linux-kernel - Re: [PATCH] mm: add prototype for __add_to_page_cache

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Message-ID: <CAADnVQ+DStjXJPUbUL7ggXyFj_iJuNDB56jdhzsq=D=QxgQQXg@mail.gmail.com>
Date:   Sun, 27 Dec 2020 16:59:24 -0800
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     Christoph Hellwig <hch@...radead.org>
Cc:     Matthew Wilcox <willy@...radead.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Souptick Joarder <jrdr.linux@...il.com>,
        linux-mm <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Alex Shi <alex.shi@...ux.alibaba.com>
Subject: Re: [PATCH] mm: add prototype for __add_to_page_cache_locked()

On Wed, Dec 23, 2020 at 7:54 AM Christoph Hellwig <hch@...radead.org> wrote:
>
> On Wed, Dec 23, 2020 at 12:11:36PM +0000, Matthew Wilcox wrote:
> > On Wed, Dec 23, 2020 at 08:31:26AM +0000, Christoph Hellwig wrote:
> > > Can we please make the eBPF code stop referencing this function instead
> > > of papering over this crap?  It has no business poking into page cache
> > > internals.
> >
> > The reference from the BPF code is simply "you can inject errors here".
> > And I think we want to be able to inject errors to test the error paths,
> > no?
>
> Something that expects a symbol to be global is just pretty broken.
> I think it need to change so that whatever instrumentation is done can
> coexist with a static function.

Pls read commit description that made it global.
It has nothing to do with bpf.