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[209.85.167.51]) by smtp.gmail.com with ESMTPSA id d24-v6sm1126543ljg.2.2019.01.16.09.48.51 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 16 Jan 2019 09:48:52 -0800 (PST) Received: by mail-lf1-f51.google.com with SMTP id n18so5590665lfh.6 for ; Wed, 16 Jan 2019 09:48:51 -0800 (PST) X-Received: by 2002:a19:6e0b:: with SMTP id j11mr8122372lfc.124.1547660931486; Wed, 16 Jan 2019 09:48:51 -0800 (PST) MIME-Version: 1.0 References: <20190110004424.GH27534@dastard> <20190110070355.GJ27534@dastard> <20190110122442.GA21216@nautica> <5c3e7de6.1c69fb81.4aebb.3fec@mx.google.com> <9E337EA6-7CDA-457B-96C6-E91F83742587@amacapital.net> <20190116054613.GA11670@nautica> In-Reply-To: From: Linus Torvalds Date: Thu, 17 Jan 2019 05:48:33 +1200 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH] mm/mincore: allow for making sys_mincore() privileged To: Jiri Kosina Cc: Dominique Martinet , Andy Lutomirski , Josh Snyder , Dave Chinner , Matthew Wilcox , Jann Horn , Andrew Morton , Greg KH , Peter Zijlstra , Michal Hocko , Linux-MM , kernel list , Linux API Content-Type: text/plain; charset="UTF-8" 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: Message-ID: <20190116174833.80MR4H8lotwQUg-rzlRRArluOD3tNZ5qZH5xgZRSi3E@z> On Thu, Jan 17, 2019 at 4:12 AM Jiri Kosina wrote: > > So that seems to deal with mincore() in a reasonable way indeed. > > It doesn't unfortunately really solve the preadv2(RWF_NOWAIT), nor does it > provide any good answer what to do about it, does it? As I suggested earlier in the thread, the fix for RWF_NOWAIT might be to just move the test down to after readahead. We could/should be smarter than this,but it *might* be as simple as just diff --git a/mm/filemap.c b/mm/filemap.c index 9f5e323e883e..7bcdd36e629d 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -2075,8 +2075,6 @@ static ssize_t generic_file_buffered_read( page = find_get_page(mapping, index); if (!page) { - if (iocb->ki_flags & IOCB_NOWAIT) - goto would_block; page_cache_sync_readahead(mapping, ra, filp, index, last_index - index); which starts readahead even if IOCB_NOWAIT is set and will then test IOCB_NOWAIT _later_ and not actually wait for it. Linus