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mm: uncached vma support with writenotify

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Modify the generic mmap() code to keep the cache attribute in
vma->vm_page_prot regardless if writenotify is enabled or not.  Without
this patch the cache configuration selected by f_op->mmap() is overwritten
if writenotify is enabled, making it impossible to keep the vma uncached.

Needed by drivers such as drivers/video/sh_mobile_lcdcfb.c which uses
deferred io together with uncached memory.

Signed-off-by: Magnus Damm <[email protected]>
Cc: Nick Piggin <[email protected]>
Cc: Hugh Dickins <[email protected]>
Cc: Paul Mundt <[email protected]>
Cc: Jaya Kumar <[email protected]>
Cc: Arnd Bergmann <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
This commit is contained in:
Magnus Damm authored and Linus Torvalds committed 2009-12-15 08:53:21 -08:00
1 parent 62c0c2f198
commit c9d0bf2414
1 file changed
+13 -1
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mm/mmap.c
+13 -1
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@@ -1198,8 +1198,20 @@ munmap_back:
goto free_vma;
}
if (vma_wants_writenotify(vma))
if (vma_wants_writenotify(vma)) {
pgprot_t pprot = vma->vm_page_prot;
/* Can vma->vm_page_prot have changed??
*
* Answer: Yes, drivers may have changed it in their
* f_op->mmap method.
*
* Ensures that vmas marked as uncached stay that way.
*/
vma->vm_page_prot = vm_get_page_prot(vm_flags & ~VM_SHARED);
if (pgprot_val(pprot) == pgprot_val(pgprot_noncached(pprot)))
vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
}
vma_link(mm, vma, prev, rb_link, rb_parent);
file = vma->vm_file;