Messages in this thread | | | From | Neil Brown <> | Date | Tue, 12 Aug 2008 15:01:36 +1000 | Subject | Re: [PATCH 02/30] mm: gfp_to_alloc_flags() |
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On Thursday July 24, a.p.zijlstra@chello.nl wrote: > Factor out the gfp to alloc_flags mapping so it can be used in other places. > > Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> > --- > mm/internal.h | 10 +++++ > mm/page_alloc.c | 95 +++++++++++++++++++++++++++++++------------------------- > 2 files changed, 64 insertions(+), 41 deletions(-)
This patch all looks "obviously correct" and a nice factorisation of code, except the last little bit:
> @@ -1618,6 +1627,10 @@ nofail_alloc: > if (!wait) > goto nopage; > > + /* Avoid recursion of direct reclaim */ > + if (p->flags & PF_MEMALLOC) > + goto nopage; > + > cond_resched(); > > /* We now go into synchronous reclaim */ > > --
I don't remember seeing it before (though my memory is imperfect) and it doesn't seem to fit with the rest of the patch (except spatially).
There is a test above for PF_MEMALLOC which will result in a "goto" somewhere else unless "in_interrupt()". There is immediately above a test for "!wait". So the only way this test can fire is when in_interrupt and wait. But if that happens, then the might_sleep_if(wait) at the top should have thrown a warning... It really shouldn't happen.
So it looks like it is useless code: there is already protection against recursion in this case.
Did I miss something? If I did, maybe more text in the changelog entry (or the comment) would help.
Thanks, NeilBrown
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