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Tue, 11 Aug 2026 16:48:54 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id bql5E3ZSe2pxLQAAD6G6ig (envelope-from ); Tue, 11 Aug 2026 16:48:54 +0000 Date: Tue, 11 Aug 2026 17:48:52 +0100 From: Pedro Falcato To: "David Hildenbrand (Arm)" Cc: Breno Leitao , Andrew Morton , Chris Li , Kairui Song , Kemeng Shi , Nhat Pham , Baoquan He , Barry Song , Youngjun Park , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Jann Horn , Hugh Dickins , Baolin Wang , Peter Xu , Johannes Weiner , Yosry Ahmed , Chengming Zhou , linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel-team@meta.com Subject: Re: [PATCH 1/3] mm, swap: ratelimit bad swap entry reports in get_swap_device() Message-ID: References: <20260810-swap-v1-0-375ef0767206@debian.org> <20260810-swap-v1-1-375ef0767206@debian.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Action: no action X-Rspamd-Queue-Id: BA992A0013 X-Rspam-User: X-Stat-Signature: 68ifdtx64cs8yb4ez7gyxo789w733sej X-Rspamd-Server: rspam06 X-HE-Tag: 1786466945-676300 X-HE-Meta: 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 C8DP1yLM g7NnVhdAPSRU+N5Jm8E69XcCd3IZlBBmj29GohEnztMn3CgRsP9apOKwGtB9XYJYLOI/ZVobBDeCwG2HtrJaGlilFG9ZLtp/GOuLfH/folhY8Zg9Xfu70kcxSMfLRA4R3OZK5UDgg+0Rxx66+Z564wUeCDn8FSIOJbP6LSsgvo5qmqkUe3DlaiKejdA2VOan3V7C//zuXhYQb8V3XDt1Ju9waWGluaiLgKx6FsYZrhQeNvQ1+B2O87oqT/mpqXX73wHa2ZCHnAl3VA/689QmbcVOERBaDwIEI2R9ek5J6XFWUHJD/C1sg/P/5DFv/OfBkJBQzophGohtayFa65tbmHsOdN5st5Ovf/3XhjQBrq+uJk3rgjCi+Lil8m/90tJgQnMkQOYEk9ZgFBUh2c0xS1g3suA== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, Aug 11, 2026 at 05:33:54PM +0200, David Hildenbrand (Arm) wrote: > On 8/10/26 18:26, 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. > > > > Rate limit both prints. > > > > Signed-off-by: Breno Leitao > > --- > > mm/swapfile.c | 4 ++-- > > 1 file changed, 2 insertions(+), 2 deletions(-) > > > > diff --git a/mm/swapfile.c b/mm/swapfile.c > > index 4d4e3e3059f6b..9ab11dc24e4f1 100644 > > --- a/mm/swapfile.c > > +++ b/mm/swapfile.c > > @@ -1899,11 +1899,11 @@ struct swap_info_struct *get_swap_device(swp_entry_t entry) > > > > return si; > > bad_nofile: > > - pr_err("%s: %s%08lx\n", __func__, Bad_file, entry.val); > > + pr_err_ratelimited("%s: %s%08lx\n", __func__, Bad_file, entry.val); > > out: > > return NULL; > > put_out: > > - pr_err("%s: %s%08lx\n", __func__, Bad_offset, entry.val); > > + pr_err_ratelimited("%s: %s%08lx\n", __func__, Bad_offset, entry.val); > > percpu_ref_put(&si->users); > > return NULL; > > } > > > > In print_bad_page_map() we use something more advanced > (is_bad_page_map_ratelimited): essentially a burst of 60 followed by 1minute of > silence. Is it more advanced? It just looks like a handcoded version of __ratelimit. ... I hate it now. I'll send a patch I guess. > Couldn't some of the stuff you drop here (different entries) be similarly valuable? I think we generally do a terribly lousy job reporting these kinds of failures. Would be awesome to log this elsewhere, or possibly send something like a SIGBUS to the faulting process, for instance. (and this kind of stuff should very much be handleable by userspace, otherwise programs can drop data without even finding out about it) -- Pedro