Commit c9d0bf24 authored Dec 14, 2009 by Magnus Damm Committed by Linus Torvalds Dec 15, 2009

mm: uncached vma support with writenotify



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 <damm@opensource.se>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Hugh Dickins <hugh.dickins@tiscali.co.uk>
Cc: Paul Mundt <lethal@linux-sh.org>
Cc: Jaya Kumar <jayakumar.lkml@gmail.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 62c0c2f1

mm/mmap.c

+13 −1

Original line number	Diff line number	Diff line
		@@ -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;

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