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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