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Date: Thu, 26 Jan 2017 12:04:13 +0100 From: Daniel Borkmann <daniel@...earbox.net> To: Michal Hocko <mhocko@...nel.org> CC: Alexei Starovoitov <alexei.starovoitov@...il.com>, Andrew Morton <akpm@...ux-foundation.org>, Vlastimil Babka <vbabka@...e.cz>, Mel Gorman <mgorman@...e.de>, Johannes Weiner <hannes@...xchg.org>, linux-mm <linux-mm@...ck.org>, LKML <linux-kernel@...r.kernel.org>, "netdev@...r.kernel.org" <netdev@...r.kernel.org>, marcelo.leitner@...il.com Subject: Re: [PATCH 0/6 v3] kvmalloc On 01/26/2017 11:32 AM, Michal Hocko wrote: > On Thu 26-01-17 11:08:02, Michal Hocko wrote: >> On Thu 26-01-17 10:36:49, Daniel Borkmann wrote: >>> On 01/26/2017 08:43 AM, Michal Hocko wrote: >>>> On Wed 25-01-17 21:16:42, Daniel Borkmann wrote: >> [...] >>>>> I assume that kvzalloc() is still the same from [1], right? If so, then >>>>> it would unfortunately (partially) reintroduce the issue that was fixed. >>>>> If you look above at flags, they're also passed to __vmalloc() to not >>>>> trigger OOM in these situations I've experienced. >>>> >>>> Pushing __GFP_NORETRY to __vmalloc doesn't have the effect you might >>>> think it would. It can still trigger the OOM killer becauset the flags >>>> are no propagated all the way down to all allocations requests (e.g. >>>> page tables). This is the same reason why GFP_NOFS is not supported in >>>> vmalloc. >>> >>> Ok, good to know, is that somewhere clearly documented (like for the >>> case with kmalloc())? >> >> I am afraid that we really suck on this front. I will add something. > > So I have folded the following to the patch 1. It is in line with > kvmalloc and hopefully at least tell more than the current code. > --- > diff --git a/mm/vmalloc.c b/mm/vmalloc.c > index d89034a393f2..6c1aa2c68887 100644 > --- a/mm/vmalloc.c > +++ b/mm/vmalloc.c > @@ -1741,6 +1741,13 @@ void *__vmalloc_node_range(unsigned long size, unsigned long align, > * Allocate enough pages to cover @size from the page level > * allocator with @gfp_mask flags. Map them into contiguous > * kernel virtual space, using a pagetable protection of @prot. > + * > + * Reclaim modifiers in @gfp_mask - __GFP_NORETRY, __GFP_REPEAT > + * and __GFP_NOFAIL are not supported We could probably also mention that __GFP_ZERO in @gfp_mask is supported, though. > + * Any use of gfp flags outside of GFP_KERNEL should be consulted > + * with mm people. Just a question: should that read 'GFP_KERNEL | __GFP_HIGHMEM' as that is what vmalloc() resp. vzalloc() and others pass as flags? > + * > */ Sounds good otherwise, thanks Michal! > static void *__vmalloc_node(unsigned long size, unsigned long align, > gfp_t gfp_mask, pgprot_t prot,
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