On Wed, 7 Mar 2012, Andrea Arcangeli wrote: > On Tue, Mar 06, 2012 at 03:28:43PM -0800, Hugh Dickins wrote: > > On Thu, 1 Mar 2012, Bob Liu wrote: > > > > > Signed-off-by: Bob Liu <lliubbo@xxxxxxxxx> > > > > I agree it looks very much nicer: a patch on these lines would be good. > > > > But you've lost the comment about a return of 1 meaning "Retry later if > > split_huge_page run from under us", which I think was a helpful comment. > > > > And you've not commented on the functional change which you made: > > if page_trans_compound_anon() returns NULL, then _split() now returns > > 1 where before it returned 0. I suspect that's a reasonable change > > in a rare case, and better left simple as you have it, than slavishly > > reproduce the earlier behaviour; but I'd like to have an Ack from the > > author before we commit your modification. > > Yes, it's not a "noop", I just read the patch through the -mm flow a > few sec after reading the above. > > > But you didn't Cc Andrea whose code this is, and who understands THP > > and its races better than anybody: now Cc'ed. > > Thanks for CCing me. Returning 1 when page_trans_compound_anon returns > NULL, should still be safe, because 1 triggers the bail out path, so > it won't harm. It should be fully equivalent too because it would bail > out later in the PageAnon check if page_trans_compound_anon returned 0 > (the function was invoked only on compound pages in the first place). > > So it looks fine. Thanks, Andrea, that's good. So Bob, please resubmit with comment on return value 1 reinstated, and in the commit description explain how the slight change in operation is benign. Thanks, Hugh -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>