From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from userp2120.oracle.com ([156.151.31.85]:32806 "EHLO userp2120.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753934AbdLUQqL (ORCPT ); Thu, 21 Dec 2017 11:46:11 -0500 Date: Thu, 21 Dec 2017 08:45:35 -0800 From: "Darrick J. Wong" Subject: Re: [ZOMG RFCRAP PATCH 0/2] xfs: horrifying eBPF hacks Message-ID: <20171221164535.GS12613@magnolia> References: <20171213061825.GO19219@magnolia> <20171221133338.GD1567@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20171221133338.GD1567@infradead.org> Sender: linux-xfs-owner@vger.kernel.org List-ID: List-Id: xfs To: Christoph Hellwig Cc: linux-xfs@vger.kernel.org, Richard Wareing , david@fromorbit.com On Thu, Dec 21, 2017 at 05:33:38AM -0800, Christoph Hellwig wrote: > Eek. Whie eBPF is a really nice debug tool we should never use > it for actual required kernel I/O functionality. Certainly not in its current hacky form. I'm curious if Richard has had a chance to try out these patches to see if it affects performance in a noticeable way? I /think/ bpf has enough safety mechanisms (no loops, no direct writing to kernel memory, bytecode verifiers, opcode count limits) that such a beast could be hidden behind a kconfig option that isn't turned for the general public. For people who have these particularly specific use cases I think it better to have a general mechanism to accomodate them vs. scattering code all over xfs vs. "no sorry go away", though this ebpf thing isn't necessarily the final answer. We do validate that the proposed iflags are allowed for the fs geometry, though I acknowledge that the prospect of running ebpf with ilock_excl does give me pause. I'm curious, though, what are your (and everyone else's) concerns about this? --D > -- > To unsubscribe from this list: send the line "unsubscribe linux-xfs" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html