linux-kernel - Re: [PATCH] lib/buildid: use __kernel

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Message-ID: <aUONb6wqk7Q-QxC9@infradead.org>
Date: Wed, 17 Dec 2025 21:13:19 -0800
From: Christoph Hellwig <hch@...radead.org>
To: Shakeel Butt <shakeel.butt@...ux.dev>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
	Matthew Wilcox <willy@...radead.org>,
	Andrii Nakryiko <andrii@...nel.org>,
	Shaurya Rane <ssrane_b23@...vjti.ac.in>,
	"Darrick J . Wong" <djwong@...nel.org>,
	Christoph Hellwig <hch@...radead.org>,
	Alexei Starovoitov <ast@...nel.org>,
	Daniel Borkmann <daniel@...earbox.net>,
	Meta kernel team <kernel-team@...a.com>, bpf@...r.kernel.org,
	linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	syzbot+09b7d050e4806540153d@...kaller.appspotmail.com
Subject: Re: [PATCH] lib/buildid: use __kernel_read() for sleepable context

On Wed, Dec 17, 2025 at 04:58:18PM -0800, Shakeel Butt wrote:
> For the sleepable context, convert freader to use __kernel_read()
> instead of direct page cache access via read_cache_folio(). This
> simplifies the faultable code path by using the standard kernel file
> reading interface which handles all the complexity of reading file data.
> 
> At the moment we are not changing the code for non-sleepable context
> which uses filemap_get_folio() and only succeeds if the target folios
> are already in memory and up-to-date. The reason is to keep the patch
> simple and easier to backport to stable kernels.
> 
> Syzbot repro does not crash the kernel anymore and the selftests run
> successfully.
> 
> In the follow up we will make __kernel_read() with IOCB_NOWAIT work for
> non-sleepable contexts. In addition, I would like to replace the
> secretmem check with a more generic approach and will add fstest for the
> buildid code.

Getting the code further away from messing with internals is good:

Reviewed-by: Christoph Hellwig <hch@....de>

I do not think making IOCB_NOWAIT never wait is feasily, though for the
next step.