Re: [PATCH 3/5] mm, page_owner: copy page owner info during migration

From: Vlastimil Babka
Date: Thu Nov 19 2015 - 11:46:20 EST

On 11/08/2015 10:29 PM, Hugh Dickins wrote:

Would it be possible to move that line into migrate_page_copy()?

I don't think it's wrong where you placed it, but that block is really
about resetting the old page ready for freeing, and I'd prefer to keep
all the transference of properties from old to new in migrate_page_copy()
if we can.

OK, makes sense, will do in v2.

But check how that behaves in the migrate_misplaced_transhuge_page()
case: I haven't studied long enough, but I think you may have been missing
to copy_page_owner in that case;

You're right, I missed that path :/

but beware of its "fail_putback", which
for some things nastily entails undoing what's already been done.

Yeah, I think I don't need to reset page owner info in the fail_putback path, for the same reason I don't reset it from the old page when migration is successful. The page is going to be freed anyway, and if it somehow hits a bug before that, we will still have something to print (after patch 5).


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