From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-f71.google.com (mail-wm0-f71.google.com [74.125.82.71]) by kanga.kvack.org (Postfix) with ESMTP id 03F4B6B0003 for ; Sun, 27 May 2018 08:47:34 -0400 (EDT) Received: by mail-wm0-f71.google.com with SMTP id f188-v6so6552211wme.2 for ; Sun, 27 May 2018 05:47:33 -0700 (PDT) Received: from mx0a-001b2d01.pphosted.com (mx0b-001b2d01.pphosted.com. [148.163.158.5]) by mx.google.com with ESMTPS id j9-v6si8470544wra.424.2018.05.27.05.47.31 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sun, 27 May 2018 05:47:32 -0700 (PDT) Received: from pps.filterd (m0098413.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.22/8.16.0.22) with SMTP id w4RChjQx071898 for ; Sun, 27 May 2018 08:47:31 -0400 Received: from e06smtp10.uk.ibm.com (e06smtp10.uk.ibm.com [195.75.94.106]) by mx0b-001b2d01.pphosted.com with ESMTP id 2j7mg3mpp3-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Sun, 27 May 2018 08:47:30 -0400 Received: from localhost by e06smtp10.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Sun, 27 May 2018 13:47:29 +0100 Date: Sun, 27 May 2018 15:47:22 +0300 From: Mike Rapoport Subject: Re: [PATCH] doc: document scope NOFS, NOIO APIs References: <20180424183536.GF30619@thunk.org> <20180524114341.1101-1-mhocko@kernel.org> <20180524221715.GY10363@dastard> <20180525081624.GH11881@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180525081624.GH11881@dhcp22.suse.cz> Message-Id: <20180527124721.GA4522@rapoport-lnx> Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko Cc: Dave Chinner , Jonathan Corbet , LKML , linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, "Darrick J. Wong" , David Sterba On Fri, May 25, 2018 at 10:16:24AM +0200, Michal Hocko wrote: > On Fri 25-05-18 08:17:15, Dave Chinner wrote: > > On Thu, May 24, 2018 at 01:43:41PM +0200, Michal Hocko wrote: > [...] > > > +FS/IO code then simply calls the appropriate save function right at the > > > +layer where a lock taken from the reclaim context (e.g. shrinker) and > > > +the corresponding restore function when the lock is released. All that > > > +ideally along with an explanation what is the reclaim context for easier > > > +maintenance. > > > > This paragraph doesn't make much sense to me. I think you're trying > > to say that we should call the appropriate save function "before > > locks are taken that a reclaim context (e.g a shrinker) might > > require access to." > > > > I think it's also worth making a note about recursive/nested > > save/restore stacking, because it's not clear from this description > > that this is allowed and will work as long as inner save/restore > > calls are fully nested inside outer save/restore contexts. > > Any better? > > -FS/IO code then simply calls the appropriate save function right at the > -layer where a lock taken from the reclaim context (e.g. shrinker) and > -the corresponding restore function when the lock is released. All that > -ideally along with an explanation what is the reclaim context for easier > -maintenance. > +FS/IO code then simply calls the appropriate save function before any > +lock shared with the reclaim context is taken. The corresponding > +restore function when the lock is released. All that ideally along with Maybe: "The corresponding restore function is called when the lock is released" > +an explanation what is the reclaim context for easier maintenance. > + > +Please note that the proper pairing of save/restore function allows nesting > +so memalloc_noio_save is safe to be called from an existing NOIO or NOFS scope. so it is safe to call memalloc_noio_save from an existing NOIO or NOFS scope > What about __vmalloc(GFP_NOFS) > ============================== > -- > Michal Hocko > SUSE Labs > -- Sincerely yours, Mike.