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Commit 4f113437 authored by Alexey Dobriyan's avatar Alexey Dobriyan Committed by Linus Torvalds
Browse files

proc: use slower rb_first() 

In a typical for /proc "open+read+close" usecase, dentry is looked up
successfully on open only to be killed in dput() on close.  In fact
dentries which aren't /proc/*/...  and /proc/sys/* were almost NEVER
CACHED.  Simple printk in proc_lookup_de() shows that.

Now that ->delete hook intelligently picks which dentries should live in
dcache and which should not, rbtree caching is not necessary as dcache
does it job, at last!

As a side effect, struct proc_dir_entry shrinks by one pointer which can
go into inline name.

Link: http://lkml.kernel.org/r/20180314231032.GA15854@avx2


Signed-off-by: default avatarAlexey Dobriyan <adobriyan@gmail.com>
Acked-by: default avatarDavidlohr Bueso <dbueso@suse.de>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 05c3f292

fs/proc/generic.c

+12 −14
Original line number Diff line number Diff line
@@ -52,8 +52,8 @@ static int proc_match(const char *name, struct proc_dir_entry *de, unsigned int 


static struct proc_dir_entry *pde_subdir_first(struct proc_dir_entry *dir)

{

	return rb_entry_safe(rb_first_cached(&dir->subdir),

			     struct proc_dir_entry, subdir_node);

	return rb_entry_safe(rb_first(&dir->subdir), struct proc_dir_entry,

			     subdir_node);

}



static struct proc_dir_entry *pde_subdir_next(struct proc_dir_entry *dir)
@@ -66,7 +66,7 @@ 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_root.rb_node;

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



	while (node) {

		struct proc_dir_entry *de = rb_entry(node,
@@ -87,9 +87,8 @@ static struct proc_dir_entry *pde_subdir_find(struct proc_dir_entry *dir, 
static bool pde_subdir_insert(struct proc_dir_entry *dir,

			      struct proc_dir_entry *de)

{

	struct rb_root_cached *root = &dir->subdir;

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

	bool leftmost = true;

	struct rb_root *root = &dir->subdir;

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



	/* Figure out where to put new node */

	while (*new) {
@@ -101,16 +100,15 @@ static bool pde_subdir_insert(struct proc_dir_entry *dir, 
		parent = *new;

		if (result < 0)

			new = &(*new)->rb_left;

		else if (result > 0) {

		else if (result > 0)

			new = &(*new)->rb_right;

			leftmost = false;

		} else

		else

			return false;

	}



	/* Add new node and rebalance tree. */

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

	rb_insert_color_cached(&de->subdir_node, root, leftmost);

	rb_insert_color(&de->subdir_node, root);

	return true;

}
@@ -401,7 +399,7 @@ 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_CACHED;

	ent->subdir = RB_ROOT;

	refcount_set(&ent->refcnt, 1);

	spin_lock_init(&ent->pde_unload_lock);

	INIT_LIST_HEAD(&ent->pde_openers);
@@ -577,7 +575,7 @@ void remove_proc_entry(const char *name, struct proc_dir_entry *parent) 


	de = pde_subdir_find(parent, fn, len);

	if (de)

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

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

	write_unlock(&proc_subdir_lock);

	if (!de) {

		WARN(1, "name '%s'\n", name);
@@ -614,13 +612,13 @@ int remove_proc_subtree(const char *name, struct proc_dir_entry *parent) 
		write_unlock(&proc_subdir_lock);

		return -ENOENT;

	}

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

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



	de = root;

	while (1) {

		next = pde_subdir_first(de);

		if (next) {

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

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

			de = next;

			continue;

		}

fs/proc/internal.h

+3 −3
Original line number Diff line number Diff line
@@ -51,15 +51,15 @@ struct proc_dir_entry { 
	kgid_t gid;

	loff_t size;

	struct proc_dir_entry *parent;

	struct rb_root_cached subdir;

	struct rb_root subdir;

	struct rb_node subdir_node;

	char *name;

	umode_t mode;

	u8 namelen;

#ifdef CONFIG_64BIT

#define SIZEOF_PDE_INLINE_NAME	(192-147)

#define SIZEOF_PDE_INLINE_NAME	(192-139)

#else

#define SIZEOF_PDE_INLINE_NAME	(128-91)

#define SIZEOF_PDE_INLINE_NAME	(128-87)

#endif

	char inline_name[SIZEOF_PDE_INLINE_NAME];

} __randomize_layout;

fs/proc/proc_net.c

+1 −1
Original line number Diff line number Diff line
@@ -196,7 +196,7 @@ static __net_init int proc_net_ns_init(struct net *net) 
	if (!netd)

		goto out;



	netd->subdir = RB_ROOT_CACHED;

	netd->subdir = RB_ROOT;

	netd->data = net;

	netd->nlink = 2;

	netd->namelen = 3;

fs/proc/root.c

+1 −1
Original line number Diff line number Diff line
@@ -203,7 +203,7 @@ struct proc_dir_entry proc_root = { 
	.proc_iops	= &proc_root_inode_operations, 

	.proc_fops	= &proc_root_operations,

	.parent		= &proc_root,

	.subdir		= RB_ROOT_CACHED,

	.subdir		= RB_ROOT,

	.name		= proc_root.inline_name,

	.inline_name	= "/proc",

};