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From: Miklos Szeredi <miklos@szeredi.hu>
Date: Wed, 7 Feb 2024 10:54:34 +0100
Message-ID: <CAJfpegtw0-88qLjy0QDLyYFZEM7PJCG3R-mBMa9s8TNSVZmJTA@mail.gmail.com>
Subject: [LSF/MM/BPF TOPIC] tracing the source of errors
To: lsf-pc <lsf-pc@lists.linux-foundation.org>
Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org
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[I'm not planning to attend LSF this year, but I thought this topic
might be of interest to those who will.]

The errno thing is really ancient and yet quite usable.  But when
trying to find out where a particular EINVAL is coming from, that's
often mission impossible.

Would it make sense to add infrastructure to allow tracing the source
of errors?  E.g.

strace --errno-trace ls -l foo
..
statx(AT_FDCWD, "foo", ...) = -1 ENOENT [fs/namei.c:1852]
..

Don't know about others, but this issue comes up quite often for me.

I would implement this with macros that record the place where a
particular error has originated, and some way to query the last one
(which wouldn't be 100% accurate, but good enough I guess).

Thanks,
Miklos