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 <[email protected]>
Acked-by: Davidlohr Bueso <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Al Viro <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

1 files changed, 3 insertions, 3 deletions

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;