x86/mm/mtrr: Mark the 'range_new' static variable in mtrr_calc_range_state() as __ini...

'range_new' doesn't seem to be used after init. It is only passed
to memset(), sum_ranges(), memcmp() and x86_get_mtrr_mem_range(), the
latter of which also only passes it on to various *range*
library functions.

So mark it __initdata to free up an extra page after init.

Its contents are wiped at every call to mtrr_calc_range_state(),
so it being static is not about preserving state between calls,
but simply to avoid a 4k+ stack frame. While there, add a
comment explaining this and why it's safe.

We could also mark nr_range_new as __initdata, but since it's
just a single int and also doesn't carry state between calls (it
is unconditionally assigned to before it is read), we might as
well make it an ordinary automatic variable.

Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Toshi Kani <toshi.kani@hp.com>
Link: http://lkml.kernel.org/r/1449002691-20783-1-git-send-email-linux@rasmusvillemoes.dk
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/arch/x86/kernel/cpu/mtrr/cleanup.c b/arch/x86/kernel/cpu/mtrr/cleanup.c
index 70d7c93f455083e8703f6a37e94dc636432d7b64..0d98503c2245aab81283526c062f746650b99c32 100644 (file)
--- a/arch/x86/kernel/cpu/mtrr/cleanup.c
+++ b/arch/x86/kernel/cpu/mtrr/cleanup.c
@@ -593,9 +593,16 @@ mtrr_calc_range_state(u64 chunk_size, u64 gran_size,
                      unsigned long x_remove_base,
                      unsigned long x_remove_size, int i)
 {
-       static struct range range_new[RANGE_NUM];
+       /*
+        * range_new should really be an automatic variable, but
+        * putting 4096 bytes on the stack is frowned upon, to put it
+        * mildly. It is safe to make it a static __initdata variable,
+        * since mtrr_calc_range_state is only called during init and
+        * there's no way it will call itself recursively.
+        */
+       static struct range range_new[RANGE_NUM] __initdata;
        unsigned long range_sums_new;
-       static int nr_range_new;
+       int nr_range_new;
        int num_reg;
 
        /* Convert ranges to var ranges state: */