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Date:   Tue, 6 Aug 2019 15:42:33 -0700
From:   Andrew Morton <akpm@linux-foundation.org>
To:     NeilBrown <neilb@suse.com>
Cc:     Alexander Viro <viro@zeniv.linux.org.uk>,
        Sergei Turchanov <turchanov@farpost.com>,
        linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] seq_file: fix problem when seeking mid-record.
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On Mon, 05 Aug 2019 14:26:08 +1000 NeilBrown <neilb@suse.com> wrote:

> If you use lseek or similar (e.g. pread) to access
> a location in a seq_file file that is within a record,
> rather than at a record boundary, then the first read
> will return the remainder of the record, and the second
> read will return the whole of that same record (instead
> of the next record).
> Whnn seeking to a record boundary, the next record is
> correctly returned.

ouch.  I'm surprised it took this long to be noticed.

Maybe we need a seqfile-basher in tools/testing/selftests/proc or
somewhere.