procfs: use faster rb_first_cached()

...  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>

diff --git a/fs/proc/generic.c b/fs/proc/generic.c
index 85566abe6f83a5fd7a9a83d3f79ffb9a1cfddf85..793a6757466860e6b8c34f2559f8186c0756239e 100644 (file)
--- a/fs/proc/generic.c
+++ b/fs/proc/generic.c
@@ -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;
                }

diff --git a/fs/proc/internal.h b/fs/proc/internal.h
index 2cbfcd32e884478c9806c64986874bf49bd8ed8e..a34195e92b206c9f2cd44ee4a627f53efedc3fd8 100644 (file)
--- a/fs/proc/internal.h
+++ b/fs/proc/internal.h
@@ -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 */

diff --git a/fs/proc/proc_net.c b/fs/proc/proc_net.c
index d72fc40241d9c6897df7656a95402d0a39511bfd..a2bf369c923dcf1c3b788fcd16320bbc425fc1fd 100644 (file)
--- a/fs/proc/proc_net.c
+++ b/fs/proc/proc_net.c
@@ -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;

diff --git a/fs/proc/root.c b/fs/proc/root.c
index deecb397daa30d769f6750f11dcc7cbbfec805fb..926fb27f4ca26cb27c17c2a3d9eed9b9e32fc639 100644 (file)
--- a/fs/proc/root.c
+++ b/fs/proc/root.c
@@ -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",
 };