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>

3 files changed, 21 insertions, 10 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);
diff --git a/kernel/debug/kdb/kdb_main.c b/kernel/debug/kdb/kdb_main.c
index 63786e71a3cd..e2ae7349437f 100644
--- a/kernel/debug/kdb/kdb_main.c
+++ b/kernel/debug/kdb/kdb_main.c
@@ -1982,7 +1982,7 @@ static int kdb_lsmod(int argc, const char **argv)
                 kdb_printf("%-20s%8u  0x%p ", mod->name,
                            mod->core_size, (void *)mod);
 #ifdef CONFIG_MODULE_UNLOAD
-                kdb_printf("%4d ", module_refcount(mod));
+                kdb_printf("%4ld ", module_refcount(mod));
 #endif
                 if (mod->state == MODULE_STATE_GOING)
                         kdb_printf(" (Unloading)");
diff --git a/kernel/module.c b/kernel/module.c
index 4928cffc3dcc..14b8e82e05d4 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -725,9 +725,9 @@ static int try_stop_module(struct module *mod, int flags, int *forced)
         }
 }
 
-unsigned int module_refcount(struct module *mod)
+unsigned long module_refcount(struct module *mod)
 {
-        unsigned int incs = 0, decs = 0;
+        unsigned long incs = 0, decs = 0;
         int cpu;
 
         for_each_possible_cpu(cpu)
@@ -853,7 +853,7 @@ static inline void print_unload_info(struct seq_file *m, struct module *mod)
         struct module_use *use;
         int printed_something = 0;
 
-        seq_printf(m, " %u ", module_refcount(mod));
+        seq_printf(m, " %lu ", module_refcount(mod));
 
         /* Always include a trailing , so userspace can differentiate
            between this and the old multi-field proc format. */
@@ -903,7 +903,7 @@ EXPORT_SYMBOL_GPL(symbol_put_addr);
 static ssize_t show_refcnt(struct module_attribute *mattr,
                            struct module_kobject *mk, char *buffer)
 {
-        return sprintf(buffer, "%u\n", module_refcount(mk->mod));
+        return sprintf(buffer, "%lu\n", module_refcount(mk->mod));
 }
 
 static struct module_attribute refcnt = {