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Date: Thu, 17 Mar 2016 14:21:40 +0100 From: Roman Peniaev <r.peniaev@...il.com> To: Chris Wilson <chris@...is-wilson.co.uk>, Roman Peniaev <r.peniaev@...il.com>, intel-gfx@...ts.freedesktop.org, Andrew Morton <akpm@...ux-foundation.org>, David Rientjes <rientjes@...gle.com>, Mel Gorman <mgorman@...hsingularity.net>, linux-mm@...ck.org, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org> Subject: Re: [PATCH 1/2] mm/vmap: Add a notifier for when we run out of vmap address space On Thu, Mar 17, 2016 at 1:57 PM, Chris Wilson <chris@...is-wilson.co.uk> wrote: > On Thu, Mar 17, 2016 at 01:37:06PM +0100, Roman Peniaev wrote: >> > + freed = 0; >> > + blocking_notifier_call_chain(&vmap_notify_list, 0, &freed); >> >> It seems to me that alloc_vmap_area() was designed not to sleep, >> at least on GFP_NOWAIT path (__GFP_DIRECT_RECLAIM is not set). >> >> But blocking_notifier_call_chain() might sleep. > > Indeed, I had not anticipated anybody using GFP_ATOMIC or equivalently > restrictive gfp_t for vmap and yes there are such callers. > > Would guarding the notifier with gfp & __GFP_DIRECT_RECLAIM and > !(gfp & __GFP_NORETRY) == be sufficient? Is that enough for GFP_NOFS? I would use gfpflags_allow_blocking() for that purpose. Roman
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