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nommu: Correct kobjsize() page validity checks. 

This implements a few changes on top of the recent kobjsize() refactoring
introduced by commit 6cfd53fc03.

As Christoph points out:

	virt_to_head_page cannot return NULL. virt_to_page also
	does not return NULL. pfn_valid() needs to be used to
	figure out if a page is valid.  Otherwise the page struct
	reference that was returned may have PageReserved() set
	to indicate that it is not a valid page.

As discussed further in the thread, virt_addr_valid() is the preferable
way to validate the object pointer in this case. In addition to fixing
up the reserved page case, it also has the benefit of encapsulating the
hack introduced by commit 4016a1390d on
the impacted platforms, allowing us to get rid of the extra checking in
kobjsize() for the platforms that don't perform this type of bizarre
memory_end abuse (every nommu platform that isn't blackfin). If blackfin
decides to get in line with every other platform and use PageReserved
for the DMA pages in question, kobjsize() will also continue to work
fine.

It also turns out that compound_order() will give us back 0-order for
non-head pages, so we can get rid of the PageCompound check and just
use compound_order() directly. Clean that up while we're at it.

Signed-off-by: Paul Mundt <lethal@linux-sh.org>
Reviewed-by: Christoph Lameter <clameter@sgi.com>
Acked-by: David Howells <dhowells@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Paul Mundt 2008-06-12 16:29:55 +09:00 committed by Linus Torvalds
parent f969c5672b
commit 5a1603be58
1 changed files with 3 additions and 18 deletions
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21
mm/nommu.c
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@ -104,21 +104,15 @@ EXPORT_SYMBOL(vmtruncate);
unsigned int kobjsize(const void *objp)
{
struct page *page;
int order = 0;
/*
* If the object we have should not have ksize performed on it,
* return size of 0
*/
if (!objp)
return 0;
if ((unsigned long)objp >= memory_end)
if (!objp || !virt_addr_valid(objp))
return 0;
page = virt_to_head_page(objp);
if (!page)
return 0;
/*
* If the allocator sets PageSlab, we know the pointer came from
@ -129,18 +123,9 @@ unsigned int kobjsize(const void *objp)
/*
* The ksize() function is only guaranteed to work for pointers
* returned by kmalloc(). So handle arbitrary pointers, that we expect
* always to be compound pages, here.
* returned by kmalloc(). So handle arbitrary pointers here.
*/
if (PageCompound(page))
order = compound_order(page);
/*
* Finally, handle arbitrary pointers that don't set PageSlab.
* Default to 0-order in the case when we're unable to ksize()
* the object.
*/
return PAGE_SIZE << order;
return PAGE_SIZE << compound_order(page);
}
/*