From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Michael Kerrisk (man-pages)" Subject: Re: [patch] posix_fallocate.3: Mention glibc emulation caveats. Date: Thu, 08 Oct 2015 23:10:18 +0200 Message-ID: <5616DBBA.2080906@gmail.com> References: <560E0567.7040204@redhat.com> <56123D86.9050601@gmail.com> <561521D6.50106@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <561521D6.50106-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> Sender: linux-man-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Carlos O'Donell Cc: mtk.manpages-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org, "linux-man-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , GNU C Library List-Id: linux-man@vger.kernel.org On 10/07/2015 02:44 PM, Carlos O'Donell wrote: > On 10/05/2015 05:06 AM, Michael Kerrisk (man-pages) wrote: >> Hi Carlos, >> >> On 10/02/2015 05:17 AM, Carlos O'Donell wrote: >>> Michael, >>> >>> You're going to really enjoy reading this patch ;-) >> >> Thanks for the patch. What a sad story :-{ > > I've gotten at least one hate mail for documenting how broken > it is when the underlying filesystem doesn't support it ;-) > > Florian Weimer (Red Hat) started a rather long and interesting > discussion on libc-alpha about removing the emulation layer, > but we found that it was impossible to do without breaking a > lot of userspace applications that operate over NFS, are > single-threaded, and expect posix_fallocate to work correctly. > > The best compromise was to document the behaviour, and wait > for everyone to use NFS 4.2, at which point the issue goes > away. Until then we need to help users cope. > > The worst case scenario would be that we remove the fallback > and all the downstream users start implementing their own > incorrect and poorly tested fallback. One fallback > in one project, reviewed by a dozen people is sane. >> Thanks. I've applied. I tweaked the wording a bit in a further >> commit, and then made a further commit where I tried to fine tune >> the technical details a little. Could you please check commit >> 624fbe44d9c1ef54eb3fd36328f59a5037b87986 and let me know if there >> ia any technical misstep there? > > Looks perfect. The goal is to scare you into reviewing your code ;-) Thanks for checking it, Carlos. Cheers, Michael -- Michael Kerrisk Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/ Linux/UNIX System Programming Training: http://man7.org/training/ -- To unsubscribe from this list: send the line "unsubscribe linux-man" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html