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_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED 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 3F272C2BA19 for ; Mon, 6 Apr 2020 13:31:30 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id CDFAE23134 for ; Mon, 6 Apr 2020 13:31:29 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="oJVNrdWd" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org CDFAE23134 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=gmail.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 2F51E8E0029; Mon, 6 Apr 2020 09:31:25 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 2A5848E000D; Mon, 6 Apr 2020 09:31:25 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 1BBC38E0029; Mon, 6 Apr 2020 09:31:25 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0008.hostedemail.com [216.40.44.8]) by kanga.kvack.org (Postfix) with ESMTP id 025258E000D for ; Mon, 6 Apr 2020 09:31:24 -0400 (EDT) Received: from smtpin11.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id AFE6B181AEF3E for ; Mon, 6 Apr 2020 13:31:24 +0000 (UTC) X-FDA: 76677516888.11.crush39_80b21144d2b23 X-HE-Tag: crush39_80b21144d2b23 X-Filterd-Recvd-Size: 3852 Received: from mail-io1-f65.google.com (mail-io1-f65.google.com [209.85.166.65]) by imf21.hostedemail.com (Postfix) with ESMTP for ; Mon, 6 Apr 2020 13:31:24 +0000 (UTC) Received: by mail-io1-f65.google.com with SMTP id o127so15754101iof.0 for ; Mon, 06 Apr 2020 06:31:24 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=1nTO/ppTreCZQCNoghFNWwHYr3bBcvv/27V77wzxMzU=; b=oJVNrdWdvjEE34EURelVe4bkx7KHKN+297iCWVtyOAC51LlFWvpaU2Gj0/sJuRnl1o RQxE8ITP0qlzu9mni0hZKY+Sm121KVwJUJZeiCHW2aDTcvfv2qpBQc8Pasdx7j9gWkKM w+/sl0vWjbCXZmXpZudglQDmXNJx53/3BNPQkA3VQKQIcCyM9UKnfI+i3LzJjF6ZCBDQ SPxLUMYR32fKG3ho5ljnZ/4W/nwrXIrbMzZwMSGZTI/7nLApBAlva5SG6etkm44u2hDU 5mSpC1asBlr0l2FZugupRqc/pUD4WBE0Alr8Y4WSPzJnPK5qDV/4cmD2F5JOhOgJNQQ+ k69g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=1nTO/ppTreCZQCNoghFNWwHYr3bBcvv/27V77wzxMzU=; b=R647qW39PtQ1pKqKZA4qgWUVWHPh5PvQiVhWMqFBNdxFwgMwdVCdZpKVTNxOYUpr16 LmXvknhTk2mMOqnQw/3cpQ648UJjfqm07gUuQhlxyRgqsF4l/MFqStFFfZoWu5oAKny4 ajmGTt3pjNEXUxUT5wH8S5l3Au5zcIuoB1BLQsNMqGyYZya8MsqzjXIatlJIW+5kDI2j kHhqj4SZQn9VG/bwPw/PKdxmiKxvcGzG7xlpXCuFtETaZjV18eJNTPfLcd1T6bujOOF4 KUA3nm1bWHH174XPD9QozCwQ2deOpkbNyKLYGppRw6/lLPT6ecMYhU8Yd3/gCCDDtL6E ia1w== X-Gm-Message-State: AGi0PuZXWO33MsRaJX1CDQvoELJBxIjotR9hzD2Z3Vv5JIPcadwUSoRm +uRvVhsVT8e/hoPb25xKPLVdgMG0fwVUobziqXU= X-Google-Smtp-Source: APiQypJHSolU3p4Xx+12hSLlIc0dvlAeBsjIsixlfGt12d4SpujalG0u9iW3vUWCgCZi17OMa7Y8UT0hXV24C3QSttY= X-Received: by 2002:a6b:c045:: with SMTP id q66mr19900037iof.10.1586179883679; Mon, 06 Apr 2020 06:31:23 -0700 (PDT) MIME-Version: 1.0 References: <1586177647-11889-1-git-send-email-laoar.shao@gmail.com> <20200406130533.GZ21484@bombadil.infradead.org> In-Reply-To: <20200406130533.GZ21484@bombadil.infradead.org> From: Yafang Shao Date: Mon, 6 Apr 2020 21:30:47 +0800 Message-ID: Subject: Re: [PATCH] mm, memcg: fix error return value of mem_cgroup_alloc() To: Matthew Wilcox Cc: Johannes Weiner , Michal Hocko , Vladimir Davydov , Andrew Morton , Linux MM 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: On Mon, Apr 6, 2020 at 9:05 PM Matthew Wilcox wrote: > > 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". > Agree with you that EBUSY is better. I will correct it. > > -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. > Thanks for your advise. I will take a look at it. Thanks Yafang