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bh=HByyQifs96c18FNN/v288o+8EnsWfHwi6zdKQPZ0gd8=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=cZ6Jq8E6rRBrz16vl3O1vh+ktQtbQJchzfkGEkCOIS4TMOJH3tJ93KA8feGoPJ41l 0IdDHnI1Oru8/8uWqrzYLZ+GpJ9BMZ5/QcORfOoYwmPhoVcT6yCYGjWBLG9LT5dKpa X040AEif+tnRisK/OlZiPisgI3iX8F6wUVFXPvVs= Date: Mon, 24 Apr 2023 15:07:26 -0700 From: Andrew Morton To: Hugh Dickins Cc: Ivan Orlov , Jiaqi Yan , David Stevens , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH next] mm/khugepaged: fix conflicting mods to collapse_file() Message-Id: <20230424150726.a53d3ebe47ad84e55e16d4a6@linux-foundation.org> In-Reply-To: References: X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam03 X-Stat-Signature: 71s3k66z15rti39f9wfi43zpk1i7fyd5 X-Rspamd-Queue-Id: C480814000E X-HE-Tag: 1682374048-500612 X-HE-Meta: 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 S6jz0Nkq N/D12LI2kOatgtXqNMocABWibS2goMwVgjRFFL4Til5ZWj7myb1Sy6SeaEYxWbjA1H26rpIc2IdKHTO4pQTTZOq+Ak8tqgKDPzyZltHlRVeEoilvxjdVBPi+QgGLmzQz7jQaT7MnL8tLFZNtuQBm1MVyuPbgY1mheCcDHbk4OO4WndNweJg5a8BL1bxIkuqnsD92qTjcfYSgU4TFg/rgHRqWYPgtlt5cNGyUnEgz6wV7ZCvzx6qPDfixxacBWWd0/XO9PhxKCBPpISHlk6UTuAfeMG8aR2N9bSyxVWkISzDhBb3XYXa/yJ5rNBw4FVuoQH6vmwJVSsmU0XCx4Wl1/PKUcSOiCKUxtWAYKZsElyxoX/BpsuRmdRFYWoIkFsfLuh5LtipU6hrvpopcvs+Tt49NJp7lFQh/l8hJqlBqZXsCX/m+obTHlNa+JpPYendeAsmXo0QKsxbBCjU93Y9GNA/ZCaA== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Sat, 22 Apr 2023 21:47:20 -0700 (PDT) Hugh Dickins wrote: > Inserting Ivan Orlov's syzbot fix commit 2ce0bdfebc74 > ("mm: khugepaged: fix kernel BUG in hpage_collapse_scan_file()") > ahead of Jiaqi Yan's and David Stevens's commits > 12904d953364 ("mm/khugepaged: recover from poisoned file-backed memory") > cae106dd67b9 ("mm/khugepaged: refactor collapse_file control flow") > ac492b9c70ca ("mm/khugepaged: skip shmem with userfaultfd") > (all of which restructure collapse_file()) did not work out well. > > xfstests generic/086 on huge tmpfs (with accelerated khugepaged) freezes > (if not on the first attempt, then the 2nd or 3rd) in find_lock_entries() > while doing drop_caches: the file's xarray seems to have been corrupted, > with find_get_entry() returning nonsense which makes no progress. > > Bisection led to ac492b9c70ca; and diff against earlier working linux-next > suggested that it's probably down to an errant xas_store(), which does not > belong with the later changes (and nor does the positioning of warnings). > The later changes look as if they fix the syzbot issue independently. > > Remove most of what's left of 2ce0bdfebc74: just leave one WARN_ON_ONCE > (xas_error) after the final xas_store() of the multi-index entry. > Sigh. Thanks. I thought I'd successfully sorted that mess out.