Re: [PATCH] [19/31] mm: export stable page flags

[Wu Fengguang]

On Wed, Dec 09, 2009 at 06:27:31AM +0800, Matt Mackall wrote:
> On Tue, 2009-12-08 at 22:16 +0100, Andi Kleen wrote:
> > From: Wu Fengguang <fengguang.wu@xxxxxxxxx>
> > 
> > Rename get_uflags() to stable_page_flags() and make it a global function
> > for use in the hwpoison page flags filter, which need to compare user
> > page flags with the value provided by user space.
> > 
> > Also move KPF_* to kernel-page-flags.h for use by user space tools.
> > 
> > CC: Matt Mackall <mpm@xxxxxxxxxxx>
> > CC: Nick Piggin <npiggin@xxxxxxx>
> > CC: Christoph Lameter <cl@xxxxxxxxxxxxxxxxxxxx>
> > CC: Andi Kleen <andi@xxxxxxxxxxxxxx>
> > Signed-off-by: Wu Fengguang <fengguang.wu@xxxxxxxxx>
> > Signed-off-by: Andi Kleen <ak@xxxxxxxxxxxxxxx>
> 
> Acked-by: Matt Mackall <mpm@xxxxxxxxxxx>

Andi and Matt,

Sorry the stable_page_flags() will be undefined on
!CONFIG_PROC_PAGE_MONITOR (it is almost always on,
except for some embedded systems).

Currently the easy solution is to add a Kconfig dependency to
CONFIG_PROC_PAGE_MONITOR.  When there comes more users (ie. some
ftrace event), we can then always compile in stable_page_flags().

Thanks,
Fengguang
---
 mm/Kconfig          |    1 +
 mm/memory-failure.c |    4 ++++
 2 files changed, 5 insertions(+)

--- linux-mm.orig/mm/Kconfig	2009-12-09 09:47:51.000000000 +0800
+++ linux-mm/mm/Kconfig	2009-12-09 09:58:54.000000000 +0800
@@ -259,6 +259,7 @@ config MEMORY_FAILURE
 config HWPOISON_INJECT
 	tristate "HWPoison pages injector"
 	depends on MEMORY_FAILURE && DEBUG_KERNEL
+	depends on PROC_PAGE_MONITOR
 
 config NOMMU_INITIAL_TRIM_EXCESS
 	int "Turn on mmap() excess space trimming before booting"
--- linux-mm.orig/mm/memory-failure.c	2009-12-09 09:49:13.000000000 +0800
+++ linux-mm/mm/memory-failure.c	2009-12-09 09:55:42.000000000 +0800
@@ -51,6 +51,7 @@ int sysctl_memory_failure_recovery __rea
 
 atomic_long_t mce_bad_pages __read_mostly = ATOMIC_LONG_INIT(0);
 
+#ifdef CONFIG_HWPOISON_INJECT
 u32 hwpoison_filter_enable = 1;
 u32 hwpoison_filter_dev_major = ~0U;
 u32 hwpoison_filter_dev_minor = ~0U;
@@ -160,6 +161,9 @@ int hwpoison_filter(struct page *p)
 	return 0;
 }
 EXPORT_SYMBOL_GPL(hwpoison_filter);
+#else
+int hwpoison_filter(struct page *p) { return 0; }
+#endif
 
 /*
  * Send all the processes who have the page mapped an ``action optional''
--
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