[PATCH] unpaged: get_user_pages VM_RESERVED
Hugh Dickins [Tue, 22 Nov 2005 05:32:11 +0000 (21:32 -0800)]
The PageReserved removal in 2.6.15-rc1 prohibited get_user_pages on the areas
flagged VM_RESERVED in place of PageReserved.  That is correct in theory - we
ought not to interfere with struct pages in such a reserved area; but in
practice it broke BTTV for one.

So revert to prohibiting only on VM_IO: if someone gets into trouble with
get_user_pages on VM_RESERVED, it'll just be a "don't do that".

You can argue that videobuf_mmap_mapper shouldn't set VM_RESERVED in the first
place, but now's not the time for breaking drivers without notice.

Signed-off-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

mm/memory.c

index 2998cfc..cfce5f1 100644 (file)
@@ -968,7 +968,7 @@ int get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
                        continue;
                }
 
-               if (!vma || (vma->vm_flags & (VM_IO | VM_RESERVED))
+               if (!vma || (vma->vm_flags & VM_IO)
                                || !(vm_flags & vma->vm_flags))
                        return i ? : -EFAULT;