Re: [PATCH 02/11] unpaged: private write VM_RESERVED

Dave Jones
2005-11-17T19:41:21Z

On Thu, Nov 17, 2005 at 07:30:04PM +0000, Hugh Dickins wrote:
> The PageReserved removal in 2.6.15-rc1 issued a "deprecated" message
> when you tried to mmap or mprotect MAP_PRIVATE PROT_WRITE a VM_RESERVED,
> and failed with -EACCES: because do_wp_page lacks the refinement to COW
> pages in those areas, nor do we expect to find anonymous pages in them;
> and it seemed just bloat to add code for handling such a peculiar case.
> But immediately it caused vbetool and ddcprobe (using lrmi) to fail.
>
> So revert the "deprecated" messages, letting mmap and mprotect succeed.
> But leave do_wp_page's BUG_ON(vma->vm_flags & VM_RESERVED) in place
> until we've added the code to do it right: so this particular patch is
> only good if the app doesn't really need to write to that private area.
>
> Dave Jones has changed vbetool & ddcprobe to use MAP_SHARED or PROT_READ
> just as well, but we don't want to force people to update their tools.

Actually Dave Miller did the detective work on that one, I just
rebuilt some packages, and spread the good word :)

Dave