[PATCH] free_early_partial() should permit start == end

[PATCH] free_early_partial() should permit start == end

[Jan Beulich]

The per-CPU allocator, when using atom_size == PAGE_SIZE, may call
free_area_init_partial() this way.

Signed-off-by: Jan Beulich <jbeulich@novell.com>

---
 kernel/early_res.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- linux-2.6.34-rc2/kernel/early_res.c	2010-03-25 15:23:45.000000000 +0100
+++ 2.6.34-rc2-free_early_partial-zero-size/kernel/early_res.c	2010-03-26 14:49:41.000000000 +0100
@@ -335,10 +335,10 @@ void __init free_early_partial(u64 start
 
 try_next:
 	i = find_overlapped_early(start, end);
-	if (i >= max_early_res)
+	r = &early_res[i];
+	if (i >= max_early_res || !r->end)
 		return;
 
-	r = &early_res[i];
 	/* hole ? */
 	if (r->end >= end && r->start <= start) {
 		drop_range_partial(i, start, end);

Re: [PATCH] free_early_partial() should permit start == end

[Yinghai Lu]

On 03/26/2010 09:37 AM, Jan Beulich wrote:
> The per-CPU allocator, when using atom_size == PAGE_SIZE, may call
> free_area_init_partial() this way.
> 
> Signed-off-by: Jan Beulich <jbeulich@novell.com>
> 
> ---
>  kernel/early_res.c |    4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> --- linux-2.6.34-rc2/kernel/early_res.c	2010-03-25 15:23:45.000000000 +0100
> +++ 2.6.34-rc2-free_early_partial-zero-size/kernel/early_res.c	2010-03-26 14:49:41.000000000 +0100
> @@ -335,10 +335,10 @@ void __init free_early_partial(u64 start
>  
>  try_next:
>  	i = find_overlapped_early(start, end);
> -	if (i >= max_early_res)
> +	r = &early_res[i];
> +	if (i >= max_early_res || !r->end)
>  		return;
>  
> -	r = &early_res[i];
>  	/* hole ? */
>  	if (r->end >= end && r->start <= start) {
>  		drop_range_partial(i, start, end);
> 
> 

can you check if this patch work for you?

Thanks

Yinghai Lu

Subject: [PATCH -v6] x86: do not free zero sized per cpu areas
From: Ian Campbell <ian.campbell@citrix.com>

This avoids an infinite loop in free_early_partial().

Add a warning to free_early_partial to catch future problems.

-v5: put back start > end back into WARN_ONCE()
-v6: use one line for if according to linus

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Signed-off-by: Yinghai Lu <yinghai@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@elte.hu>
---
 kernel/early_res.c |    6 ++++++
 1 file changed, 6 insertions(+)

Index: linux-2.6/kernel/early_res.c
===================================================================
--- linux-2.6.orig/kernel/early_res.c
+++ linux-2.6/kernel/early_res.c
@@ -333,6 +333,12 @@ void __init free_early_partial(u64 start
 	struct early_res *r;
 	int i;
 
+	if (start == end)
+		return;
+
+	if (WARN_ONCE(start > end, "free_early_partial: wrong range [%#llx, %#llx]\n", start, end))
+		return;
+
 try_next:
 	i = find_overlapped_early(start, end);
 	if (i >= max_early_res)

Re: [PATCH] free_early_partial() should permit start == end

[Jan Beulich]

>>> Yinghai Lu <yinghai@kernel.org> 26.03.10 21:39 >>>
>can you check if this patch work for you?

I'm sure it works, too. But I find it less clean to add special case handling
instead of just getting the original code right.

Jan