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 9BA5DD2EC; Sat, 23 Dec 2023 13:04:39 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="C6qgc1pO" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0C06FC433C7; Sat, 23 Dec 2023 13:04:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1703336679; bh=pSQbXnxiyqNqmbq5Ho7XxCP4UcVUyAZ8MoVPSyk4+z0=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=C6qgc1pOwX7mfGWLVLcYJx+6peuoQfiZcxbmU76QVYG0g2xp+OYkFq3X0iwIT+5Co CXyGWMNvlkgUv3KQ4LB5WCKIFtJjemhvLbMvHL3m15C+JnyvdMoPPHK4Wd24Oiyqh6 B4mSFPbV994esq8xk7OEv/wk6RFcxiH3HCTmz2Da5S7cS/rwwTcSk53W6XWyxVkRdr KCQGxEJk4Fy6rv/jly1eU0HscCKwIwosA/onP53at2sP7mjTf8ec5n8zB31G2TO/mS Xvn+K9RckaFunpU2GHC1SOKX6T8vhBhTWLWByxBiakAd3UQmxIMiFWc0wDlcxt2jrE JBq6U0n0XbZmQ== Date: Sat, 23 Dec 2023 14:04:35 +0100 From: Christian Brauner To: Amir Goldstein Cc: Miklos Szeredi , linux-fsdevel@vger.kernel.org, linux-unionfs@vger.kernel.org Subject: Re: [RFC][PATCH 4/4] fs: factor out backing_file_mmap() helper Message-ID: <20231223-zerlegen-eidesstattlich-a1f309e30dbc@brauner> References: <20231221095410.801061-1-amir73il@gmail.com> <20231221095410.801061-5-amir73il@gmail.com> <20231222-gespeichert-prall-3183a634baae@brauner> Precedence: bulk X-Mailing-List: linux-unionfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: On Sat, Dec 23, 2023 at 08:56:08AM +0200, Amir Goldstein wrote: > On Sat, Dec 23, 2023 at 8:54 AM Amir Goldstein wrote: > > > > On Fri, Dec 22, 2023 at 2:54 PM Christian Brauner wrote: > > > > > > On Thu, Dec 21, 2023 at 11:54:10AM +0200, Amir Goldstein wrote: > > > > Assert that the file object is allocated in a backing_file container > > > > so that file_user_path() could be used to display the user path and > > > > not the backing file's path in /proc//maps. > > > > > > > > Signed-off-by: Amir Goldstein > > > > --- > > > > fs/backing-file.c | 27 +++++++++++++++++++++++++++ > > > > fs/overlayfs/file.c | 23 ++++++----------------- > > > > include/linux/backing-file.h | 2 ++ > > > > 3 files changed, 35 insertions(+), 17 deletions(-) > > > > > > > > diff --git a/fs/backing-file.c b/fs/backing-file.c > > > > index 46488de821a2..1ad8c252ec8d 100644 > > > > --- a/fs/backing-file.c > > > > +++ b/fs/backing-file.c > > > > @@ -11,6 +11,7 @@ > > > > #include > > > > #include > > > > #include > > > > +#include > > > > > > > > #include "internal.h" > > > > > > > > @@ -284,6 +285,32 @@ ssize_t backing_file_splice_write(struct pipe_inode_info *pipe, > > > > } > > > > EXPORT_SYMBOL_GPL(backing_file_splice_write); > > > > > > > > +int backing_file_mmap(struct file *file, struct vm_area_struct *vma, > > > > + struct backing_file_ctx *ctx) > > > > +{ > > > > + const struct cred *old_cred; > > > > + int ret; > > > > + > > > > + if (WARN_ON_ONCE(!(file->f_mode & FMODE_BACKING)) || > > > > > > Couldn't that WARN_ON_ONCE() be in every one of these helpers in this > > > series? IOW, when would you ever want to use a backing_file_*() helper > > > on a non-backing file? > > > > AFAIK, the call chain below backing_file_splice*() and backing_file_*_iter() > > helpers never end up accessing file_user_path() or assuming that fd of file > > is installed in fd table, so there is no strong reason to enforce this with an > > assertion. Yeah, but you do use an override_cred() call and you do have that backing_file_ctx. It smells like a bug if anyone would pass in a non-backing file. > > > > We can do it for clarity of semantics, in case one of the call chains will > > start assuming a struct backing_file in the future. WDIT? > > Doh! WDYT? I'd add it as the whole series is predicated on this being used for backing files.