From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 A65EB22301; Sat, 23 Nov 2024 18:47:29 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1732387649; cv=none; b=cp+0zWKpcF6ivC3YsYXHe6bNrC5MvnUPxBMZlQue5KyklohHgmFlxFrNt8JuaMtV+rI+s69BRCrA3mER1x+CD8sIT7nI8u+u82owqoWbERRKWPAlpFva6YTuPeVmrs/eJUfyI2OnduXCtvNQkH2SsveLQ+Go6H3UlN2a5a9/ySU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1732387649; c=relaxed/simple; bh=BSv4aD9d5H9bVWz+JcZvftPNCXHFcxmKlQmYiEoonkU=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=sDJ8FmSboEp3C1YNMISd1JdR5V4WSR0y5NgLPBlxTPZC8AlYQtQtdbYrgUmZUIxf+hM8nyuzzkFVQ5hx70GD7aL7WRAhK2vQ/n0lQ5lt6tMxvMs28Qm+Id7UE8rsxGBJ108Mu33rAF56R1VfDxZpy6BsI4nbwHOclZYtbjITvcY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=nrMgvjTQ; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="nrMgvjTQ" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9B6EDC4CED0; Sat, 23 Nov 2024 18:47:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1732387649; bh=BSv4aD9d5H9bVWz+JcZvftPNCXHFcxmKlQmYiEoonkU=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=nrMgvjTQiW24jgTEn9nVCrQBKcdxUNzOADK7GdxSDy3abNOQ+r2W/3iiVPmu50xze HHlzBXLn5gI3V0o9TuUOhAHF0bqs42FA6vr5ylJnuIsneueM7MA13nr6fSW6euaPIP o4Y9OF7Cw2PC0UJikWim7xnga0PXhhZWnbu0vTVFQ9RSiopZDpAZR2JKZLPTmdK0eu iqDFnkEjBHfXhLuDm7NWX43SdCqrytkRDYxjHRM3wy4gZO+yOGnwFeE0fGj3aS31Js Dg9nwAoOIp/m7nYpu/wFMGgGcJqE3+d4tHtT53+qBEELZ7jaPfmlYz33EdIF11HqAr 68HqgYYfRsc/w== Date: Sat, 23 Nov 2024 19:47:24 +0100 From: Christian Brauner To: Linus Torvalds Cc: Amir Goldstein , Miklos Szeredi , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-unionfs@vger.kernel.org Subject: Re: [GIT PULL] overlayfs updates for 6.13 Message-ID: <20241123-wortreich-eistee-542b69311fba@brauner> References: <20241122095746.198762-1-amir73il@gmail.com> <20241123-bauhof-tischbein-579ff1db831a@brauner> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20241123-bauhof-tischbein-579ff1db831a@brauner> On Sat, Nov 23, 2024 at 01:06:14PM +0100, Christian Brauner wrote: > On Fri, Nov 22, 2024 at 09:21:58PM -0800, Linus Torvalds wrote: > > On Fri, 22 Nov 2024 at 01:57, Amir Goldstein wrote: > > > > > > - Introduction and use of revert/override_creds_light() helpers, that were > > > suggested by Christian as a mitigation to cache line bouncing and false > > > sharing of fields in overlayfs creator_cred long lived struct cred copy. > > > > So I don't actively hate this, but I do wonder if this shouldn't have > > been done differently. > > > > In particular, I suspect *most* users of override_creds() actually > > wants this "light" version, because they all already hold a ref to the > > cred that they want to use as the override. > > > > We did it that safe way with the extra refcount not because most > > people would need it, but it was expected to not be a big deal. > > > > Now you found that it *is* a big deal, and instead of just fixing the > > old interface, you create a whole new interface and the mental burden > > of having to know the difference between the two. > > > So may I ask that you look at perhaps just converting the (not very > > many) users of the non-light cred override to the "light" version? > > I think that could be a good idea in general. > > But I have to say I'm feeling a bit defensive after having read your > message even though I usually try not to. :) It was just pointed out to me that this was written like I'm not reading you messages - which is obviously not the case. What I means it that I usually try to not be defensive when valid criticism is brought up. :)