On Tue, May 6, 2014 at 11:13 AM, Jerome Glisse <j.glisse@xxxxxxxxx> wrote:
>
> I could grow the radix function to return some bool to avoid looping over for
> case where there is no special entry.
.. or even just a bool (or counter) associated with the mapping to
mark whether any special entries exist at all.
Also, the code to turn special entries is duplicated over and over
again, usually together with a "FIXME - what about migration failure",
so it would make sense to do that as it's own function.
But conceptually I don't hate it. I didn't much like having random
hmm_pagecache_migrate() calls in core vm code, and code like this
+ hmm_pagecache_migrate(mapping, swap);
+ spd.pages[page_nr] = find_get_page(mapping,
index + page_nr);
looks fundamentally racy, and in other places you seemed to assume
that all exceptional entries are always about hmm, which looked
questionable. But those are details. The concept of putting a special
swap entry in the mapping radix trees I don't necessarily find
objectionable per se.
Linus
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