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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>
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14
mm/mmap.c
14
mm/mmap.c
@ -1198,8 +1198,20 @@ munmap_back:
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goto free_vma;
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}
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if (vma_wants_writenotify(vma))
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if (vma_wants_writenotify(vma)) {
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pgprot_t pprot = vma->vm_page_prot;
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/* Can vma->vm_page_prot have changed??
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*
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* Answer: Yes, drivers may have changed it in their
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* f_op->mmap method.
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*
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* Ensures that vmas marked as uncached stay that way.
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*/
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vma->vm_page_prot = vm_get_page_prot(vm_flags & ~VM_SHARED);
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if (pgprot_val(pprot) == pgprot_val(pgprot_noncached(pprot)))
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vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
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}
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vma_link(mm, vma, prev, rb_link, rb_parent);
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file = vma->vm_file;
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