2009-03-27 09:35:03

by Metzger, Markus T

Subject: [patch 2/14] x86, mm: add release_locked_buffer_on_behalf

Allow the release of a locked buffer on behalf of another task.


Signed-off-by: Markus Metzger <[email protected]>
---

Index: git-tip/include/linux/mm.h
===================================================================
--- git-tip.orig/include/linux/mm.h 2009-03-23 16:23:19.000000000 +0100
+++ git-tip/include/linux/mm.h 2009-03-23 16:33:03.000000000 +0100
@@ -13,6 +13,7 @@
#include <linux/prio_tree.h>
#include <linux/debug_locks.h>
#include <linux/mm_types.h>
+#include <linux/sched.h>

struct mempolicy;
struct anon_vma;
@@ -1318,6 +1319,11 @@ void vmemmap_populate_print_last(void);

extern void *alloc_locked_buffer(size_t size);
extern void free_locked_buffer(void *buffer, size_t size);
-extern void release_locked_buffer(void *buffer, size_t size);
+extern void release_locked_buffer_on_behalf(struct mm_struct *mm,
+ void *buffer, size_t size);
+static inline void release_locked_buffer(void *buffer, size_t size)
+{
+ release_locked_buffer_on_behalf(current->mm, buffer, size);
+}
#endif /* __KERNEL__ */
#endif /* _LINUX_MM_H */
Index: git-tip/mm/mlock.c
===================================================================
--- git-tip.orig/mm/mlock.c 2009-03-23 16:23:19.000000000 +0100
+++ git-tip/mm/mlock.c 2009-03-23 16:24:24.000000000 +0100
@@ -660,16 +660,17 @@ void *alloc_locked_buffer(size_t size)
return buffer;
}

-void release_locked_buffer(void *buffer, size_t size)
+void release_locked_buffer_on_behalf(struct mm_struct *mm,
+ void *buffer, size_t size)
{
unsigned long pgsz = PAGE_ALIGN(size) >> PAGE_SHIFT;

- down_write(&current->mm->mmap_sem);
+ down_write(&mm->mmap_sem);

- current->mm->total_vm -= pgsz;
- current->mm->locked_vm -= pgsz;
+ mm->total_vm -= pgsz;
+ mm->locked_vm -= pgsz;

- up_write(&current->mm->mmap_sem);
+ up_write(&mm->mmap_sem);
}

void free_locked_buffer(void *buffer, size_t size)
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2009-03-27 14:25:58

by Oleg Nesterov

Subject: Re: [patch 2/14] x86, mm: add release_locked_buffer_on_behalf

On 03/27, Markus Metzger wrote:
>
> -void release_locked_buffer(void *buffer, size_t size)
> +void release_locked_buffer_on_behalf(struct mm_struct *mm,
> + void *buffer, size_t size)
> {
> unsigned long pgsz = PAGE_ALIGN(size) >> PAGE_SHIFT;
>
> - down_write(&current->mm->mmap_sem);
> + down_write(&mm->mmap_sem);
>
> - current->mm->total_vm -= pgsz;
> - current->mm->locked_vm -= pgsz;
> + mm->total_vm -= pgsz;
> + mm->locked_vm -= pgsz;
>
> - up_write(&current->mm->mmap_sem);
> + up_write(&mm->mmap_sem);
> }

If you change this helper, perhaps you can remove the "void *buffer"
argument? It is not used. Actually, this helper should be renamed.
It doesn't free the memory, it only updates mm->xxx_vm.

Oleg.

2009-03-27 15:19:50

by Metzger, Markus T

Subject: RE: [patch 2/14] x86, mm: add release_locked_buffer_on_behalf

>-----Original Message-----
>From: Oleg Nesterov [mailto:[email protected]]
>Sent: Friday, March 27, 2009 3:22 PM
>To: Metzger, Markus T
>Cc: [email protected]; [email protected]; [email protected]; [email protected];
>[email protected]; [email protected]; [email protected]; Villacis, Juan;
>[email protected]
>Subject: Re: [patch 2/14] x86, mm: add release_locked_buffer_on_behalf
>
>On 03/27, Markus Metzger wrote:
>>
>> -void release_locked_buffer(void *buffer, size_t size)
>> +void release_locked_buffer_on_behalf(struct mm_struct *mm,
>> + void *buffer, size_t size)
>> {
>> unsigned long pgsz = PAGE_ALIGN(size) >> PAGE_SHIFT;
>>
>> - down_write(&current->mm->mmap_sem);
>> + down_write(&mm->mmap_sem);
>>
>> - current->mm->total_vm -= pgsz;
>> - current->mm->locked_vm -= pgsz;
>> + mm->total_vm -= pgsz;
>> + mm->locked_vm -= pgsz;
>>
>> - up_write(&current->mm->mmap_sem);
>> + up_write(&mm->mmap_sem);
>> }
>
>If you change this helper, perhaps you can remove the "void *buffer"
>argument? It is not used. Actually, this helper should be renamed.
>It doesn't free the memory, it only updates mm->xxx_vm.

OK.

There's an alloc/free pair. This one is in between to allow another task to free
the buffer and get the memory correctly refunded.

How about refund_locked_buffer_memory(struct mm_struct *, size_t)?

regards,
markus.

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85622 Feldkirchen/Muenchen Germany
Sitz der Gesellschaft: Feldkirchen bei Muenchen
Geschaeftsfuehrer: Douglas Lusk, Peter Gleissner, Hannes Schwaderer
Registergericht: Muenchen HRB 47456 Ust.-IdNr.
VAT Registration No.: DE129385895
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the sole use of the intended recipient(s). Any review or distribution
by others is strictly prohibited. If you are not the intended
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