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proc: use slower rb_first()

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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>
This commit is contained in:
Alexey Dobriyan
2018-04-10 16:32:20 -07:00
committed by Linus Torvalds
parent 05c3f29283
commit 4f1134370a
4 changed files with 17 additions and 19 deletions
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6
fs/proc/internal.h
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@@ -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;