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

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

[Markus Metzger]

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 <markus.t.metzger@intel.com>
---

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

[Oleg Nesterov]

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.