linux-kernel - Re: statx(2) API and documentation

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Message-ID: <87sh13ya8m.fsf@mid.deneb.enyo.de>
Date:   Thu, 18 Oct 2018 09:39:21 +0200
From:   Florian Weimer <fw@...eb.enyo.de>
To:     Miklos Szeredi <miklos@...redi.hu>
Cc:     Andreas Dilger <adilger@...ger.ca>,
        Michael Kerrisk <mtk.manpages@...il.com>,
        David Howells <dhowells@...hat.com>,
        Linux FS-devel Mailing List <linux-fsdevel@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux API <linux-api@...r.kernel.org>
Subject: Re: statx(2) API and documentation

* Miklos Szeredi:

> On Thu, Oct 18, 2018 at 12:22 AM, Florian Weimer <fw@...eb.enyo.de> wrote:
>> * Andreas Dilger:
>>
>>>> So what's the point exactly?
>>>
>>> Ah, I see your point...  STATX_ALL seems to be mostly useful for the kernel
>>> to mask off flags that it doesn't currently understand.  It doesn't make
>>> much sense for applications to specify STATX_ALL, since they don't have any
>>> way to know what each flag means unless they are hard-coded to check each of
>>> the STATX_* flags individually.  They should build up a mask of STATX_* flags
>>> based on what they care about (e.g. "find" should only request attributes
>>> based on the command-line options given).
>>
>> Could you remove it from the UAPI header?  I didn't want to put it
>> into the glibc header, but was overruled.
>
> To summarize Linus' rule of backward incompatibility: you can do it as
> long as nobody notices.  So yeah, we could try removing STATX_ALL from
> the uapi header, but we'd have to put it back in, once somebody
> complains.

I don't recall a rule about backwards-incompatible API changes.  This
wouldn't impact ABI at all.