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Date: Fri, 18 Feb 2022 08:51:54 +0100 From: Greg Kroah-Hartman <gregkh@...uxfoundation.org> To: Theodore Ts'o <tytso@....edu> Cc: John Hubbard <jhubbard@...dia.com>, Lee Jones <lee.jones@...aro.org>, linux-ext4@...r.kernel.org, Christoph Hellwig <hch@....de>, Dave Chinner <dchinner@...hat.com>, Goldwyn Rodrigues <rgoldwyn@...e.com>, "Darrick J . Wong" <darrick.wong@...cle.com>, Bob Peterson <rpeterso@...hat.com>, Damien Le Moal <damien.lemoal@....com>, Andreas Gruenbacher <agruenba@...hat.com>, Ritesh Harjani <riteshh@...ux.ibm.com>, Johannes Thumshirn <jth@...nel.org>, linux-xfs@...r.kernel.org, linux-fsdevel@...r.kernel.org, cluster-devel@...hat.com, linux-kernel@...r.kernel.org Subject: Re: [REPORT] kernel BUG at fs/ext4/inode.c:2620 - page_buffers() On Thu, Feb 17, 2022 at 11:08:38PM -0500, Theodore Ts'o wrote: > On Thu, Feb 17, 2022 at 05:06:45PM -0800, John Hubbard wrote: > > Yes. And looking at the pair of backtraces below, this looks very much > > like another aspect of the "get_user_pages problem" [1], originally > > described in Jan Kara's 2018 email [2]. > > Hmm... I just posted my analysis, which tracks with yours; but I had > forgotten about Jan's 2018 e-mail on the matter. > > > I'm getting close to posting an RFC for the direct IO conversion to > > FOLL_PIN, but even after that, various parts of the kernel (reclaim, > > filesystems/block layer) still need to be changed so as to use > > page_maybe_dma_pinned() to help avoid this problem. There's a bit > > more than that, actually. > > The challenge is that fixing this "the right away" is probably not > something we can backport into an LTS kernel, whether it's 5.15 or > 5.10... or 4.19. Don't worry about stable backports to start with. Do it the "right way" first and then we can consider if it needs to be backported or not. thanks, greg k-h
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