From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from frasgout.his.huawei.com (frasgout.his.huawei.com [185.176.79.56]) (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 558663BC4FB; Tue, 20 Jan 2026 09:12:27 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=185.176.79.56 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768900350; cv=none; b=ncRvLpd5ckhN3NN6mWjfbqPG+S1x2IbDDTSR5SSA4SzgTP/t35hBfbMbiS/kAEM7neW50qdAKzhA/PsIgv8gkAz3UftMIZMwk62KLC1egYR+qYL8RjLG4Cq54QlHGeRxXj+/J9AboDn7NJoS1rB3vg/UHk17Cv7dn70T/ltW9/M= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768900350; c=relaxed/simple; bh=B05gVguD6HO3xQvzt2rGs+vO4e4DANFflmUfKhWSQPw=; h=Date:From:To:CC:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=hsV8UjvU7eZoV4gGPN1QsjJJUzVdQPFELTRzmEnOJ+Y2p3Tx87Bpvz1l0FBRoSW1+lB7dY6f9gZ/4eU3XVgnndEFSSTomoOre4rKrDavOtbZDbcbkccFNs+HNe5dcwFNX4ohja/TrX4LokkAaHoT3aTazURrYOM3DuV1Q6Wvx9c= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com; spf=pass smtp.mailfrom=huawei.com; arc=none smtp.client-ip=185.176.79.56 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=huawei.com Received: from mail.maildlp.com (unknown [172.18.224.107]) by frasgout.his.huawei.com (SkyGuard) with ESMTPS id 4dwM5j0FVBzHnH4v; Tue, 20 Jan 2026 17:11:53 +0800 (CST) Received: from dubpeml500005.china.huawei.com (unknown [7.214.145.207]) by mail.maildlp.com (Postfix) with ESMTPS id 7874640571; Tue, 20 Jan 2026 17:12:24 +0800 (CST) Received: from localhost (10.203.177.99) by dubpeml500005.china.huawei.com (7.214.145.207) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1544.11; Tue, 20 Jan 2026 09:12:22 +0000 Date: Tue, 20 Jan 2026 09:12:17 +0000 From: Alireza Sanaee To: John Groves CC: John Groves , Miklos Szeredi , "Dan Williams" , Bernd Schubert , Alison Schofield , John Groves , John Groves , Jonathan Corbet , Vishal Verma , Dave Jiang , Matthew Wilcox , Jan Kara , Alexander Viro , David Hildenbrand , Christian Brauner , "Darrick J . Wong" , Randy Dunlap , "Jeff Layton" , Amir Goldstein , "Jonathan Cameron" , Stefan Hajnoczi , Joanne Koong , Josef Bacik , Bagas Sanjaya , James Morse , Fuad Tabba , Sean Christopherson , Shivank Garg , Ackerley Tng , Gregory Price , Aravind Ramesh , Ajay Joshi , "venkataravis@micron.com" , "linux-doc@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "nvdimm@lists.linux.dev" , "linux-cxl@vger.kernel.org" , "linux-fsdevel@vger.kernel.org" Subject: Re: [PATCH BUNDLE v7] famfs: Fabric-Attached Memory File System Message-ID: <20260120091217.00007537.alireza.sanaee@huawei.com> In-Reply-To: <0100019bd33a16b4-6da11a99-d883-4cfc-b561-97973253bc4a-000000@email.amazonses.com> References: <20260118222911.92214-1-john@jagalactic.com> <0100019bd33a16b4-6da11a99-d883-4cfc-b561-97973253bc4a-000000@email.amazonses.com> Organization: Huawei X-Mailer: Claws Mail 4.3.0 (GTK 3.24.42; x86_64-w64-mingw32) 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-Transfer-Encoding: 7bit X-ClientProxiedBy: lhrpeml500010.china.huawei.com (7.191.174.240) To dubpeml500005.china.huawei.com (7.214.145.207) On Sun, 18 Jan 2026 22:29:18 +0000 John Groves wrote: Hi John, I wonder if these new patches sent recently have been reflected on the github repo readme files. It seems it is not, is it? > This is a coordinated patch submission for famfs (Fabric-Attached Memory > File System) across three repositories: > > 1. Linux kernel (cover + 19 patches) - dax fsdev driver + fuse/famfs > integration > 2. libfuse (cover + 3 patches) - famfs protocol support for fuse servers > 3. ndctl/daxctl (cover + 2 patches) - support for the new "famfs" devdax > mode > > Each series is posted as a reply to this cover message, with individual > patches replying to their respective series cover. > > Overview > -------- > Famfs exposes shared memory as a file system. It consumes shared memory > from dax devices and provides memory-mappable files that map directly to > the memory with no page cache involvement. Famfs differs from conventional > file systems in fs-dax mode in that it handles in-memory metadata in a > sharable way (which begins with never caching dirty shared metadata). > > Famfs started as a standalone file system [1,2], but the consensus at > LSFMM 2024 and 2025 [3,4] was that it should be ported into fuse. > > The key performance requirement is that famfs must resolve mapping faults > without upcalls. This is achieved by fully caching the file-to-devdax > metadata for all active files via two fuse client/server message/response > pairs: GET_FMAP and GET_DAXDEV. > > Patch Series Summary > -------------------- > > Linux Kernel (V7, 19 patches): > - dax: New fsdev driver (drivers/dax/fsdev.c) providing a devdax mode > compatible with fs-dax. Devices can be switched among 'devdax', 'fsdev' > and 'system-ram' modes via daxctl or sysfs. > - fuse: Famfs integration adding GET_FMAP and GET_DAXDEV messages for > caching file-to-dax mappings in the kernel. > > libfuse (V7, 3 patches): > - Updates fuse_kernel.h to kernel 6.19 baseline > - Adds famfs DAX fmap protocol definitions > - Implements famfs DAX fmap support for fuse servers > > ndctl/daxctl (V4, 2 patches): > - Adds daxctl support for the new "famfs" mode of devdax > - Adds test/daxctl-famfs.sh for testing mode transitions > > Changes Since V2 (kernel) > ------------------------- > - Dax: Completely new fsdev driver replaces the dev_dax_iomap modifications. > Uses MEMORY_DEVICE_FS_DAX type with order-0 folios for fs-dax compatibility. > - Dax: The "poisoned page" problem is properly fixed via fsdev_clear_folio_state() > which clears stale mapping/compound state when fsdev binds. > - Dax: Added dax_set_ops() and driver unbind protection while filesystem mounted. > - Fuse: Famfs mounts require CAP_SYS_RAWIO (exposing raw memory devices). > - Fuse: Added DAX address_space_operations with noop_dirty_folio. > - Rebased to latest kernels, compatible with recent dax refactoring. > > Testing > ------- > The famfs user space [5] includes comprehensive smoke and unit tests that > exercise all three components together. The ndctl series includes a > dedicated test for famfs mode transitions. > > References > ---------- > [1] https://lore.kernel.org/linux-cxl/cover.1708709155.git.john@groves.net/ > [2] https://lore.kernel.org/linux-cxl/cover.1714409084.git.john@groves.net/ > [3] https://lwn.net/Articles/983105/ (LSFMM 2024) > [4] https://lwn.net/Articles/1020170/ (LSFMM 2025) > [5] https://famfs.org (famfs user space) > [6] https://lore.kernel.org/linux-cxl/20250703185032.46568-1-john@groves.net/ (V2) > [7] https://lore.kernel.org/linux-fsdevel/20260107153244.64703-1-john@groves.net/T/#m0000d8c00290f48c086b8b176c7525e410f8508c (related ndctl series) > -- > John Groves > > >