From c9d0bf241451a3ab7d02e1652c22b80cd7d93e8f Mon Sep 17 00:00:00 2001 From: Magnus Damm Date: Mon, 14 Dec 2009 17:59:49 -0800 Subject: [PATCH] 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 Cc: Nick Piggin Cc: Hugh Dickins Cc: Paul Mundt Cc: Jaya Kumar Cc: Arnd Bergmann Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/mmap.c | 14 +++++++++++++- 1 file changed, 13 insertions(+), 1 deletion(-) diff --git a/mm/mmap.c b/mm/mmap.c index 02c09f33df8..d9c77b2dbe9 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -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;