From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 04B44C5DF70 for ; Mon, 17 Aug 2026 09:31:32 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id B620D6B00A7; Mon, 17 Aug 2026 05:31:30 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id B13536B00AC; Mon, 17 Aug 2026 05:31:30 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id A01446B00AD; Mon, 17 Aug 2026 05:31:30 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id 6D7C56B00A7 for ; Mon, 17 Aug 2026 05:31:30 -0400 (EDT) Received: from smtpin17.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay06.hostedemail.com (Postfix) with ESMTP id CF0C8A31BF for ; Mon, 17 Aug 2026 09:31:29 +0000 (UTC) X-FDA: 85110243498.17.AA95C3A Received: from stravinsky.debian.org (stravinsky.debian.org [82.195.75.108]) by imf14.hostedemail.com (Postfix) with ESMTP id 23770100002 for ; Mon, 17 Aug 2026 09:31:28 +0000 (UTC) Authentication-Results: imf14.hostedemail.com; dkim=pass header.d=debian.org header.s=smtpauto.stravinsky header.b=r9Gk2fZB; spf=pass (imf14.hostedemail.com: domain of leitao@debian.org designates 82.195.75.108 as permitted sender) smtp.mailfrom=leitao@debian.org; dmarc=pass (policy=none) header.from=debian.org ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1786959088; b=tVmNQvbpde6VK4yLpIJDRvblG/7Lf3+ScIZ2vMpYDWe7C3F9UUFETjKIwKZTSl7luqslaL UaV7X7iCWtPA8h0CbzJWX6usgaiEJ6MkL4XZLgPXPoHrTkre4EJyhsxRQ9gMrmUjjTOXk3 nOsd9BFcJtR+/+nn21Stej2dyUcLoYs= ARC-Authentication-Results: i=1; imf14.hostedemail.com; dkim=pass header.d=debian.org header.s=smtpauto.stravinsky header.b=r9Gk2fZB; spf=pass (imf14.hostedemail.com: domain of leitao@debian.org designates 82.195.75.108 as permitted sender) smtp.mailfrom=leitao@debian.org; dmarc=pass (policy=none) header.from=debian.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1786959088; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=BY2LkZEV75VdRKC+EAUB3TNiV4cpx9y+rtp1/41c53k=; b=kXnYThLfJLLZceGMwINuXf0ardCTXXd25lUY97w8XdlShJd0o94vFz7SO6Bl5kZB5hDLtR OHomi47kp2gqRCi/K3Umg4c3EowXP1sGHehjuWXMzvnqsvz3BnqgC//49/9wcC8C0iflVa YrRncdTY9VLvJqgs+qrHICX/s17Hr4s= DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=debian.org; s=smtpauto.stravinsky; h=X-Debian-User:In-Reply-To:Content-Transfer-Encoding: Content-Type:MIME-Version:References:Message-ID:Subject:Cc:To:From:Date: Reply-To:Content-ID:Content-Description; bh=BY2LkZEV75VdRKC+EAUB3TNiV4cpx9y+rtp1/41c53k=; b=r9Gk2fZB9cfEG0VaSO5oI/fqP5 g69PCBq5qcPnhfxiCYHfmNpdid+3WbPGyvqzvqCYtWzGtl5qLBa6gHRk0TGW707n6qhVdO3ZeM/Nr f6j7PKlzlS4WhMqfgeUEDKmmmNsxsRTIC9z/GCIY3peYbeTWdyi8xJWjxUxTVcRTb9eaaZjYHP71n G6Sc5apuxY3TU4sQsccFEHic/NQRS1XoHEwco1HpYK3OSrMvD2eemcJ6CYBlQtWM9sTGo/92tmyQL EiQaVyQqJUgZ04WpFVGEwE8xO21n9U+kp10Q7V7LYgN8kC/jYv+ramdKGwYaI8MJ1DwC+uSpFspAc LIJteWuQ==; Received: from authenticated-user by stravinsky.debian.org with esmtpsa (TLS1.3:ECDHE_X25519__RSA_PSS_RSAE_SHA256__AES_256_GCM:256) (Exim 4.96) (envelope-from ) id 1wvtfu-0087yL-0m; Mon, 17 Aug 2026 09:30:34 +0000 Date: Mon, 17 Aug 2026 02:30:27 -0700 From: Breno Leitao To: Barry Song Cc: Andrew Morton , Chris Li , Kairui Song , Kemeng Shi , Nhat Pham , Baoquan He , Youngjun Park , David Hildenbrand , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Jann Horn , Pedro Falcato , 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 v2 3/3] mm: fail the fault on a malformed swap entry instead of retrying it Message-ID: References: <20260813-swap-v2-0-4a625ccabdae@debian.org> <20260813-swap-v2-3-4a625ccabdae@debian.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Debian-User: leitao X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 23770100002 X-Stat-Signature: 7y3betdmrtcc1jijgji3ymq9gfmu5qnu X-HE-Tag: 1786959088-202346 X-HE-Meta: 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 +u7yVdVw f88/7jTFwzA/70iijJNjWF00t0ypoKqFeV7WmHnwBx5yMYBp8Wt0SFouFcEdJ75tbWHkR2HoTbnAkN3VB8dCC185PolIvORkyu6wQNqEQS4cVX0vFQNnz4Xze+T8l7kLPLjAWTWFgFw520cq6nfQPH8NAImTqDChJ8yT+oZyMqWM72sR50uo+CPV4zfapvy3YV14bIpptZNB/QdSqFA2LwXdfJtr5OUyB37E3RSaqu36R7UYB0+R9ke1vfhIsUBBP4mcM9vEXJQPIIVR1FcTruyMiTC6lWpv3L87vIpJWzvUE7Hg= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, Aug 17, 2026 at 06:22:41AM +0800, Barry Song wrote: > On Thu, Aug 13, 2026 at 6:02 PM Breno Leitao wrote: > > > > do_swap_page() returns 0 when get_swap_device() fails, which the fault > > handler reads as "handled". For an entry that can never become valid > > the retry takes the same fault again, so the thread spins forever, > > retrying on the same fault. > > > > Return VM_FAULT_SIGBUS (Bad access) for a malformed entry (pr_err() was > > called at get_swap_device()). > > > > Signed-off-by: Breno Leitao > > --- > > mm/memory.c | 3 +++ > > 1 file changed, 3 insertions(+) > > > > diff --git a/mm/memory.c b/mm/memory.c > > index 7201e848129a7..fa2b3d2ad3202 100644 > > --- a/mm/memory.c > > +++ b/mm/memory.c > > @@ -4957,6 +4957,9 @@ vm_fault_t do_swap_page(struct vm_fault *vmf) > > /* Prevent swapoff from happening to us, and reject a bad entry. */ > > si = get_swap_device(entry); > > if (IS_ERR_OR_NULL(si)) { > > + /* A malformed entry never becomes valid, so don't retry it. */ > > + if (IS_ERR(si)) > > + ret = VM_FAULT_SIGBUS; > > > Hi Breno, > > Since you now return VM_FAULT_SIGBUS, the page fault should no > longer retry repeatedly. Do we still need patch 1/3, which adds the > rate-limited printk? Yes, I still think we need it, for a few reasons: 1) A different bug could just as easily trigger the same message flood again. 2) I don't see a case where flooding the log with this message would help. If it keeps firing, something else is already broken, and the repeated message itself adds nothing useful. 3) From a monitoring perspective, I'd guess 95% of our log messages should be rate limited anyway, and this one would fall into this category. You think this one shouldn't be ratelimited? Thanks for the review, --breno