linux-kernel - Re: [patch 12/13] GRU Driver V3 - export is_uv_system(), zap_page_range() & follow

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Date:	Mon, 7 Jul 2008 12:58:58 -0500
From:	Jack Steiner <steiner@....com>
To:	Christoph Hellwig <hch@...radead.org>, cl@...ux-foundation.org,
	hugh@...itas.com
Cc:	akpm@...l.org, linux-kernel@...r.kernel.org, mingo@...e.hu,
	tglx@...utronix.de, holt@....com, andrea@...ranet.com,
	linux-mm@...ck.org
Subject: Re: [patch 12/13] GRU Driver V3 -  export is_uv_system(), zap_page_range() & follow_page()

On Fri, Jul 04, 2008 at 03:39:26AM -0400, Christoph Hellwig wrote:
> On Thu, Jul 03, 2008 at 04:34:00PM -0500, steiner@....com wrote:
> > +EXPORT_SYMBOL_GPL(zap_page_range);
> >  
> 
> NACK.
> 

I agree that zap_pages_range() is more general than what is needed.

How about the following. This should prevent abuse of the API &
provide what (I think) drivers need.

Verified with GRU & XPMEM.


--- jack

--------------------------------------------------------------------------------------------
Add function to unmap driver ptes.

zap_vma_ptes() is intended to be used by drivers to unmap
ptes assigned to the driver private vmas. This interface is
similar to zap_page_range() but is less general & less likely to
be abused.


Signed-off-by: Jack Steiner <steiner@....com>

---
 include/linux/mm.h |    2 ++
 mm/memory.c        |   23 +++++++++++++++++++++++
 2 files changed, 25 insertions(+)

Index: linux/include/linux/mm.h
===================================================================
--- linux.orig/include/linux/mm.h	2008-07-07 12:22:17.809892803 -0500
+++ linux/include/linux/mm.h	2008-07-07 12:22:56.126695482 -0500
@@ -742,6 +742,8 @@ struct zap_details {
 struct page *vm_normal_page(struct vm_area_struct *vma, unsigned long addr,
 		pte_t pte);
 
+int zap_vma_ptes(struct vm_area_struct *vma, unsigned long address,
+		unsigned long size);
 unsigned long zap_page_range(struct vm_area_struct *vma, unsigned long address,
 		unsigned long size, struct zap_details *);
 unsigned long unmap_vmas(struct mmu_gather **tlb,
Index: linux/mm/memory.c
===================================================================
--- linux.orig/mm/memory.c	2008-07-07 12:22:18.357961503 -0500
+++ linux/mm/memory.c	2008-07-07 12:31:51.097688882 -0500
@@ -978,6 +978,29 @@ unsigned long zap_page_range(struct vm_a
 }
 EXPORT_SYMBOL_GPL(zap_page_range);
 
+/**
+ * zap_vma_ptes - remove ptes mapping the vma
+ * @vma: vm_area_struct holding ptes to be zapped
+ * @address: starting address of pages to zap
+ * @size: number of bytes to zap
+ *
+ * This function only unmaps ptes assigned to VM_PFNMAP vmas.
+ *
+ * The entire address range must be fully contained within the vma.
+ *
+ * Returns 0 if successful.
+ */
+int zap_vma_ptes(struct vm_area_struct *vma, unsigned long address,
+		unsigned long size)
+{
+	if (address < vma->vm_start || address + size > vma->vm_end ||
+	    		!(vma->vm_flags & VM_PFNMAP))
+		return -1;
+	zap_page_range(vma, address, size, NULL);
+	return 0;
+}
+EXPORT_SYMBOL_GPL(zap_vma_ptes);
+
 /*
  * Do a quick page-table lookup for a single page.
  */
--
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