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[2607:7c80:54:e::133]) by mx.google.com with ESMTPS id s23si11302160plq.81.2019.07.23.10.55.44 for (version=TLS1_3 cipher=AEAD-AES256-GCM-SHA384 bits=256/256); Tue, 23 Jul 2019 10:55:44 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of willy@infradead.org designates 2607:7c80:54:e::133 as permitted sender) client-ip=2607:7c80:54:e::133; Authentication-Results: mx.google.com; dkim=pass header.i=@infradead.org header.s=bombadil.20170209 header.b=Pjwch1Qk; spf=pass (google.com: best guess record for domain of willy@infradead.org designates 2607:7c80:54:e::133 as permitted sender) smtp.mailfrom=willy@infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=bl0M5NSk0nmCZFb/3HXW8+xYe1ZmbQXUvDwYm6YUgfk=; b=Pjwch1QkqUDzGn63jiv3m7mO8 eZhAGD1vxQSBR0t+nWjWFBkokMonpycyRfXPkWsfe4FEf9lJAWvfoGb/0yPbVYiH9z3Hhh6xXEDg5 zr4VUm0R/xlzryCVOr6PmUmENT6zpTuuKdMQwg5/UK7F1kaOI3VpvG89/rWSIF6RwvvpvQ3MpXHWN yQ8muS9Odn+YEFoGSCibtUSbyROrieftl5Bnz5BTaI8Trw3xuvq+Cft1SdWFJ7V6Gtt+aMU6hGGal 5DaKTYERMJC5hF8XIY0NnhcBt26AgMGDV9jAY6zOWTBbVmIBad4tH4OAALgaUWdrWmFpnTCeI5V+N 5tdpZCS5A==; Received: from willy by bombadil.infradead.org with local (Exim 4.92 #3 (Red Hat Linux)) id 1hpz0p-0004AD-Lp; Tue, 23 Jul 2019 17:55:43 +0000 Date: Tue, 23 Jul 2019 10:55:43 -0700 From: Matthew Wilcox To: Jeff Layton Cc: akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, viro@zeniv.linux.org.uk, lhenriques@suse.com, cmaiolino@redhat.com, Christoph Hellwig Subject: Re: [PATCH] mm: check for sleepable context in kvfree Message-ID: <20190723175543.GL363@bombadil.infradead.org> References: <20190723131212.445-1-jlayton@kernel.org> <3622a5fe9f13ddfd15b262dbeda700a26c395c2a.camel@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <3622a5fe9f13ddfd15b262dbeda700a26c395c2a.camel@kernel.org> User-Agent: Mutt/1.11.4 (2019-03-13) 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 Tue, Jul 23, 2019 at 01:52:36PM -0400, Jeff Layton wrote: > On Tue, 2019-07-23 at 09:12 -0400, Jeff Layton wrote: > > A lot of callers of kvfree only go down the vfree path under very rare > > circumstances, and so may never end up hitting the might_sleep_if in it. > > Ensure that when kvfree is called, that it is operating in a context > > where it is allowed to sleep. > > > > Cc: Alexander Viro > > Cc: Luis Henriques > > Signed-off-by: Jeff Layton > > --- > > mm/util.c | 2 ++ > > 1 file changed, 2 insertions(+) > > > > FWIW, I started looking at this after Luis sent me some ceph patches > that fixed a few of these problems. I have not done extensive testing > with this patch, so maybe consider this an RFC for now. > > HCH points out that xfs uses kvfree as a generic "free this no matter > what it is" sort of wrapper and expects the callers to work out whether > they might be freeing a vmalloc'ed address. If that sort of usage turns > out to be prevalent, then we may need another approach to clean this up. I think it's a bit of a landmine, to be honest. How about we have kvfree() call vfree_atomic() instead?