[patch] 2.5 vm bugfix

[patch] 2.5 vm bugfix

[Gerd Knorr]

  Hi,

2.5.x kernels don't look at the VM_DONTEXPAND flag when merging
multiple vmas into one.  Fix below.

  Gerd

--- linux-2.5.65/mm/mmap.c	2003-03-21 13:03:28.377764776 +0100
+++ linux/mm/mmap.c	2003-03-21 13:09:52.981296152 +0100
@@ -379,6 +379,8 @@
 can_vma_merge_before(struct vm_area_struct *vma, unsigned long vm_flags,
 	struct file *file, unsigned long vm_pgoff, unsigned long size)
 {
+	if ((vma->vm_flags & VM_DONTEXPAND) || (vm_flags & VM_DONTEXPAND))
+		return 0;
 	if (vma->vm_file == file && vma->vm_flags == vm_flags) {
 		if (!file)
 			return 1;	/* anon mapping */
@@ -396,6 +398,8 @@
 can_vma_merge_after(struct vm_area_struct *vma, unsigned long vm_flags,
 	struct file *file, unsigned long vm_pgoff)
 {
+	if ((vma->vm_flags & VM_DONTEXPAND) || (vm_flags & VM_DONTEXPAND))
+		return 0;
 	if (vma->vm_file == file && vma->vm_flags == vm_flags) {
 		unsigned long vma_size;
 

Re: [patch] 2.5 vm bugfix

[Andrew Morton]

Gerd Knorr <kraxel@bytesex.org> wrote:
>
>   Hi,
> 
> 2.5.x kernels don't look at the VM_DONTEXPAND flag when merging
> multiple vmas into one.  Fix below.

There is but one user of VM_DONTEXPAND in the kernel, and that is you ;)

Can you describe exactly why this driver requires DONTEXPAND?  ie: how does
the driver work, and why is it special?

If there is some alternative way of providing the same behaviour we could
remove VM_DONTEXPAND, which would be nice.

Thanks.