Commit b1d0e4f5 authored by Nick Piggin's avatar Nick Piggin Committed by Linus Torvalds

mm: special mapping nopage

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: default avatarNick Piggin <npiggin@suse.de>
Cc: linux-mm@kvack.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 6a306e8b
...@@ -2165,24 +2165,31 @@ int may_expand_vm(struct mm_struct *mm, unsigned long npages) ...@@ -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, static int special_mapping_fault(struct vm_area_struct *vma,
unsigned long address, int *type) struct vm_fault *vmf)
{ {
pgoff_t pgoff;
struct page **pages; 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; pgoff && *pages; ++pages)
for (pages = vma->vm_private_data; address > 0 && *pages; ++pages) pgoff--;
address -= PAGE_SIZE;
if (*pages) { if (*pages) {
struct page *page = *pages; struct page *page = *pages;
get_page(page); 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) ...@@ -2194,7 +2201,7 @@ static void special_mapping_close(struct vm_area_struct *vma)
static struct vm_operations_struct special_mapping_vmops = { static struct vm_operations_struct special_mapping_vmops = {
.close = special_mapping_close, .close = special_mapping_close,
.nopage = special_mapping_nopage, .fault = special_mapping_fault,
}; };
/* /*
......
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