UBI fastmap used PEB search

[Brian Pomerantz]

I have been doing some profiling on why it takes UBI attach longer as UBI volumes fill up.  I found that the majority of time takes place in fastmap.c during the search of the used PEB list when matching for the volume's LEBs.  Specifically, I saw that the inner loop "list_for_each_entry(tmp_aeb, &used, u.list)" gets hit a LOT.  The time it takes to search this list can be reduced if the attached patch is used, all it does is put a break in the loop when the pnum is matched.  This seems so obvious I figure there must be a reason it isn't done this way and I'm just missing it, is the patch valid or will it cause issues?  I'm also wondering if anyone has tried building the used list as a RB tree instead to further reduce the time spent spinning through the list.


--Brian

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