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mm: special mapping nopage

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Convert special mapping install from nopage to fault.

Because the "vm_file" is NULL for the special mapping, the generic VM
code has messed up "vm_pgoff" thinking that it's an anonymous mapping
and the offset does't matter.  For that reason, we need to undo the
vm_pgoff offset that got added into vmf->pgoff.

[ We _really_ should clean that up - either by making this whole special
  mapping code just use a real file entry rather than that ugly array of
  "struct page" pointers, or by just making the VM code realize that
  even if vm_file is NULL it may not be a regular anonymous mmap.
							 - Linus ]

Signed-off-by: Nick Piggin <npiggin@suse.de>
Cc: linux-mm@kvack.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Nick Piggin 2008-02-09 01:15:19 +01:00 committed by Linus Torvalds
parent 6a306e8b4c
commit b1d0e4f535
1 changed files with 16 additions and 9 deletions
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25
mm/mmap.c
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@ -2165,24 +2165,31 @@ int may_expand_vm(struct mm_struct *mm, unsigned long npages)
}
static struct page *special_mapping_nopage(struct vm_area_struct *vma,
unsigned long address, int *type)
static int special_mapping_fault(struct vm_area_struct *vma,
struct vm_fault *vmf)
{
pgoff_t pgoff;
struct page **pages;
BUG_ON(address < vma->vm_start || address >= vma->vm_end);
/*
* special mappings have no vm_file, and in that case, the mm
* uses vm_pgoff internally. So we have to subtract it from here.
* We are allowed to do this because we are the mm; do not copy
* this code into drivers!
*/
pgoff = vmf->pgoff - vma->vm_pgoff;
address -= vma->vm_start;
for (pages = vma->vm_private_data; address > 0 && *pages; ++pages)
address -= PAGE_SIZE;
for (pages = vma->vm_private_data; pgoff && *pages; ++pages)
pgoff--;
if (*pages) {
struct page *page = *pages;
get_page(page);
return page;
vmf->page = page;
return 0;
}
return NOPAGE_SIGBUS;
return VM_FAULT_SIGBUS;
}
/*
@ -2194,7 +2201,7 @@ static void special_mapping_close(struct vm_area_struct *vma)
static struct vm_operations_struct special_mapping_vmops = {
.close = special_mapping_close,
.nopage = special_mapping_nopage,
.fault = special_mapping_fault,
};
/*