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Tue, 13 Oct 2026 08:16:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1791879396; bh=10xqpOPjo9d02qrdR+y1QjD6wm0apoWOTLYxCcvp86U=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=AqDbgD7RPDZnA8yWlYoCzTaFRLOEfIfXzuIMKlCL0epBr0Q3gbAfflTnYwIztLzRJ 1GIASb+SV5fm+Wt6MXY0BlSjWTWYgCjYU6cR5YuG0eJyHI69gxSY70lyorCsP211Xx 4ut57CQ/1zfAAnpUaD51OQclSZdWPg5JoTu35UR5W2wJc6escRvVEKOJwduD/6jILN ldUfK5O6TW3PM6fj3iL/ZkdIjm31vtT9H7502xcv3vCGKHJihsf9p7e1XMCwMX8bJh ide58ONFM3JIvdrsvoZbUry/Ff2H9kJrzppM1DZBNC88QSLZfn4gGrjOW0TL1fDahr PuPREpWrFOp7Q== Date: Tue, 13 Oct 2026 10:16:29 +0200 From: Gao Xiang To: Greg KH Cc: stable@vger.kernel.org, Sasha Levin , stable-commits@vger.kernel.org, xiang@kernel.org, Chao Yu , Yue Hu , Jeffle Xu , Sandeep Dhavale , Hongbo Li , Chunhai Guo , Jonathan Corbet , Shuah Khan , Randy Dunlap , linux-erofs@lists.ozlabs.org Subject: Re: Patch "erofs: remove fscache backend entirely" has been added to the 6.18-stable tree Message-ID: Mail-Followup-To: Greg KH , stable@vger.kernel.org, Sasha Levin , stable-commits@vger.kernel.org, xiang@kernel.org, Chao Yu , Yue Hu , Jeffle Xu , Sandeep Dhavale , Hongbo Li , Chunhai Guo , Jonathan Corbet , Shuah Khan , Randy Dunlap , linux-erofs@lists.ozlabs.org References: <20261013020044.2527207-1-sashal@kernel.org> <2026101352-subtract-deflector-a77b@gregkh> X-Mailing-List: linux-erofs@lists.ozlabs.org List-Id: List-Help: List-Owner: List-Post: List-Subscribe: , , List-Unsubscribe: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <2026101352-subtract-deflector-a77b@gregkh> Hi Greg, On Tue, Oct 13, 2026 at 09:59:58AM +0200, Greg KH wrote: > On Tue, Oct 13, 2026 at 09:28:44AM +0200, Gao Xiang wrote: > > Hi Sasha, > > > > I'm not sure why we need to backport this into stable kernels, as there > > are users who use EROFS over fscache on these stable kernels. > > > > The functionality works and it's a breaking change. Could you please > > kindly tell why? > > Why would you have a breaking change in Linus's tree? We never break > existing users, so how was this ever accepted in mainline? Because the similar + better functionality "erofs over fanotify" is already available in the recent upstream, and it has simpler interfaces than "erofs over fscache.", so we don't actually break users as long as one of those functionalities exist ("erofs over fanotify" or "erofs over fscache". Many stable kernels don't support "erofs over fsnotify", so backport this commit will make existing users using old stable kernels have no choice (no "erofs over fanotify" nor "erofs over fscache"). The commit message is already described well I think. > > As this removal fixes known bugs, isn't that a good thing for those > older users as well? Why would you want them to run broken systems? I think it depends on the importance of the bug, at least "erofs over fscache" is usable (and it's used by vendors) on stable kernels, but it's unneeded to address every edge case found by LLMs since I mostly think it doesn't impact the real use case, and as I said, we have a new unique interface ("erofs over fanotify") now, but only on very latest kernels. Also there could always be breaking changes for various reasons (e.g. obsolete/dispute filesystem breaking changes these years like bcachefs, etc), will these commits be backported to all stable kernels too? Thanks, Gao Xiang > > thanks, > > greg k-h >