From: Alexei Starovoitov <alexei.starovoitov@gmail.com>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: Christoph Hellwig <hch@infradead.org>,
Stanislaw Gruszka <stf_xl@wp.pl>,
Matthew Wilcox <willy@infradead.org>,
Michal Kubecek <mkubecek@suse.cz>,
Justin Forbes <jmforbes@linuxtx.org>, bpf <bpf@vger.kernel.org>,
Alex Shi <alex.shi@linux.alibaba.com>,
Andrew Morton <akpm@linux-foundation.org>,
Souptick Joarder <jrdr.linux@gmail.com>,
Linux-MM <linux-mm@kvack.org>,
LKML <linux-kernel@vger.kernel.org>,
Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Josef Bacik <josef@toxicpanda.com>
Subject: Re: [PATCH] mm/filemap: add static for function __add_to_page_cache_locked
Date: Wed, 9 Dec 2020 19:02:11 -0800 [thread overview]
Message-ID: <CAADnVQ+6n4Nf5TczYWqLBrYJF_fEmRVyEbGqmaT0G9XoS7iMxA@mail.gmail.com> (raw)
In-Reply-To: <20201209213126.79ca1326@oasis.local.home>
On Wed, Dec 9, 2020 at 6:31 PM Steven Rostedt <rostedt@goodmis.org> wrote:
>
> On Wed, 9 Dec 2020 17:12:43 -0800
> Alexei Starovoitov <alexei.starovoitov@gmail.com> wrote:
>
> > > > > > FWIW, I intend to do some consolidation/renaming in this area. I
> > > > > > trust that will not be a problem?
> > > > >
> > > > > If it does not break anything, it will be not a problem ;-)
> > > > >
> > > > > It's possible that __add_to_page_cache_locked() can be a global symbol
> > > > > with add_to_page_cache_lru() + add_to_page_cache_locked() being just
> > > > > static/inline wrappers around it.
> > > >
> > > > So what happens to BTF if we change this area entirely? Your IDs
> > > > sound like some kind of ABI to me, which is extremely scary.
> > >
> > > Is BTF becoming the new tracepoint? That is, random additions of things like:
> > >
> > > BTF_ID(func,__add_to_page_cache_locked)
> > >
> > > Like was done in commit 1e6c62a882155 ("bpf: Introduce sleepable BPF
> > > programs") without any notification to the maintainers of the
> > > __add_to_page_cache_locked code, will suddenly become an API?
> >
> > huh? what api/abi you're talking about?
>
> If the function __add_to_page_cache_locked were to be removed due to
> the code being rewritten, would it break any user space? If not, then
> there's nothing to worry about. ;-)
That function is marked with ALLOW_ERROR_INJECTION.
So any script that exercises it via debugfs (or via bpf) will not work.
That's nothing new. Same "breakage" happens with kprobes, etc.
The function was marked with error_inject for a reason though.
The refactoring or renaming of this code ideally should provide a way to do
similar pattern of injecting errors in this code path.
It could be a completely new function, of course.
next prev parent reply other threads:[~2020-12-10 3:03 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-06 11:24 [PATCH] mm/filemap: add static for function __add_to_page_cache_locked Alex Shi
2020-11-06 18:24 ` Ira Weiny
2020-11-10 3:09 ` Souptick Joarder
2020-11-10 11:58 ` Alex Shi
2020-11-10 19:50 ` Andrew Morton
2020-11-12 0:18 ` Alex Shi
2020-12-07 8:11 ` Greg Thelen
2020-12-07 8:15 ` Michal Kubecek
2020-12-07 18:35 ` Justin Forbes
2020-12-07 22:44 ` Alexei Starovoitov
2020-12-07 22:53 ` Michal Kubecek
2020-12-07 22:59 ` Alexei Starovoitov
2020-12-08 1:12 ` Alexei Starovoitov
2020-12-09 14:46 ` Stanislaw Gruszka
2020-12-09 15:08 ` Matthew Wilcox
2020-12-09 15:51 ` Stanislaw Gruszka
2020-12-09 18:05 ` Christoph Hellwig
2020-12-09 22:32 ` Steven Rostedt
2020-12-10 1:12 ` Alexei Starovoitov
2020-12-10 2:31 ` Steven Rostedt
2020-12-10 3:02 ` Alexei Starovoitov [this message]
2020-12-09 20:59 ` Tony Luck
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=CAADnVQ+6n4Nf5TczYWqLBrYJF_fEmRVyEbGqmaT0G9XoS7iMxA@mail.gmail.com \
--to=alexei.starovoitov@gmail.com \
--cc=akpm@linux-foundation.org \
--cc=alex.shi@linux.alibaba.com \
--cc=ast@kernel.org \
--cc=bpf@vger.kernel.org \
--cc=daniel@iogearbox.net \
--cc=hch@infradead.org \
--cc=jmforbes@linuxtx.org \
--cc=josef@toxicpanda.com \
--cc=jrdr.linux@gmail.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=mkubecek@suse.cz \
--cc=rostedt@goodmis.org \
--cc=stf_xl@wp.pl \
--cc=willy@infradead.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).