Re: [PATCH 02/30] mm: gfp_to_alloc_flags()
From: Neil Brown <hidden>
Date: 2008-08-12 05:02:10
Also in:
linux-mm, lkml
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 <redacted> --- 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:
quoted hunk
@@ -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