From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from lamorak.hansenpartnership.com (lamorak.hansenpartnership.com [198.37.111.173]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id DE2B486250; Fri, 21 Mar 2025 12:34:03 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.37.111.173 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1742560445; cv=none; b=CNEiG/vPP55b5q9gBLGbPpiOKavS+DZz06IpepnBsPvoqjHY00H9ipVtHy6LXiFuV4KnZR1he4UOZkGqzrXIo+MZxr5qGjs5mynnAYyBkYjOhD714Dd1jR6HxL7PM+q+5N3boKeYgHXvcjTdX4Zh1jKsWub0iK2cxemvIFf2H2A= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1742560445; c=relaxed/simple; bh=GFNU56b7WdHpKXPmdWPdZ2I/P7yGjJPYxXE7+9dTP5M=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=Ftv2mWlVutgjmzeCEmVe+MnMMSo4G2yMDS26uXonmCLKzIAHMgrQRdX/R7gGcMxW52XG/iA8SoQ/2mu3SqGNG/1vB+K4sBtQZ0/9ERknosNqiJ8l0ASapUwoZTVIhewWxb9/uzquoRhpLLm6b6vSH93Sf1VQRg3zVMwWOZXgfC8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=HansenPartnership.com; spf=pass smtp.mailfrom=HansenPartnership.com; dkim=pass (1024-bit key) header.d=hansenpartnership.com header.i=@hansenpartnership.com header.b=ddIDAwJi; arc=none smtp.client-ip=198.37.111.173 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=HansenPartnership.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=HansenPartnership.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=hansenpartnership.com header.i=@hansenpartnership.com header.b="ddIDAwJi" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=hansenpartnership.com; s=20151216; t=1742560442; bh=GFNU56b7WdHpKXPmdWPdZ2I/P7yGjJPYxXE7+9dTP5M=; h=Message-ID:Subject:From:To:Date:In-Reply-To:References:From; b=ddIDAwJieaefjo7z1ZfVPnDYd3rhPM/S0IgEBhmLVTn/KcXhs3IBP0cBzVrXN2mH6 M7l9aCr4mQa4GockzM9BNKINOBwxqaEJvOB3+U5zAyK6Bbp2gNK1Xp+yFXdvmx/8Lz thTbTQ5TWOWOePOehemP29IXWvAoM/D2Aj7Kwts4= Received: from lingrow.int.hansenpartnership.com (unknown [IPv6:2601:5c4:4302:c21::a774]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange x25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by lamorak.hansenpartnership.com (Postfix) with ESMTPSA id 62E191C0396; Fri, 21 Mar 2025 08:34:02 -0400 (EDT) Message-ID: <576418420308d2511a4c155cc57cf0b1420c273b.camel@HansenPartnership.com> Subject: Re: [LSF/MM/BPF TOPIC] Filesystem Suspend Resume From: James Bottomley To: Christoph Hellwig Cc: linux-fsdevel@vger.kernel.org, lsf-pc@lists.linux-foundation.org, "Rafael J. Wysocki" , Pavel Machek , Len Brown , linux-pm@vger.kernel.org Date: Fri, 21 Mar 2025 08:34:01 -0400 In-Reply-To: References: <0a76e074ef262ca857c61175dd3d0dc06b67ec42.camel@HansenPartnership.com> Autocrypt: addr=James.Bottomley@HansenPartnership.com; prefer-encrypt=mutual; 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 8mT2Eh9SkH+YVOmaKsajgZgrBxA7fWmGoxXswEVxJIFj3vW7yNc0C5HaUdYa5iGOMs4kg2ht4s7yy7NRQuh7BifWjo6BQ6k4S1H+6axZucxhSV1L6zN9d+lr3Xo/vy1unzA== Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.50.3 Precedence: bulk X-Mailing-List: linux-pm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Thu, 2025-03-20 at 22:23 -0700, Christoph Hellwig wrote: > On Thu, Mar 20, 2025 at 02:15:15PM -0400, James Bottomley wrote: > > On Thu, 2025-03-20 at 09:48 -0700, Christoph Hellwig wrote: > > [...] > > > We finally got hibernate to freeze file system on suspend, > >=20 > > I was looking for this to see if I could possibly plug something in > > for pseudo filesystems that don't have backing devices.=C2=A0 However, = I > > can't find the path where suspend causes freeze (at least the bdev > > doesn't seem to register any power notifier like the scsi block > > device does), where is the code? >=20 > Looking again I can't find it either.=C2=A0 On the internet I find a patc= h > adding it from 2006: > =20 > https://groups.google.com/g/fa.linux.kernel/c/dtxsNJ7ks58/m/mqU8SIAbvLgJ Wow google has a terrible interface. This is the lore link: https://lore.kernel.org/all/200611011200.18438.rjw@sisk.pl/ So the patch indicates where to put direct hooks in the power management but it operates via bdev_freeze/thaw() which wouldn't work for pseudo filesystems, but could be replaced by a direct hook into the vfs that would iterate over superblocks calling freeze_super/thaw_super(). > But I couldn't see if it got applied or disappaeared again somehow. > Adding the relevant maintainers. It looks like it got reposted about 5 years later as well (in the middle of a thread about xfs hibernate lockups): https://lore.kernel.org/all/201108032315.06012.rjw__14254.1066081778$131240= 6161$gmane$org@sisk.pl/ Then again 6 months later: https://lore.kernel.org/all/201201281445.49377.rjw@sisk.pl/ everything kept foundering on deadlock problems between filesystems needing threads to shrink and complete writeout and the freezing of those threads. Let me digest all that and see if we have more hope this time around. Regards, James