From: Christian Brauner <christian.brauner@ubuntu.com>
To: Aleksa Sarai <cyphar@cyphar.com>
Cc: David Howells <dhowells@redhat.com>,
linux-api@vger.kernel.org, viro@zeniv.linux.org.uk,
metze@samba.org, torvalds@linux-foundation.org,
linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
fweimer@redhat.com
Subject: Re: Have RESOLVE_* flags superseded AT_* flags for new syscalls?
Date: Sun, 1 Mar 2020 17:46:34 +0100 [thread overview]
Message-ID: <20200301164634.ei4ayiipugp3bji4@wittgenstein> (raw)
In-Reply-To: <20200229155411.3xn7szvqso4uxwuy@yavin>
On Sun, Mar 01, 2020 at 02:54:11AM +1100, Aleksa Sarai wrote:
> On 2020-03-01, Aleksa Sarai <cyphar@cyphar.com> wrote:
> > On 2020-02-28, Christian Brauner <christian.brauner@ubuntu.com> wrote:
> > > So we either end up adding new AT_* flags mirroring the new RESOLVE_*
> > > flags or we end up adding new RESOLVE_* flags mirroring parts of AT_*
> > > flags. And if that's a possibility I vote for RESOLVE_* flags going
> > > forward. The have better naming too imho.
> >
> > I can see the argument for merging AT_ flags into RESOLVE_ flags (fewer
> > flag arguments for syscalls is usually a good thing) ... but I don't
> > really like it. There are a couple of problems right off the bat:
> >
> > * The prefix RESOLVE_ implies that the flag is specifically about path
> > resolution. While you could argue that AT_EMPTY_PATH is at least
> > *related* to path resolution, flags like AT_REMOVEDIR and
> > AT_RECURSIVE aren't.
> >
> > * That point touches on something I see as a more fundamental problem
> > in the AT_ flags -- they were intended to be generic flags for all of
> > the ...at(2) syscalls. But then AT_ grew things like AT_STATX_ and
> > AT_REMOVEDIR (both of which are necessary features to have for their
> > respective syscalls, but now those flag bits are dead for other
> > syscalls -- not to mention the whole AT_SYMLINK_{NO,}FOLLOW thing).
> >
> > * While the above might be seen as minor quibbles, the really big
> > issue is that even the flags which are "similar" (AT_SYMLINK_NOFOLLOW
> > and RESOLVE_NO_SYMLINKS) have different semantics (by design -- in my
> > view, AT_SYMLINK_{NO,}FOLLOW / O_NOFOLLOW / lstat(2) has always had
> > the wrong semantics if the intention was to be a way to safely avoid
> > resolving symlinks).
> >
> > But maybe I'm just overthinking what a merge of AT_ and RESOLVE_ would
> > look like -- would it on.
>
> Eugh, dropped the rest of that sentence:
>
> ... would it only be the few AT_ flags which are strictly related to
> path resolution (such as AT_EMPTY_PATH)? If so wouldn't that just mean
> we end up with two flag arguments for new syscalls?
That's a good question that we kinda ran into right once we
accepted the RESOLVE_* namespace implicitly? This smells like the same
problem we have in e.g. waitid() with WEXITED/WSTOPPED/WCONTINUED and
WNOHANG/WNOWAIT...I think one answer could be one flag argument,
different prefixes? i.e. RESOLVE_* and then e.g. simply REMOVE_DIR instead of
AT_REMOVEDIR. This way we don't duplicate the problem the AT_*
namespace had (e.g. AT_REMOVEDIR and AT_SYMLINK_NOFOLLOW being about two
separate things). Maybe that's crazy and doesn't really make things
better?
Christian
next prev parent reply other threads:[~2020-03-01 16:46 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-28 14:53 Have RESOLVE_* flags superseded AT_* flags for new syscalls? David Howells
2020-02-28 15:24 ` Christian Brauner
2020-02-29 15:26 ` Aleksa Sarai
2020-02-29 15:54 ` Aleksa Sarai
2020-03-01 16:46 ` Christian Brauner [this message]
2020-03-01 16:38 ` Christian Brauner
2020-03-02 11:30 ` Florian Weimer
2020-03-02 11:52 ` Christian Brauner
2020-03-02 12:05 ` Christian Brauner
2020-03-02 15:10 ` Christian Brauner
2020-03-02 15:36 ` Aleksa Sarai
2020-03-02 16:31 ` Christian Brauner
2020-03-02 12:09 ` Florian Weimer
2020-03-02 12:19 ` Christian Brauner
2020-03-02 12:35 ` Christian Brauner
2020-03-02 12:42 ` Florian Weimer
2020-03-02 12:55 ` Christian Brauner
[not found] ` <20200305141154.e246swv62rnctite@yavin>
2020-03-05 15:23 ` Christian Brauner
2020-03-05 14:33 ` David Howells
2020-03-05 14:38 ` Florian Weimer
2020-03-05 14:43 ` David Howells
2020-03-02 14:27 ` David Howells
2020-03-02 14:35 ` Christian Brauner
2020-03-02 14:50 ` David Howells
2020-03-02 15:05 ` Christian Brauner
2020-03-02 15:24 ` Aleksa Sarai
2020-03-02 16:37 ` David Howells
2020-03-06 14:48 ` David Howells
2020-03-02 15:10 ` Aleksa Sarai
2020-03-02 15:23 ` David Howells
2020-03-02 14:30 ` David Howells
2020-03-02 15:04 ` Aleksa Sarai
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