page flags: prioritize kasan bits over last-cpuid

Message ID 20190307075124.3424302-1-arnd@arndb.de
State New
Headers show
Series
  • page flags: prioritize kasan bits over last-cpuid
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Commit Message

Arnd Bergmann March 7, 2019, 7:51 a.m.
ARM64 randdconfig builds regularly run into a build error, especially
when NUMA_BALANCING and SPARSEMEM are enabled but not SPARSEMEM_VMEMMAP:

 #error "KASAN: not enough bits in page flags for tag"

The last-cpuid bits are already contitional on the available space,
so the result of the calculation is a bit random on whether they
were already left out or not.

Adding the kasan tag bits before last-cpuid makes it much more likely
to end up with a successful build here, and should be reliable for
randconfig at least, as long as that does not randomize NR_CPUS
or NODES_SHIFT but uses the defaults.

Fixes: 2813b9c02962 ("kasan, mm, arm64: tag non slab memory allocated via pagealloc")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

---
 include/linux/page-flags-layout.h | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

-- 
2.20.0

Comments

Andrey Konovalov March 7, 2019, 2:15 p.m. | #1
On Thu, Mar 7, 2019 at 8:51 AM Arnd Bergmann <arnd@arndb.de> wrote:
>

> ARM64 randdconfig builds regularly run into a build error, especially

> when NUMA_BALANCING and SPARSEMEM are enabled but not SPARSEMEM_VMEMMAP:

>

>  #error "KASAN: not enough bits in page flags for tag"

>

> The last-cpuid bits are already contitional on the available space,

> so the result of the calculation is a bit random on whether they

> were already left out or not.

>

> Adding the kasan tag bits before last-cpuid makes it much more likely

> to end up with a successful build here, and should be reliable for

> randconfig at least, as long as that does not randomize NR_CPUS

> or NODES_SHIFT but uses the defaults.

>

> Fixes: 2813b9c02962 ("kasan, mm, arm64: tag non slab memory allocated via pagealloc")

> Signed-off-by: Arnd Bergmann <arnd@arndb.de>

> ---

>  include/linux/page-flags-layout.h | 14 ++++++++------

>  1 file changed, 8 insertions(+), 6 deletions(-)

>

> diff --git a/include/linux/page-flags-layout.h b/include/linux/page-flags-layout.h

> index 1dda31825ec4..9bc0751e68b2 100644

> --- a/include/linux/page-flags-layout.h

> +++ b/include/linux/page-flags-layout.h

> @@ -76,21 +76,23 @@

>  #define LAST_CPUPID_SHIFT 0

>  #endif

>

> -#if SECTIONS_WIDTH+ZONES_WIDTH+NODES_SHIFT+LAST_CPUPID_SHIFT <= BITS_PER_LONG - NR_PAGEFLAGS

> +#ifdef CONFIG_KASAN_SW_TAGS

> +#define KASAN_TAG_WIDTH 8

> +#else

> +#define KASAN_TAG_WIDTH 0

> +#endif

> +

> +#if SECTIONS_WIDTH+ZONES_WIDTH+NODES_SHIFT+LAST_CPUPID_SHIFT+KASAN_TAG_WIDTH \

> +       <= BITS_PER_LONG - NR_PAGEFLAGS

>  #define LAST_CPUPID_WIDTH LAST_CPUPID_SHIFT

>  #else

>  #define LAST_CPUPID_WIDTH 0

>  #endif

>

> -#ifdef CONFIG_KASAN_SW_TAGS

> -#define KASAN_TAG_WIDTH 8

>  #if SECTIONS_WIDTH+NODES_WIDTH+ZONES_WIDTH+LAST_CPUPID_WIDTH+KASAN_TAG_WIDTH \

>         > BITS_PER_LONG - NR_PAGEFLAGS

>  #error "KASAN: not enough bits in page flags for tag"

>  #endif

> -#else

> -#define KASAN_TAG_WIDTH 0

> -#endif

>

>  /*

>   * We are going to use the flags for the page to node mapping if its in

> --

> 2.20.0

>


Reviewed-by: Andrey Konovalov <andreyknvl@google.com>


Thanks!

Patch

diff --git a/include/linux/page-flags-layout.h b/include/linux/page-flags-layout.h
index 1dda31825ec4..9bc0751e68b2 100644
--- a/include/linux/page-flags-layout.h
+++ b/include/linux/page-flags-layout.h
@@ -76,21 +76,23 @@ 
 #define LAST_CPUPID_SHIFT 0
 #endif
 
-#if SECTIONS_WIDTH+ZONES_WIDTH+NODES_SHIFT+LAST_CPUPID_SHIFT <= BITS_PER_LONG - NR_PAGEFLAGS
+#ifdef CONFIG_KASAN_SW_TAGS
+#define KASAN_TAG_WIDTH 8
+#else
+#define KASAN_TAG_WIDTH 0
+#endif
+
+#if SECTIONS_WIDTH+ZONES_WIDTH+NODES_SHIFT+LAST_CPUPID_SHIFT+KASAN_TAG_WIDTH \
+	<= BITS_PER_LONG - NR_PAGEFLAGS
 #define LAST_CPUPID_WIDTH LAST_CPUPID_SHIFT
 #else
 #define LAST_CPUPID_WIDTH 0
 #endif
 
-#ifdef CONFIG_KASAN_SW_TAGS
-#define KASAN_TAG_WIDTH 8
 #if SECTIONS_WIDTH+NODES_WIDTH+ZONES_WIDTH+LAST_CPUPID_WIDTH+KASAN_TAG_WIDTH \
 	> BITS_PER_LONG - NR_PAGEFLAGS
 #error "KASAN: not enough bits in page flags for tag"
 #endif
-#else
-#define KASAN_TAG_WIDTH 0
-#endif
 
 /*
  * We are going to use the flags for the page to node mapping if its in