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h=Date:From:To:Cc:Subject:In-Reply-To:References; b=1Ch6BF2pzmORCdDXF6fKXUg5XWDOtX8jdXFDfkMCik+01vWgZJ1w55VmLqepohv8e N2HH1+eTBtBJshqOcMJD8MKD4K+4A1/ewE4P/YoJeysTCe5hs8j82KO00EbkCu9jCZ gfNDcrr3VEJKSxiqXZ5cWBQdlY6kz1nvQFfBsprE= Date: Tue, 18 Aug 2026 12:28:44 -0700 From: Andrew Morton To: Breno Leitao Cc: Chris Li , Kairui Song , Kemeng Shi , Nhat Pham , Baoquan He , Barry Song , Youngjun Park , David Hildenbrand , Miaohe Lin , Oscar Salvador , linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel-team@meta.com, stable@vger.kernel.org Subject: Re: [PATCH] mm, swap: ratelimit bad swap entry reports Message-Id: <20260818122844.71988535d6380ba67e8a2b1a@linux-foundation.org> In-Reply-To: <20260818-swap_part_one-v1-1-a4fc58119fc0@debian.org> References: <20260818-swap_part_one-v1-1-a4fc58119fc0@debian.org> X-Mailer: Sylpheed 3.8.0beta1 (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: rspam04 X-Rspamd-Queue-Id: A7C4CC000C X-Stat-Signature: a3h5zgbnqmczazgkphjgdqumjtuf9iah X-HE-Tag: 1787081326-957884 X-HE-Meta: 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 5YkwuZzY 0SajhaKYAKLf85VPNtD7NcVGZec2ElnDIsxQhiEWGH9rI6pAnFMcnlmP4Y1BvPLL+P32OKSJyxS7gVoFDCyX80NjnVcbvHG+LDMBfv+4AK4LsJkbGSS5ApCTkjIw+bVUc51Ko9YGFD8GUHk45HyQqn7wmtNEQZO5m+5tOquKV1VTlzdyw9gJ+qrYmbR1zWdFNfZc8AFODVYELb/Fv7scv1KaUmD5qwynCJ8gT/t/bx5Q6BbGGyCMSb51F304+wR6fH5IcQ4pA7SlH/oETHLTlRph7zqKRmnlhsBk/NHYK1yCQFcWygshsjiTRBPVYq3zeaCdI++z8FNurZIS7+IZ5thayYOnqz7oQ4sNPqbE9vCk5MloCdjFgIvkfd3mPd+n4oF6e Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, 18 Aug 2026 02:03:40 -0700 Breno Leitao wrote: > A corrupt page table hands the same bogus entry to get_swap_device() on > every access to the mapping, and every rejection is logged. One machine > logged 6185620 copies of the same line in a few hours. > > swap_dup_entry_direct() prints the same message from the fork path, once > per call: the WARN_ON_ONCE() guarding it warns once, the pr_err() inside > does not. > > Rate limit all three prints. Sashiko suggests that ratelimiting these might cause pre-existing problems to become worse: https://sashiko.dev/#/patchset/20260818-swap_part_one-v1-1-a4fc58119fc0@debian.org The problem it's identifying does require that unrelated things go wrong first - get_swap_device() failed, swap_retry_table_alloc() did a retry. So presumably you wouldn't have hit this in testing. Sigh, so much to fix.