From mboxrd@z Thu Jan 1 00:00:00 1970 From: Adhemerval Zanella Subject: Re: d_off field in struct dirent and 32-on-64 emulation Date: Fri, 28 Dec 2018 10:21:03 -0200 Message-ID: <4ee7419d-6537-8683-bf40-175cbdc6b484@linaro.org> References: <87bm56vqg4.fsf@mid.deneb.enyo.de> <957967d7-5717-8ada-fb30-dfdf19898b6b@linaro.org> <87pntmu9iw.fsf@mid.deneb.enyo.de> <87k1jtvp8u.fsf@mid.deneb.enyo.de> <87ftuhvp08.fsf@mid.deneb.enyo.de> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Return-path: In-Reply-To: <87ftuhvp08.fsf@mid.deneb.enyo.de> Content-Language: en-GB Sender: linux-kernel-owner@vger.kernel.org To: Florian Weimer Cc: linux-fsdevel@vger.kernel.org, linux-api@vger.kernel.org, linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org, v9fs-developer@lists.sourceforge.net, libc-alpha@sourceware.org, qemu-devel@nongnu.org, ericvh@gmail.com, lucho@ionkov.net, hpa@zytor.com, arnd@arndb.de List-Id: linux-api@vger.kernel.org On 28/12/2018 10:01, Florian Weimer wrote: > * Florian Weimer: > >> * Adhemerval Zanella: >> >>> On 27/12/2018 16:09, Florian Weimer wrote: >>>> * Adhemerval Zanella: >>>> >>>>> Also for glibc standpoint, although reverting it back to use getdents >>>>> syscall for non-LFS mode might fix this issue for architectures that >>>>> provides non-LFS getdents syscall it won't be a fix for architectures >>>>> that still provides off_t different than off64_t *and* only provides >>>>> getdents64 syscall. >>>>> >>>>> Currently we only have nios2 and csky (unfortunately). But since generic >>>>> definition for off_t and off64_t still assumes non-LFS support, all new >>>>> 32-bits ports potentially might carry the issue. >>>> >>>> For csky, we could still change the type of the non-standard d_off >>>> field to long long int. This way, only telldir would have to fail >>>> when truncation is necessary, as mentioned below: >>> >>> I think it makes no sense to continue making non-LFS as default for >>> newer 32 bits ports, the support will be emulated with LFS syscalls. >> >> Sorry, I don't see how this matters. seekdir and telldir are NOT >> affected by LFS. > > Ah, right. If struct dirent is 64-bit only, then the d_off member > will be 64 bits as well. But it is unclear whether you can use that > with lseek (probably yes, in its 64-bit variant), and it's unlikely > it's going to work with seekdir because of the POSIX-required long int > type. > I was referring to all other API that uses off_t as well (pread for instance), where new ports will have non-LFS variants that will call only LFS variants.