Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

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

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

mm/mmap.c

+16 −9
Original line number Diff line number Diff line
@@ -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,

};



/*