2009-03-31 13:03:42

by Metzger, Markus T

Subject: [patch 4/21] mm: refund memory for a locked buffer

Add a function to refund the memory of a locked buffer.

The function will be used by a worker thread to free a buffer
allocated by a different task and to refund the memory correctly.


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

Index: git-tip/include/linux/mm.h
===================================================================
--- git-tip.orig/include/linux/mm.h 2009-03-28 13:04:30.000000000 +0100
+++ git-tip/include/linux/mm.h 2009-03-28 13:07:53.000000000 +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 +1319,6 @@

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 refund_locked_buffer_memory(struct mm_struct *mm, size_t size);
#endif /* __KERNEL__ */
#endif /* _LINUX_MM_H */
Index: git-tip/mm/mlock.c
===================================================================
--- git-tip.orig/mm/mlock.c 2009-03-28 13:04:30.000000000 +0100
+++ git-tip/mm/mlock.c 2009-03-28 13:08:53.000000000 +0100
@@ -660,21 +660,20 @@
return buffer;
}

-void release_locked_buffer(void *buffer, size_t size)
+void refund_locked_buffer_memory(struct mm_struct *mm, 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)
{
- release_locked_buffer(buffer, size);
-
+ refund_locked_buffer_memory(current->mm, size);
kfree(buffer);
}
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2009-04-01 00:27:28

by Oleg Nesterov

Subject: Re: [patch 4/21] mm: refund memory for a locked buffer

On 03/31, Markus Metzger wrote:
>
> -void release_locked_buffer(void *buffer, size_t size)
> +void refund_locked_buffer_memory(struct mm_struct *mm, size_t size)

Hmm. Again, this is not bisect friendly, afaoics the kernel can't be
compiled with this patch. Irenames release_locked_buffer(), but we still
have callers (fixed by the next patches).

> void free_locked_buffer(void *buffer, size_t size)
> {
> - release_locked_buffer(buffer, size);
> -
> + refund_locked_buffer_memory(current->mm, size);
> kfree(buffer);
> }

And this one has no callers after the next patches?

Oleg.