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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> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Spamd-Result: default: False [-4.01 / 50.00]; BAYES_HAM(-3.00)[100.00%]; NEURAL_HAM_LONG(-1.00)[-1.000]; MID_RHS_NOT_FQDN(0.50)[]; R_DKIM_ALLOW(-0.20)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; MX_GOOD(-0.01)[]; RCVD_TLS_ALL(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; MISSING_XM_UA(0.00)[]; ARC_NA(0.00)[]; RCPT_COUNT_TWELVE(0.00)[26]; MIME_TRACE(0.00)[0:+]; FREEMAIL_ENVRCPT(0.00)[gmail.com]; DNSWL_BLOCKED(0.00)[2a07:de40:b281:104:10:150:64:97:from]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; FROM_EQ_ENVFROM(0.00)[]; FROM_HAS_DN(0.00)[]; FREEMAIL_CC(0.00)[debian.org,linux-foundation.org,kernel.org,tencent.com,huaweicloud.com,gmail.com,linux.dev,lge.com,infradead.org,google.com,suse.com,linux.alibaba.com,redhat.com,cmpxchg.org,kvack.org,vger.kernel.org,meta.com]; TO_DN_SOME(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; TO_MATCH_ENVRCPT_ALL(0.00)[]; DBL_BLOCKED_OPENRESOLVER(0.00)[imap1.dmz-prg2.suse.org:rdns,imap1.dmz-prg2.suse.org:helo,suse.de:dkim]; SPAMHAUS_XBL(0.00)[2a07:de40:b281:104:10:150:64:97:from]; DKIM_TRACE(0.00)[suse.de:+] X-Spam-Flag: NO X-Spam-Score: -4.01 X-Spam-Level: X-Rspamd-Queue-Id: 070BB81D9E X-Rspamd-Server: rspamd2.dmz-prg2.suse.org X-Rspamd-Action: no action 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