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 8BD9221FF46; Mon, 7 Jul 2025 17:32:25 +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=1751909545; cv=none; b=lI6BLgJPxxDNha8+LwgKfCk7zfTkY44s/JGbbEWsdRDDcW2W1UhCV2PC6J+ebi1YqQMFb/OcgvvHsBvbpSdT7c85W+/CtGzddIcZz3R4WzZuepk0FHLKYGTtAhZeBYeM+R1Jg4kG1/F/caZ2UlEYC1L0SrWC8NnGGqBghQUwvWo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1751909545; c=relaxed/simple; bh=WVJM3SZSm3oQSvOHm5Mfdm6shiB97KhB2K1EJcyPlbo=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=BVBYNje2MSN6nZ27ISEHaEG+Zl/CTQpYddOQL3FDFiJ6n+gzaE9hL5IDLCCyIzMuBMqF1dow5bAl4WyMRqbCoGom52r/Bl73pXnTvqxcU/AMPc16A+y7TPj8CtovKl9oGibItVwA+iF4pl49zVlYL7v4DTDWOGFMzyVZRxrsjWc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=TOGbFC3j; 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="TOGbFC3j" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 08608C4CEE3; Mon, 7 Jul 2025 17:32:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1751909545; bh=WVJM3SZSm3oQSvOHm5Mfdm6shiB97KhB2K1EJcyPlbo=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=TOGbFC3ja6kH0v9HVh6u72McOgfluLSdOzEl0TSfObx4qj05LTIsPZp1YlFp2d/KG jcTh6/TPj2VgfH9UGVMW6K6F49OGVGdMj5DwDN3M35DFbdPHkdwuTBEr+71QgI3QU+ C5vqjR/EQXTveC357KTHMSU71XAs1IhWyXz8GmlfXVqeLtICIFll0Tq7M0SDuVYKFP M6DERATRLZxQAFTwmNEta7o/v3ZVuPFxv+4odjv9O9cGxAkvPPRhphawIC4Y3mvNWT nIS+i970xaZT9HLpaJR/52GJ7VN7wxQ3nsDnG8QJqGrnaFxTMtkk49iKldeDEqzm/h 49110wloNqfGQ== Date: Mon, 7 Jul 2025 10:32:24 -0700 From: "Darrick J. Wong" To: John Groves Cc: Dan Williams , Miklos Szeredi , Bernd Schubert , John Groves , Jonathan Corbet , Vishal Verma , Dave Jiang , Matthew Wilcox , Jan Kara , Alexander Viro , Christian Brauner , Randy Dunlap , Jeff Layton , Kent Overstreet , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, nvdimm@lists.linux.dev, linux-cxl@vger.kernel.org, linux-fsdevel@vger.kernel.org, Amir Goldstein , Jonathan Cameron , Stefan Hajnoczi , Joanne Koong , Josef Bacik , Aravind Ramesh , Ajay Joshi Subject: Re: [RFC V2 10/18] famfs_fuse: Basic fuse kernel ABI enablement for famfs Message-ID: <20250707173224.GB2672029@frogsfrogsfrogs> References: <20250703185032.46568-1-john@groves.net> <20250703185032.46568-11-john@groves.net> Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Thu, Jul 03, 2025 at 05:45:48PM -0500, John Groves wrote: > On 25/07/03 01:50PM, John Groves wrote: > > * FUSE_DAX_FMAP flag in INIT request/reply > > > > * fuse_conn->famfs_iomap (enable famfs-mapped files) to denote a > > famfs-enabled connection > > > > Signed-off-by: John Groves > > --- > > fs/fuse/fuse_i.h | 3 +++ > > fs/fuse/inode.c | 14 ++++++++++++++ > > include/uapi/linux/fuse.h | 4 ++++ > > 3 files changed, 21 insertions(+) > > > > diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h > > index 9d87ac48d724..a592c1002861 100644 > > --- a/fs/fuse/fuse_i.h > > +++ b/fs/fuse/fuse_i.h > > @@ -873,6 +873,9 @@ struct fuse_conn { > > /* Use io_uring for communication */ > > unsigned int io_uring; > > > > + /* dev_dax_iomap support for famfs */ > > + unsigned int famfs_iomap:1; > > + > > /** Maximum stack depth for passthrough backing files */ > > int max_stack_depth; > > > > diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c > > index 29147657a99f..e48e11c3f9f3 100644 > > --- a/fs/fuse/inode.c > > +++ b/fs/fuse/inode.c > > @@ -1392,6 +1392,18 @@ static void process_init_reply(struct fuse_mount *fm, struct fuse_args *args, > > } > > if (flags & FUSE_OVER_IO_URING && fuse_uring_enabled()) > > fc->io_uring = 1; > > + if (IS_ENABLED(CONFIG_FUSE_FAMFS_DAX) && > > + flags & FUSE_DAX_FMAP) { > > + /* XXX: Should also check that fuse server > > + * has CAP_SYS_RAWIO and/or CAP_SYS_ADMIN, > > + * since it is directing the kernel to access > > + * dax memory directly - but this function > > + * appears not to be called in fuse server > > + * process context (b/c even if it drops > > + * those capabilities, they are held here). > > + */ > > + fc->famfs_iomap = 1; > > I think there should be a check here that the fuse server is > capable(CAP_SYS_RAWIO) (or maybe CAP_SYS_ADMIN), but this function doesn't > run in fuse server context. A famfs fuse server is providing fmaps, which > map files to devdax memory, which should not be an unprivileged operation. I thought process_init_reply /does/ run in the fuse server's context. It calls process_init_limits, which checks for capable(CAP_SYS_ADMIN)... --D > 1) Does fs/fuse already store the capabilities of the fuse server? > 2) If not, where do you suggest I do that, and where do you suggest I store > that info? The only dead-obvious place (to me) that fs/fuse runs in server > context is in fuse_dev_open(), but it doesn't store anything... > > @Miklos, I'd appreciate your advice here. > > Thanks! > John > >