module: struct module_ref should contains long fields

module_ref contains two "unsigned int" fields.

Thats now too small, since some machines can open more than 2^32 files.

Check commit 518de9b39e8 (fs: allow for more than 2^31 files) for
reference.

We can add an aligned(2 * sizeof(unsigned long)) attribute to force
alloc_percpu() allocating module_ref areas in single cache lines.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
CC: Rusty Russell <rusty@rustcorp.com.au>
CC: Tejun Heo <tj@kernel.org>
CC: Robin Holt <holt@sgi.com>
CC: David Miller <davem@davemloft.net>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

1 files changed, 16 insertions, 5 deletions

diff --git a/include/linux/module.h b/include/linux/module.h
index 3cb7839a60b9..4598bf03e98b 100644
--- a/include/linux/module.h
+++ b/include/linux/module.h
@@ -205,6 +205,20 @@ enum module_state
         MODULE_STATE_GOING,
 };
 
+/**
+ * struct module_ref - per cpu module reference counts
+ * @incs: number of module get on this cpu
+ * @decs: number of module put on this cpu
+ *
+ * We force an alignment on 8 or 16 bytes, so that alloc_percpu()
+ * put @incs/@decs in same cache line, with no extra memory cost,
+ * since alloc_percpu() is fine grained.
+ */
+struct module_ref {
+        unsigned long incs;
+        unsigned long decs;
+} __attribute((aligned(2 * sizeof(unsigned long))));
+
 struct module
 {
         enum module_state state;
@@ -347,10 +361,7 @@ struct module
         /* Destruction function. */
         void (*exit)(void);
 
-        struct module_ref {
-                unsigned int incs;
-                unsigned int decs;
-        } __percpu *refptr;
+        struct module_ref __percpu *refptr;
 #endif
 
 #ifdef CONFIG_CONSTRUCTORS
@@ -434,7 +445,7 @@ extern void __module_put_and_exit(struct module *mod, long code)
 #define module_put_and_exit(code) __module_put_and_exit(THIS_MODULE, code);
 
 #ifdef CONFIG_MODULE_UNLOAD
-unsigned int module_refcount(struct module *mod);
+unsigned long module_refcount(struct module *mod);
 void __symbol_put(const char *symbol);
 #define symbol_put(x) __symbol_put(MODULE_SYMBOL_PREFIX #x)
 void symbol_put_addr(void *addr);