From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-9.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4FD3AC2BA83 for ; Wed, 12 Feb 2020 10:14:03 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 272CC2082F for ; Wed, 12 Feb 2020 10:14:03 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 272CC2082F Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.cz Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id B2BAF6B0419; Wed, 12 Feb 2020 05:14:02 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id ADC7C6B041B; Wed, 12 Feb 2020 05:14:02 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 9F2066B041C; Wed, 12 Feb 2020 05:14:02 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id 8676D6B0419 for ; Wed, 12 Feb 2020 05:14:02 -0500 (EST) Received: from smtpin16.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id 51AE72DFA for ; Wed, 12 Feb 2020 10:14:02 +0000 (UTC) X-FDA: 76481064324.16.chair80_4051bfa80af13 X-HE-Tag: chair80_4051bfa80af13 X-Filterd-Recvd-Size: 2147 Received: from mx2.suse.de (mx2.suse.de [195.135.220.15]) by imf12.hostedemail.com (Postfix) with ESMTP for ; Wed, 12 Feb 2020 10:14:01 +0000 (UTC) X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id 784E2AC46; Wed, 12 Feb 2020 10:14:00 +0000 (UTC) Received: by quack2.suse.cz (Postfix, from userid 1000) id C55B51E0E01; Wed, 12 Feb 2020 11:13:59 +0100 (CET) From: Jan Kara To: Andrew Morton Cc: , Josef Bacik , Robert Stupp , Minchan Kim , Jan Kara Subject: [PATCH] mm: Don't bother dropping mmap_sem for zero size readahead Date: Wed, 12 Feb 2020 11:13:56 +0100 Message-Id: <20200212101356.30759-1-jack@suse.cz> X-Mailer: git-send-email 2.16.4 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: When handling a page fault, we drop mmap_sem to start async readahead so that we don't block on IO submission with mmap_sem held. However there's no point to drop mmap_sem in case readahead is disabled. Handle that case to avoid pointless dropping of mmap_sem and retrying the fault. This was actually reported to block mlockall(MCL_CURRENT) indefinitely. Fixes: 6b4c9f446981 ("filemap: drop the mmap_sem for all blocking operations") Reported-by: Minchan Kim Reported-by: Robert Stupp Signed-off-by: Jan Kara --- mm/filemap.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) Andrew, could you please pick up this patch? Minchan also tripped over this bug... diff --git a/mm/filemap.c b/mm/filemap.c index 1146fcfa3215..3d39c437b07e 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -2458,7 +2458,7 @@ static struct file *do_async_mmap_readahead(struct vm_fault *vmf, pgoff_t offset = vmf->pgoff; /* If we don't want any read-ahead, don't bother */ - if (vmf->vma->vm_flags & VM_RAND_READ) + if (vmf->vma->vm_flags & VM_RAND_READ || !ra->ra_pages) return fpin; if (ra->mmap_miss > 0) ra->mmap_miss--; -- 2.16.4