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: Alexey Dobriyan <adobriyan@gmail.com>
Acked-by: Davidlohr Bueso <dbueso@suse.de>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

4 files changed, 17 insertions, 19 deletions

diff --git a/fs/proc/generic.c b/fs/proc/generic.c
index fc0333fd5676..04c4804cbdef 100644
--- a/fs/proc/generic.c
+++ b/fs/proc/generic.c
@@ -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;
                 }
diff --git a/fs/proc/internal.h b/fs/proc/internal.h
index b7024f174778..0f1692e63cb6 100644
--- a/fs/proc/internal.h
+++ b/fs/proc/internal.h
@@ -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;
diff --git a/fs/proc/proc_net.c b/fs/proc/proc_net.c
index e5fe3d400737..1763f370489d 100644
--- 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_CACHED;
+        netd->subdir = RB_ROOT;
         netd->data = net;
         netd->nlink = 2;
         netd->namelen = 3;
diff --git a/fs/proc/root.c b/fs/proc/root.c
index 76c996457ff9..61b7340b357a 100644
--- a/fs/proc/root.c
+++ b/fs/proc/root.c
@@ -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",
 };