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Re: d_off field in struct dirent and 32-on-64 emulation
- From: Florian Weimer <fw at deneb dot enyo dot de>
- To: Adhemerval Zanella <adhemerval dot zanella at linaro dot org>
- Cc: linux-fsdevel at vger dot kernel dot org, linux-api at vger dot kernel dot org, linux-ext4 at vger dot kernel dot org, linux-kernel at vger dot kernel dot org, v9fs-developer at lists dot sourceforge dot net, libc-alpha at sourceware dot org, qemu-devel at nongnu dot org, ericvh at gmail dot com, rminnich at sandia dot gov, lucho at ionkov dot net, hpa at zytor dot com, arnd at arndb dot de
- Date: Thu, 27 Dec 2018 19:09:11 +0100
- Subject: Re: d_off field in struct dirent and 32-on-64 emulation
- References: <87bm56vqg4.fsf@mid.deneb.enyo.de> <957967d7-5717-8ada-fb30-dfdf19898b6b@linaro.org>
* 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:
>> There is another annoying aspect: The standards expose d_off through
>> the telldir function, and that returns long int on all architectures
>> (not off_t, so unchanged by _FILE_OFFSET_BITS). That's mostly a
>> userspace issue and thus needing different steps to resolve (possibly
>> standards action).