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procfs: use faster rb_first_cached()

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...  such that we can avoid the tree walks to get the node with the
smallest key.  Semantically the same, as the previously used rb_first(),
but O(1).  The main overhead is the extra footprint for the cached rb_node
pointer, which should not matter for procfs.

Link: http://lkml.kernel.org/r/20170719014603.19029-14-dave@stgolabs.net
Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Davidlohr Bueso 2017-09-08 16:15:15 -07:00 committed by Linus Torvalds
parent f2686bb486
commit 410bd5ecb2
4 changed files with 17 additions and 15 deletions
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26
fs/proc/generic.c
View File

@ -40,8 +40,8 @@ static int proc_match(unsigned int len, const char *name, struct proc_dir_entry
static struct proc_dir_entry *pde_subdir_first(struct proc_dir_entry *dir)
{
return rb_entry_safe(rb_first(&dir->subdir), struct proc_dir_entry,
subdir_node);
return rb_entry_safe(rb_first_cached(&dir->subdir),
struct proc_dir_entry, subdir_node);
}
static struct proc_dir_entry *pde_subdir_next(struct proc_dir_entry *dir)
@ -54,7 +54,7 @@ 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_node;
struct rb_node *node = dir->subdir.rb_root.rb_node;
while (node) {
struct proc_dir_entry *de = rb_entry(node,
@ -75,8 +75,9 @@ 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 *root = &dir->subdir;
struct rb_node **new = &root->rb_node, *parent = NULL;
struct rb_root_cached *root = &dir->subdir;
struct rb_node **new = &root->rb_root.rb_node, *parent = NULL;
bool leftmost = true;
/* Figure out where to put new node */
while (*new) {
@ -88,15 +89,16 @@ 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;
else
leftmost = false;
} else
return false;
}
/* Add new node and rebalance tree. */
rb_link_node(&de->subdir_node, parent, new);
rb_insert_color(&de->subdir_node, root);
rb_insert_color_cached(&de->subdir_node, root, leftmost);
return true;
}
@ -369,7 +371,7 @@ 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;
ent->subdir = RB_ROOT_CACHED;
atomic_set(&ent->count, 1);
spin_lock_init(&ent->pde_unload_lock);
INIT_LIST_HEAD(&ent->pde_openers);
@ -553,7 +555,7 @@ void remove_proc_entry(const char *name, struct proc_dir_entry *parent)
de = pde_subdir_find(parent, fn, len);
if (de)
rb_erase(&de->subdir_node, &parent->subdir);
rb_erase_cached(&de->subdir_node, &parent->subdir);
write_unlock(&proc_subdir_lock);
if (!de) {
WARN(1, "name '%s'\n", name);
@ -590,13 +592,13 @@ int remove_proc_subtree(const char *name, struct proc_dir_entry *parent)
write_unlock(&proc_subdir_lock);
return -ENOENT;
}
rb_erase(&root->subdir_node, &parent->subdir);
rb_erase_cached(&root->subdir_node, &parent->subdir);
de = root;
while (1) {
next = pde_subdir_first(de);
if (next) {
rb_erase(&next->subdir_node, &de->subdir);
rb_erase_cached(&next->subdir_node, &de->subdir);
de = next;
continue;
}

2
fs/proc/internal.h
View File

@ -40,7 +40,7 @@ struct proc_dir_entry {
const struct inode_operations *proc_iops;
const struct file_operations *proc_fops;
struct proc_dir_entry *parent;
struct rb_root subdir;
struct rb_root_cached subdir;
struct rb_node subdir_node;
void *data;
atomic_t count; /* use count */

2
fs/proc/proc_net.c
View File

@ -196,7 +196,7 @@ static __net_init int proc_net_ns_init(struct net *net)
if (!netd)
goto out;
netd->subdir = RB_ROOT;
netd->subdir = RB_ROOT_CACHED;
netd->data = net;
netd->nlink = 2;
netd->namelen = 3;

2
fs/proc/root.c
View File

@ -210,7 +210,7 @@ struct proc_dir_entry proc_root = {
.proc_iops = &proc_root_inode_operations,
.proc_fops = &proc_root_operations,
.parent = &proc_root,
.subdir = RB_ROOT,
.subdir = RB_ROOT_CACHED,
.name = "/proc",
};