linux-ext4 - Re: kernel BUG at fs/ext4/inode.c:1914

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Message-ID: <ea6a88c7-5603-af1d-e775-0857fc605224@icdsoft.com>
Date:   Wed, 15 Mar 2023 13:27:11 +0200
From:   Ivan Zahariev <famzah@...soft.com>
To:     Jan Kara <jack@...e.cz>, Theodore Ts'o <tytso@....edu>
Cc:     linux-ext4@...r.kernel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: kernel BUG at fs/ext4/inode.c:1914 - page_buffers()

On 12.1.2023 г. 17:07, Jan Kara wrote:
> So after a bit of thought I agree that the commit 5c48a7df91499 ("ext4: fix
> an use-after-free issue about data=journal writeback mode") is broken. The
> problem is when we unlock the page in __ext4_journalled_writepage() anybody
> else can come, writeout the page, and reclaim page buffers (due to memory
> pressure). Previously, bh references were preventing the buffer reclaim to
> happen but now there's nothing to prevent it.
>
> My rewrite of data=journal writeback path fixes this problem as a
> side-effect but perhaps we need a quickfix for stable kernels? Something
> like attached patch?
>
> 								Honza

Do you consider this patch production ready?

Should we test it on real production machines with a peace of mind that 
nothing can go wrong in regards to data loss or corruption?

--Ivan