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[192.55.52.151]) by mx.google.com with ESMTPS id k10si6595312pgc.9.2019.06.20.09.10.45 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 20 Jun 2019 09:10:45 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of alexander.h.duyck@linux.intel.com designates 192.55.52.151 as permitted sender) client-ip=192.55.52.151; Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of alexander.h.duyck@linux.intel.com designates 192.55.52.151 as permitted sender) smtp.mailfrom=alexander.h.duyck@linux.intel.com; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=intel.com X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga007.jf.intel.com ([10.7.209.58]) by fmsmga107.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 20 Jun 2019 09:10:45 -0700 X-IronPort-AV: E=Sophos;i="5.63,397,1557212400"; d="scan'208";a="150979509" Received: from ahduyck-desk1.jf.intel.com ([10.7.198.76]) by orsmga007-auth.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 20 Jun 2019 09:10:44 -0700 Message-ID: <2299c1a5b8773c955e7d0c3803ad3fc6c83c127a.camel@linux.intel.com> Subject: Re: [PATCH] mm: fix regression with deferred struct page init From: Alexander Duyck To: Juergen Gross , xen-devel@lists.xenproject.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Date: Thu, 20 Jun 2019 09:10:44 -0700 In-Reply-To: <20190620160821.4210-1-jgross@suse.com> References: <20190620160821.4210-1-jgross@suse.com> Content-Type: text/plain; charset="UTF-8" User-Agent: Evolution 3.30.5 (3.30.5-1.fc29) MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Thu, 2019-06-20 at 18:08 +0200, Juergen Gross wrote: > Commit 0e56acae4b4dd4a9 ("mm: initialize MAX_ORDER_NR_PAGES at a time > instead of doing larger sections") is causing a regression on some > systems when the kernel is booted as Xen dom0. > > The system will just hang in early boot. > > Reason is an endless loop in get_page_from_freelist() in case the first > zone looked at has no free memory. deferred_grow_zone() is always > returning true due to the following code snipplet: > > /* If the zone is empty somebody else may have cleared out the zone */ > if (!deferred_init_mem_pfn_range_in_zone(&i, zone, &spfn, &epfn, > first_deferred_pfn)) { > pgdat->first_deferred_pfn = ULONG_MAX; > pgdat_resize_unlock(pgdat, &flags); > return true; > } > > This in turn results in the loop as get_page_from_freelist() is > assuming forward progress can be made by doing some more struct page > initialization. > > Cc: Alexander Duyck > Fixes: 0e56acae4b4dd4a9 ("mm: initialize MAX_ORDER_NR_PAGES at a time instead of doing larger sections") > Suggested-by: Alexander Duyck > Signed-off-by: Juergen Gross Acked-by: Alexander Duyck > --- > mm/page_alloc.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index d66bc8abe0af..8e3bc949ebcc 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -1826,7 +1826,8 @@ deferred_grow_zone(struct zone *zone, unsigned int order) > first_deferred_pfn)) { > pgdat->first_deferred_pfn = ULONG_MAX; > pgdat_resize_unlock(pgdat, &flags); > - return true; > + /* Retry only once. */ > + return first_deferred_pfn != ULONG_MAX; > } > > /*