proc: move "struct proc_dir_entry" into kmem cache
"struct proc_dir_entry" is variable sized because of 0-length trailing
array for name, however, because of SLAB padding allocations it is
possible to make "struct proc_dir_entry" fixed sized and allocate same
amount of memory.
It buys fine-grained debugging with poisoning and usercopy protection
which is not possible with kmalloc-* caches.
Currently, on 32-bit 91+ byte allocations go into kmalloc-128 and on
64-bit 147+ byte allocations go to kmalloc-192 anyway.
Additional memory is allocated only for 38/46+ byte long names which are
rare or may not even exist in the wild.
Link: http://lkml.kernel.org/r/20180223205504.GA17139@avx2
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/fs/proc/internal.h b/fs/proc/internal.h
index dc00ef8..0ead007 100644
--- a/fs/proc/internal.h
+++ b/fs/proc/internal.h
@@ -52,11 +52,20 @@ struct proc_dir_entry {
struct proc_dir_entry *parent;
struct rb_root_cached subdir;
struct rb_node subdir_node;
+ char *name;
umode_t mode;
u8 namelen;
- char name[];
+#ifdef CONFIG_64BIT
+#define SIZEOF_PDE_INLINE_NAME (192-147)
+#else
+#define SIZEOF_PDE_INLINE_NAME (128-91)
+#endif
+ char inline_name[SIZEOF_PDE_INLINE_NAME];
} __randomize_layout;
+extern struct kmem_cache *proc_dir_entry_cache;
+void pde_free(struct proc_dir_entry *pde);
+
union proc_op {
int (*proc_get_link)(struct dentry *, struct path *);
int (*proc_show)(struct seq_file *m,