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=-0.6 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no 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 E846FC2BA19 for ; Mon, 6 Apr 2020 13:05:41 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id AD2A32228A for ; Mon, 6 Apr 2020 13:05:41 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="kPmtVonb" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org AD2A32228A Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 5052F8E0015; Mon, 6 Apr 2020 09:05:41 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 4B4B18E000D; Mon, 6 Apr 2020 09:05:41 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 3F26A8E0015; Mon, 6 Apr 2020 09:05:41 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0178.hostedemail.com [216.40.44.178]) by kanga.kvack.org (Postfix) with ESMTP id 283ED8E000D for ; Mon, 6 Apr 2020 09:05:41 -0400 (EDT) Received: from smtpin16.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id C94D4801B87A for ; Mon, 6 Apr 2020 13:05:40 +0000 (UTC) X-FDA: 76677452040.16.smash50_318a1f9520751 X-HE-Tag: smash50_318a1f9520751 X-Filterd-Recvd-Size: 2492 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) by imf17.hostedemail.com (Postfix) with ESMTP for ; Mon, 6 Apr 2020 13:05:40 +0000 (UTC) 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; bh=rPftdmQ+GXIEtIzjPbT/VabkRjfLLNZ+Zsi42keeacA=; b=kPmtVonbzw1+LHBfibvHpTLla7 lQVOVj2XSdG+nfB02mc0He/8np37ltKuE2pX8YyqIfxNn04yvobR4KJYvTRDeyplvjuP9APJ/T2dF WfnaG5TIYeb22lhN5oaVdtfFzfM2xFz7omjmLib0TiNh5aemtY4TXxu9da/bmix4r3oI+ECCUMSZL ekS/dNn15tbjSiKLyb/SxW1kmWOnEbc8N7IOO1GSyuP8pfqIlSra2tGTEDkfc9NIdkCESEuVNzL4z 0+ctB0EnpAE3rA+4kkYoJIdveyU2XzZ+YRBI7Vu8hkRRjJID4yUWlf+88iaRoO8DhmG+sk+nOevzW g43YLbiQ==; Received: from willy by bombadil.infradead.org with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1jLRRW-0008Ef-1A; Mon, 06 Apr 2020 13:05:34 +0000 Date: Mon, 6 Apr 2020 06:05:33 -0700 From: Matthew Wilcox To: Yafang Shao Cc: hannes@cmpxchg.org, mhocko@kernel.org, vdavydov.dev@gmail.com, akpm@linux-foundation.org, linux-mm@kvack.org Subject: Re: [PATCH] mm, memcg: fix error return value of mem_cgroup_alloc() Message-ID: <20200406130533.GZ21484@bombadil.infradead.org> References: <1586177647-11889-1-git-send-email-laoar.shao@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1586177647-11889-1-git-send-email-laoar.shao@gmail.com> 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 Mon, Apr 06, 2020 at 08:54:07AM -0400, Yafang Shao wrote: > When I run my memcg testcase which creates lots of memcgs, I found > there're unexpected out of memory logs while there're still enough > available free memory. The error log is, > mkdir: cannot create directory 'foo.65533': Cannot allocate memory > > The reason is when we try to create more than MEM_CGROUP_ID_MAX memcgs, an > -ENOMEM errno will be set by mem_cgroup_css_alloc(), but the right errno > should be -ENOSPC, as explained above the function idr_alloc(). I think idr_alloc() is wrong. I think the right errno to return here is EBUSY "Device or resource busy". > -static struct mem_cgroup *mem_cgroup_alloc(void) > +static struct mem_cgroup *mem_cgroup_alloc(long *error) The normal way to do this is to return an ERR_PTR(). See include/linux/err.h.