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 725542BEC43; Thu, 13 Nov 2025 17:00:02 +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=1763053202; cv=none; b=MOLfMiT2caJbS9f7jZpngBFbl7g94Ru5WvKRLwOql8J6CodN5fJurXJeuBxezSJ3H8t6RGp6gFzY0BFvnVpdFC5pm9oDtmzifvHkOGDn0K42P8TGGtONxP2P4+uThmuFCvwDZvCrzW0UrNkF08WNzPuhgyPp9zCVRL9BdQGcubU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763053202; c=relaxed/simple; bh=OBpr4OfEynmd3QPtz7HpqQa1JuoHzfmsOcTyDkjnDvg=; h=From:To:Cc:Subject:In-Reply-To:References:Date:Message-ID: MIME-Version:Content-Type; b=l9Ov5qE+FPKQaax6Jx7AhaAuMcfk/2+2wr2criXPHMccPQQCkfimg+aIPN9+TjbWWL1ZVKK5uH77X3c+Q0d4QYx3lgOrOdI0XTWHe4NC9Jm5j4TeF/CXb/BPYgHKslciWyu0m1H9hlY/Vv2GQ3F6j22gL62pNLYMkvTUSDSeJnk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=GKpbgHVA; 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="GKpbgHVA" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7A7DAC4CEF5; Thu, 13 Nov 2025 16:59:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1763053202; bh=OBpr4OfEynmd3QPtz7HpqQa1JuoHzfmsOcTyDkjnDvg=; h=From:To:Cc:Subject:In-Reply-To:References:Date:From; b=GKpbgHVAB96CTF2QAU6gGXB9xyAtOYn7EP9js0Mycon0OeXhF2jqHHtX89c5XmG3n aI+GsuLi5aWWIqQuOeufUD4aA/2oqU4CL3hOKgWLJISLTlCDKD2fvEzTYvo+4axv1Y RMC80Z36Upuv7S76Aj7akkAJYpehDBHHl02KtLD9+owbFDV5HjZtX2uU4oNhmImcTZ TB6NozxahkQlkcbHdVJIiuprn3ewx0G92tYj/3ivDFDMjJkdV5nEmpt/dhUVJduyaG M6PpSxx1REjCjMlgwB+uTMHEl+k2ror8Zzap/3OLPhR5zcZpm4wrMVCWSYXfzyE61t +lyMXl3tACR7w== From: Pratyush Yadav To: Pasha Tatashin Cc: pratyush@kernel.org, jasonmiu@google.com, graf@amazon.com, rppt@kernel.org, dmatlack@google.com, rientjes@google.com, corbet@lwn.net, rdunlap@infradead.org, ilpo.jarvinen@linux.intel.com, kanie@linux.alibaba.com, ojeda@kernel.org, aliceryhl@google.com, masahiroy@kernel.org, akpm@linux-foundation.org, tj@kernel.org, yoann.congal@smile.fr, mmaurer@google.com, roman.gushchin@linux.dev, chenridong@huawei.com, axboe@kernel.dk, mark.rutland@arm.com, jannh@google.com, vincent.guittot@linaro.org, hannes@cmpxchg.org, dan.j.williams@intel.com, david@redhat.com, joel.granados@kernel.org, rostedt@goodmis.org, anna.schumaker@oracle.com, song@kernel.org, zhangguopeng@kylinos.cn, linux@weissschuh.net, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-mm@kvack.org, gregkh@linuxfoundation.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com, rafael@kernel.org, dakr@kernel.org, bartosz.golaszewski@linaro.org, cw00.choi@samsung.com, myungjoo.ham@samsung.com, yesanishhere@gmail.com, Jonathan.Cameron@huawei.com, quic_zijuhu@quicinc.com, aleksander.lobakin@intel.com, ira.weiny@intel.com, andriy.shevchenko@linux.intel.com, leon@kernel.org, lukas@wunner.de, bhelgaas@google.com, wagi@kernel.org, djeffery@redhat.com, stuart.w.hayes@gmail.com, lennart@poettering.net, brauner@kernel.org, linux-api@vger.kernel.org, linux-fsdevel@vger.kernel.org, saeedm@nvidia.com, ajayachandra@nvidia.com, jgg@nvidia.com, parav@nvidia.com, leonro@nvidia.com, witu@nvidia.com, hughd@google.com, skhawaja@google.com, chrisl@kernel.org Subject: Re: [PATCH v5 18/22] docs: add documentation for memfd preservation via LUO In-Reply-To: (Pasha Tatashin's message of "Thu, 13 Nov 2025 11:55:25 -0500") References: <20251107210526.257742-1-pasha.tatashin@soleen.com> <20251107210526.257742-19-pasha.tatashin@soleen.com> Date: Thu, 13 Nov 2025 17:59:51 +0100 Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) Precedence: bulk X-Mailing-List: linux-api@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain On Thu, Nov 13 2025, Pasha Tatashin wrote: >> +Limitations >> +=========== >> + >> +The current implementation has the following limitations: >> + >> +Size >> + Currently the size of the file is limited by the size of the FDT. The FDT can >> + be at of most ``MAX_PAGE_ORDER`` order. By default this is 4 MiB with 4K >> + pages. Each page in the file is tracked using 16 bytes. This limits the >> + maximum size of the file to 1 GiB. > > The above should be removed, as we are using KHO vmalloc that resolves > this limitation. Pratyush, I suggest for v6 let's move memfd > documnetation right into the code: memfd_luo.c and > liveupdate/abi/memfd.h, and source it from there. ACK. I think the section on behavior in different phases is also out of date now, and the serialization format too. The format is more accurately defined in include/linux/liveupdate/abi/memfd.h. So this documentation needs an overhaul. I don't mind moving it to the code and including it in the HTML docs via kernel-doc. Will do that for the next revision. > > Keeping documentation with the code helps reduce code/doc divergence. > > Pasha -- Regards, Pratyush Yadav