[PATCH] pgtables: fix GFP_KERNEL allocation with preempt disabled

[PATCH] pgtables: fix GFP_KERNEL allocation with preempt disabled

[Martin Hicks]

Hi Andrew,

This is a fix to the pgtable_quicklist code.  There is a GFP_KERNEL
allocation in pgtable_quicklist_alloc(), which spews the usual warnings
if the kernel is under heavy VM pressure and the reclaim code is
invoked.

This patch is against 2.6.12-rc2-mm2

Signed-off-by:  Martin Hicks <mort@sgi.com>


Index: linux-2.6.12-rc2.wk/include/asm-ia64/pgalloc.h
===================================================================
--- linux-2.6.12-rc2.wk.orig/include/asm-ia64/pgalloc.h	2005-04-19 09:01:06.000000000 -0700
+++ linux-2.6.12-rc2.wk/include/asm-ia64/pgalloc.h	2005-04-19 09:53:39.000000000 -0700
@@ -50,7 +50,7 @@ static inline void *pgtable_quicklist_al
 		ret[0] = 0;
 		--pgtable_quicklist_size;
 	} else {
-		ret = (unsigned long *)__get_free_page(GFP_KERNEL | __GFP_ZERO);
+		ret = (unsigned long *)__get_free_page(GFP_ATOMIC | __GFP_ZERO);
 	}
 
 	preempt_enable();

Re: [PATCH] pgtables: fix GFP_KERNEL allocation with preempt disabled

[David S. Miller]

On Tue, 19 Apr 2005 13:04:13 -0400
Martin Hicks <mort@sgi.com> wrote:

> This is a fix to the pgtable_quicklist code.  There is a GFP_KERNEL
> allocation in pgtable_quicklist_alloc(), which spews the usual warnings
> if the kernel is under heavy VM pressure and the reclaim code is
> invoked.
> 
> This patch is against 2.6.12-rc2-mm2

I think you should really drop the preempt disable during this allocation
instead, that's what we do in the sparc64 quicklist code.

It's very simple, change the code to:

		preempt_enable();
	} else {
		preempt_enable();
		ret = (unsigned long *) ...;
	}
	/* preempt_enable() no longer here */

Re: [PATCH] pgtables: fix GFP_KERNEL allocation with preempt disabled

[Martin Hicks]

On Tue, Apr 19, 2005 at 11:30:44AM -0700, David S. Miller wrote:
> 
> I think you should really drop the preempt disable during this allocation
> instead, that's what we do in the sparc64 quicklist code.
> 

Okay, here's an updated patch.

Hi Andrew,

This is a fix to the pgtable_quicklist code.  There is a GFP_KERNEL
allocation in pgtable_quicklist_alloc(), which spews the usual warnings
if the kernel is under heavy VM pressure and the reclaim code is
invoked.  re-enable preempt before we allocate the new page.

This patch is against 2.6.12-rc2-mm2

Signed-off-by:  Martin Hicks <mort@sgi.com>


 pgalloc.h |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

Index: linux-2.6.12-rc2.wk/include/asm-ia64/pgalloc.h
===================================================================
--- linux-2.6.12-rc2.wk.orig/include/asm-ia64/pgalloc.h	2005-04-19 10:13:16.000000000 -0700
+++ linux-2.6.12-rc2.wk/include/asm-ia64/pgalloc.h	2005-04-19 11:40:09.000000000 -0700
@@ -49,12 +49,12 @@ static inline void *pgtable_quicklist_al
 		pgtable_quicklist = (unsigned long *)(*ret);
 		ret[0] = 0;
 		--pgtable_quicklist_size;
+		preempt_enable();
 	} else {
+		preempt_enable();
 		ret = (unsigned long *)__get_free_page(GFP_KERNEL | __GFP_ZERO);
 	}
 
-	preempt_enable();
-
 	return ret;
 }
 

Re: [PATCH] pgtables: fix GFP_KERNEL allocation with preempt disabled

[David S. Miller]

On Tue, 19 Apr 2005 14:47:58 -0400
Martin Hicks <mort@wildopensource.com> wrote:

> Okay, here's an updated patch.

Looks great.