Re: [PATCH]

[Linus Torvalds <torvalds@transmeta.com>]

On Wed, 15 Aug 2001, Ben LaHaise wrote:
>
> The patch below enables vma merging for a couple of additional cases with
> anon mmaps as glibc has a habit of passing in differing flags for some
> cases (ie memory remapping, extending specific malloc blocks, etc).  This
> is to help Mozilla which ends up with thousands of vma's that are
> sequential and anonymous, but unmerged.  There may still be issues with
> mremap, but I think this is a step in the right direction.

Good catch.

However, I really think we should just mask those bits out in general:
we've already used them up by this time, and they make no sense at all to
maintain in the VMA either, so it looks like it would be a cleaner (and
shorter) patch to just do

	/* get rid of mmap-time-only flags */
	vm_flags &= ~(MAP_NORESERVE | MAP_FIXED);

just after we've checked the MAP_NORESERVE bit, and just before we check
whether we can expand an old mapping. That way the (now meaningless) bits
don't end up as noise in the vma->vm_flags, AND we guarantee that merging
doesn't merge two fields that have different "noise" in their vm_flags.

Agreed?

		Linus

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