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[209.85.220.65]) by mx.google.com with SMTPS id d11sor15123283ioq.48.2019.04.26.17.31.57 for (Google Transport Security); Fri, 26 Apr 2019 17:31:58 -0700 (PDT) Received-SPF: pass (google.com: domain of laoar.shao@gmail.com designates 209.85.220.65 as permitted sender) client-ip=209.85.220.65; Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=GRQvaMYd; spf=pass (google.com: domain of laoar.shao@gmail.com designates 209.85.220.65 as permitted sender) smtp.mailfrom=laoar.shao@gmail.com; dmarc=pass (p=NONE sp=QUARANTINE dis=NONE) header.from=gmail.com 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=2QgVvbOTbiGvVrZQMKzKXcCYAFgho+lUOq5aSkENeLo=; b=GRQvaMYd89KGckS1pHpP6tqOAL11CzuNh3uCFo5i2WlGp0J7SuHKnNADOSm2OB4ga1 PxuWwLb1xhy9Im1iGI99EpbquIzVWmLcGNM7e3CYUH7Alf6T0ZFFIxcQudgmkhZGLKNN 2bMaFfERZx/lv/HH03TiwbuLwC7iq+y0vl56KOCQFmz1KciED9xvStf0BrZOJStCzfZG /VZmN3HIcJ1p1SOzDPzbG/PBoEA9aPpVQO9qIGOZ3qlnUzZHN/k1RTsoJNg5FYDJrk/d M7gZB46NJ7m2l/pb8WQ7kxMwSvM2gZBo+UwMaQEfa3I0bytcoZr7LSyA60XdiaM/PbLo 0MHw== X-Google-Smtp-Source: APXvYqyxEKGXgzDcIfMQFY3G/X2LzeY/zhXeNH2wVvrkadH4IJQYFv/j/2aH6a/YIqdaXLJMN756YoXQbe1Vzy7YiGI= X-Received: by 2002:a5d:9a90:: with SMTP id c16mr3477445iom.295.1556325117664; Fri, 26 Apr 2019 17:31:57 -0700 (PDT) MIME-Version: 1.0 References: <1556274402-19018-1-git-send-email-laoar.shao@gmail.com> <20190426112542.bf1cd9fe8e9ed7a659642643@linux-foundation.org> In-Reply-To: <20190426112542.bf1cd9fe8e9ed7a659642643@linux-foundation.org> From: Yafang Shao Date: Sat, 27 Apr 2019 08:31:42 +0800 Message-ID: Subject: Re: [PATCH] mm/page-writeback: introduce tracepoint for wait_on_page_writeback To: Andrew Morton Cc: Jan Kara , Michal Hocko , Linux MM , shaoyafang@didiglobal.com 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 Sat, Apr 27, 2019 at 2:25 AM Andrew Morton wrote: > > On Fri, 26 Apr 2019 18:26:42 +0800 Yafang Shao wrote: > > > Recently there're some hungtasks on our server due to > > wait_on_page_writeback, and we want to know the details of this > > PG_writeback, i.e. this page is writing back to which device. > > But it is not so convenient to get the details. > > > > I think it would be better to introduce a tracepoint for diagnosing > > the writeback details. > > Fair enough, I guess. > > > --- a/include/linux/pagemap.h > > +++ b/include/linux/pagemap.h > > @@ -537,15 +537,7 @@ static inline int wait_on_page_locked_killable(struct page *page) > > > > extern void put_and_wait_on_page_locked(struct page *page); > > > > -/* > > - * Wait for a page to complete writeback > > - */ > > -static inline void wait_on_page_writeback(struct page *page) > > -{ > > - if (PageWriteback(page)) > > - wait_on_page_bit(page, PG_writeback); > > -} > > - > > +void wait_on_page_writeback(struct page *page); > > extern void end_page_writeback(struct page *page); > > void wait_for_stable_page(struct page *page); > > > > ... > > > > +/* > > + * Wait for a page to complete writeback > > + */ > > +void wait_on_page_writeback(struct page *page) > > +{ > > + if (PageWriteback(page)) { > > + trace_wait_on_page_writeback(page, page_mapping(page)); > > + wait_on_page_bit(page, PG_writeback); > > + } > > +} > > +EXPORT_SYMBOL_GPL(wait_on_page_writeback); > > But this is a stealth change to the wait_on_page_writeback() licensing. > I will get sad emails from developers of accidentally-broken > out-of-tree filesystems. > > We can discuss changing the licensing, but this isn't the way to do it! > Got it. Thanks for your explatation. Thanks Yafang