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

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Message-ID: <20201223155254.GA6138@infradead.org>
Date:   Wed, 23 Dec 2020 15:52:54 +0000
From:   Christoph Hellwig <hch@...radead.org>
To:     Matthew Wilcox <willy@...radead.org>
Cc:     Christoph Hellwig <hch@...radead.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Souptick Joarder <jrdr.linux@...il.com>, linux-mm@...ck.org,
        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 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.