb, de);
@@ -196,7 +263,6 @@ struct dentry *proc_lookup_de(struct proc_dir_entry *de, struct inode *dir, 
		d_add(dentry, inode);

		return NULL;

	}

	}

	spin_unlock(&proc_subdir_lock);

	return ERR_PTR(-ENOENT);

}
@@ -225,7 +291,7 @@ int proc_readdir_de(struct proc_dir_entry *de, struct file *file, 
		return 0;



	spin_lock(&proc_subdir_lock);

	de = de->subdir;

	de = pde_subdir_first(de);

	i = ctx->pos - 2;

	for (;;) {

		if (!de) {
@@ -234,7 +300,7 @@ int proc_readdir_de(struct proc_dir_entry *de, struct file *file, 
		}

		if (!i)

			break;

		de = de->next;

		de = pde_subdir_next(de);

		i--;

	}
@@ -249,7 +315,7 @@ int proc_readdir_de(struct proc_dir_entry *de, struct file *file, 
		}

		spin_lock(&proc_subdir_lock);

		ctx->pos++;

		next = de->next;

		next = pde_subdir_next(de);

		pde_put(de);

		de = next;

	} while (de);
@@ -286,7 +352,6 @@ static const struct inode_operations proc_dir_inode_operations = { 


static int proc_register(struct proc_dir_entry * dir, struct proc_dir_entry * dp)

{

	struct proc_dir_entry *tmp;

	int ret;



	ret = proc_alloc_inum(&dp->low_ino);
@@ -308,17 +373,10 @@ static int proc_register(struct proc_dir_entry * dir, struct proc_dir_entry * dp 
	}



	spin_lock(&proc_subdir_lock);



	for (tmp = dir->subdir; tmp; tmp = tmp->next)

		if (strcmp(tmp->name, dp->name) == 0) {

	dp->parent = dir;

	if (pde_subdir_insert(dir, dp) == false)

		WARN(1, "proc_dir_entry '%s/%s' already registered\n",

		     dir->name, dp->name);

			break;

		}



	dp->next = dir->subdir;

	dp->parent = dir;

	dir->subdir = dp;

	spin_unlock(&proc_subdir_lock);



	return 0;
@@ -354,6 +412,7 @@ static struct proc_dir_entry *__proc_create(struct proc_dir_entry **parent, 
	ent->namelen = qstr.len;

	ent->mode = mode;

	ent->nlink = nlink;

	ent->subdir = RB_ROOT;

	atomic_set(&ent->count, 1);

	spin_lock_init(&ent->pde_unload_lock);

	INIT_LIST_HEAD(&ent->pde_openers);
@@ -485,7 +544,6 @@ void pde_put(struct proc_dir_entry *pde) 
 */

void remove_proc_entry(const char *name, struct proc_dir_entry *parent)

{

	struct proc_dir_entry **p;

	struct proc_dir_entry *de = NULL;

	const char *fn = name;

	unsigned int len;
@@ -497,14 +555,9 @@ void remove_proc_entry(const char *name, struct proc_dir_entry *parent) 
	}

	len = strlen(fn);



	for (p = &parent->subdir; *p; p=&(*p)->next ) {

		if (proc_match(len, fn, *p)) {

			de = *p;

			*p = de->next;

			de->next = NULL;

			break;

		}

	}

	de = pde_subdir_find(parent, fn, len);

	if (de)

		rb_erase(&de->subdir_node, &parent->subdir);

	spin_unlock(&proc_subdir_lock);

	if (!de) {

		WARN(1, "name '%s'\n", name);
@@ -516,16 +569,15 @@ void remove_proc_entry(const char *name, struct proc_dir_entry *parent) 
	if (S_ISDIR(de->mode))

		parent->nlink--;

	de->nlink = 0;

	WARN(de->subdir, "%s: removing non-empty directory "

			 "'%s/%s', leaking at least '%s'\n", __func__,

			 de->parent->name, de->name, de->subdir->name);

	WARN(pde_subdir_first(de),

	     "%s: removing non-empty directory '%s/%s', leaking at least '%s'\n",

	     __func__, de->parent->name, de->name, pde_subdir_first(de)->name);

	pde_put(de);

}

EXPORT_SYMBOL(remove_proc_entry);



int remove_proc_subtree(const char *name, struct proc_dir_entry *parent)

{

	struct proc_dir_entry **p;

	struct proc_dir_entry *root = NULL, *de, *next;

	const char *fn = name;

	unsigned int len;
@@ -537,24 +589,18 @@ int remove_proc_subtree(const char *name, struct proc_dir_entry *parent) 
	}

	len = strlen(fn);



	for (p = &parent->subdir; *p; p=&(*p)->next ) {

		if (proc_match(len, fn, *p)) {

			root = *p;

			*p = root->next;

			root->next = NULL;

			break;

		}

	}

	root = pde_subdir_find(parent, fn, len);

	if (!root) {

		spin_unlock(&proc_subdir_lock);

		return -ENOENT;

	}

	rb_erase(&root->subdir_node, &parent->subdir);



	de = root;

	while (1) {

		next = de->subdir;

		next = pde_subdir_first(de);

		if (next) {

			de->subdir = next->next;

			next->next = NULL;

			rb_erase(&next->subdir_node, &de->subdir);

			de = next;

			continue;

		}

fs/proc/internal.h

+6 −5
Original line number Diff line number Diff line
@@ -24,10 +24,9 @@ struct mempolicy; 
 * tree) of these proc_dir_entries, so that we can dynamically

 * add new files to /proc.

 *

 * The "next" pointer creates a linked list of one /proc directory,

 * while parent/subdir create the directory structure (every

 * /proc file has a parent, but "subdir" is NULL for all

 * non-directory entries).

 * parent/subdir are used for the directory structure (every /proc file has a

 * parent, but "subdir" is empty for all non-directory entries).

 * subdir_node is used to build the rb tree "subdir" of the parent.

 */

struct proc_dir_entry {

	unsigned int low_ino;
@@ -38,7 +37,9 @@ struct proc_dir_entry { 
	loff_t size;

	const struct inode_operations *proc_iops;

	const struct file_operations *proc_fops;

	struct proc_dir_entry *next, *parent, *subdir;

	struct proc_dir_entry *parent;

	struct rb_root subdir;

	struct rb_node subdir_node;

	void *data;

	atomic_t count;		/* use count */

	atomic_t in_use;	/* number of callers into module in progress; */

fs/proc/proc_net.c

+1 −0
Original line number Diff line number Diff line
@@ -192,6 +192,7 @@ static __net_init int proc_net_ns_init(struct net *net) 
	if (!netd)

		goto out;



	netd->subdir = RB_ROOT;

	netd->data = net;

	netd->nlink = 2;

	netd->namelen = 3;

fs/proc/root.c

+1 −0
Original line number Diff line number Diff line
@@ -251,6 +251,7 @@ struct proc_dir_entry proc_root = { 
	.proc_iops	= &proc_root_inode_operations, 

	.proc_fops	= &proc_root_operations,

	.parent		= &proc_root,

	.subdir		= RB_ROOT,

	.name		= "/proc",

};

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