From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from stravinsky.debian.org (stravinsky.debian.org [82.195.75.108]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 8784A311C2C; Fri, 15 May 2026 13:14:47 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=82.195.75.108 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778850889; cv=none; b=tDprRJpNYyDqu5I26A6i4uJf7cA1WhkMIO+5tdBNAr5qS2uEZjYeC0E43ot6rAYqBg23ca0gTJ/RVYoWXfPMV601mNknUdVK10CsUQ1SzxN0Zu6XI07kFJ47xPMo/Np9HZUQb12W/3Knnopf5x7SGcrOZH6qoDYbBqk8tZ+/N/E= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778850889; c=relaxed/simple; bh=4DW1KFLKdY0r9Kt85uXfYMWGPLMqHEQnYtena6SVqwc=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=u8Yw8vnoxwxdv/CtuBaj5xZZ4pXwqknObLVC0Lmfscuvby4b6oqV2wTjV0Rwsbo7sKXQnKcgg48Ez+s3RC536hOkwe4Wktrg/aZQxi0qvRnWVQvDQfGPjH3FtPKINboAVTUUagBCQX6YPzQoOVSGOifULOZUwGnGo9zNtZ6SXVM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=debian.org; spf=pass smtp.mailfrom=debian.org; dkim=pass (2048-bit key) header.d=debian.org header.i=@debian.org header.b=YO6HHuhT; arc=none smtp.client-ip=82.195.75.108 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=debian.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=debian.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=debian.org header.i=@debian.org header.b="YO6HHuhT" 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=Pmx2rneBBjmIsZbvqyQI5Qj38w0M3wSqScjqM675SPE=; b=YO6HHuhTFg9PhNc1fOrsmCg0l2 coFCfL/HXWdkEJQ/NNKVRj19rXWjjJl5HBw6M88KuaCjeYzYEPxkD/PkxEoOUOEpDSXao2gSZ5fNV y2r2DTZTvmnVMIM7EDLOTJKm80si4Z51/LIYtXbCGrLWy68gBkSfDd3begZfr1Tl9UpTgOTCJY8k3 larcZFhBbwn6Ob9lxog2bbdoGpydWJoRKteQBRuuG59KTjRkgsoB1omyQ2EO0LFmGAFwi8y4O91SP UuCvmx/NcPNmSfXVwpJq08KpkIpKycDMtaozxfkO3MZka5q8HtenV+xPq1+8eNV+rO49xWD9L4NcB YfFZfRSg==; 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 1wNsMf-004kzr-03; Fri, 15 May 2026 13:14:05 +0000 Date: Fri, 15 May 2026 06:13:58 -0700 From: Breno Leitao To: Lance Yang Cc: linmiaohe@huawei.com, akpm@linux-foundation.org, david@kernel.org, ljs@kernel.org, vbabka@kernel.org, rppt@kernel.org, surenb@google.com, mhocko@suse.com, shuah@kernel.org, nao.horiguchi@gmail.com, rostedt@goodmis.org, mhiramat@kernel.org, mathieu.desnoyers@efficios.com, corbet@lwn.net, skhan@linuxfoundation.org, liam@infradead.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-trace-kernel@vger.kernel.org, kernel-team@meta.com Subject: Re: [PATCH v7 2/6] mm/memory-failure: surface unhandlable kernel pages as -ENOTRECOVERABLE Message-ID: References: <20260515070353.87244-1-lance.yang@linux.dev> Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20260515070353.87244-1-lance.yang@linux.dev> X-Debian-User: leitao On Fri, May 15, 2026 at 03:03:53PM +0800, Lance Yang wrote: > > On Thu, May 14, 2026 at 07:37:14AM -0700, Breno Leitao wrote: > >On Thu, May 14, 2026 at 09:28:30PM +0800, Lance Yang wrote: > >> > >> On Wed, May 13, 2026 at 08:39:33AM -0700, Breno Leitao wrote: > >> >get_any_page() collapses three different failure modes into a single > >> >-EIO return: > >> > > >> > * the put_page race in the !count_increased path; > >> > * the HWPoisonHandlable() rejection that bounces out of > >> > __get_hwpoison_page() with -EBUSY and exhausts shake_page() retries; > >> > * the HWPoisonHandlable() rejection that goes through the > >> > count_increased / put_page / shake_page retry loop. > >> > > >> >The first is transient (the page is racing with the allocator). The > >> >second can be either transient (a userspace folio briefly off LRU > >> >during migration/compaction) or stable (slab/vmalloc/page-table/ > >> >kernel-stack pages). The third describes a stable kernel-owned page > >> >that the count_increased=true caller already held a reference on. > >> > > >> >Distinguish them on the return path: keep -EIO for both the put_page > >> >race and the -EBUSY-after-retries branch (shake_page() cannot drag a > >> >folio back from active migration, so we cannot prove the page is > >> >permanently kernel-owned from there), keep -EBUSY for the allocation > >> >race (unchanged), and return -ENOTRECOVERABLE only from the > >> >count_increased-true HWPoisonHandlable() rejection that exhausts its > >> >retries -- the caller's reference is structural evidence that the > >> >page is owned by the kernel. > >> > > >> >Extend the unhandlable-page pr_err() to fire for either errno and > >> >update the get_hwpoison_page() kerneldoc. > >> > > >> >memory_failure() still folds every negative return into > >> >MF_MSG_GET_HWPOISON via its existing "else if (res < 0)" branch, so > >> >this patch is a no-op for users of memory_failure() and only changes > >> >the errno that soft_offline_page() can propagate to its callers. A > >> >follow-up wires the new return code through memory_failure() and > >> >reports MF_MSG_KERNEL for the unrecoverable cases. > >> > > >> >Suggested-by: David Hildenbrand > >> >Signed-off-by: Breno Leitao > >> >--- > >> > mm/memory-failure.c | 18 +++++++++++++++--- > >> > 1 file changed, 15 insertions(+), 3 deletions(-) > >> > > >> >diff --git a/mm/memory-failure.c b/mm/memory-failure.c > >> >index 49bcfbd04d213..bae883df3ccb2 100644 > >> >--- a/mm/memory-failure.c > >> >+++ b/mm/memory-failure.c > >> >@@ -1408,6 +1408,15 @@ static int get_any_page(struct page *p, unsigned long flags) > >> > shake_page(p); > >> > goto try_again; > >> > } > >> >+ /* > >> >+ * Return -EIO rather than -ENOTRECOVERABLE: this > >> >+ * branch is also reached for pages that are merely > >> >+ * off-LRU transiently (e.g. a folio in the middle > >> >+ * of migration or compaction), which shake_page() > >> >+ * cannot drag back. The caller cannot prove the > >> >+ * page is permanently kernel-owned from here, so > >> >+ * keep it on the recoverable errno. > >> >+ */ > >> > ret = -EIO; > >> > goto out; > >> > } > >> >@@ -1427,10 +1436,10 @@ static int get_any_page(struct page *p, unsigned long flags) > >> > goto try_again; > >> > } > >> > put_page(p); > >> >- ret = -EIO; > >> >+ ret = -ENOTRECOVERABLE; > >> > } > >> > out: > >> >- if (ret == -EIO) > >> >+ if (ret == -EIO || ret == -ENOTRECOVERABLE) > >> > pr_err("%#lx: unhandlable page.\n", page_to_pfn(p)); > >> > > >> > return ret; > >> >@@ -1487,7 +1496,10 @@ static int __get_unpoison_page(struct page *page) > >> > * -EIO for pages on which we can not handle memory errors, > >> > * -EBUSY when get_hwpoison_page() has raced with page lifecycle > >> > * operations like allocation and free, > >> >- * -EHWPOISON when the page is hwpoisoned and taken off from buddy. > >> >+ * -EHWPOISON when the page is hwpoisoned and taken off from buddy, > >> >+ * -ENOTRECOVERABLE for stable kernel-owned pages the handler > >> >+ * cannot recover (PG_reserved, slab, vmalloc, page tables, > >> >+ * kernel stacks, and similar non-LRU/non-buddy pages). > >> > >> Did you test this patch series? I don't see how we ever get to > >> -ENOTRECOVERABLE there ... > > > >Yes, I did. I am using the following test case: > > Okay. > > >https://github.com/leitao/linux/commit/cfebe84ddeab5ac34ed456331db980d57e7025dc > > > > # RUN_DESTRUCTIVE=1 tools/testing/selftests/mm/hwpoison-panic.sh > > # enabling /proc/sys/vm/panic_on_unrecoverable_memory_failure > > # injecting hwpoison at phys 0x2a00000 (Kernel rodata) > > # expecting kernel panic: 'Memory failure: : unrecoverable page' > > [ 501.113256] Memory failure: 0x2a00: recovery action for reserved kernel page: Ignored > > [ 501.113956] Kernel panic - not syncing: Memory failure: 0x2a00: unrecoverable page > > > > > >> Even with MF_COUNT_INCREASED, the first pass does: > >> > >> if (flags & MF_COUNT_INCREASED) > >> count_increased = true; > >> > >> [...] > >> > >> if (PageHuge(p) || HWPoisonHandlable(p, flags)) { > >> ret = 1; > >> } else { > >> if (pass++ < GET_PAGE_MAX_RETRY_NUM) { <- > >> put_page(p); > >> shake_page(p); > >> count_increased = false; > >> goto try_again; <- > >> } > >> put_page(p); > >> ret = -ENOTRECOVERABLE; > >> } > >> > >> Then we come back with count_increased=false: > >> > >> try_again: > >> if (!count_increased) { > >> ret = __get_hwpoison_page(p, flags); <- > >> if (!ret) { > >> [...] > >> } else if (ret == -EBUSY) { <- > >> [...] > >> ret = -EIO; > >> goto out; <- > >> } > >> } > >> > >> For slab/vmalloc/page-table pages, __get_hwpoison_page() returns -EBUSY: > >> > >> if (!HWPoisonHandlable(&folio->page, flags)) > >> return -EBUSY; > >> > >> so they still seem to end up as -EIO ... Am I missing something? > > > >You are not, and thanks for catching this. I traced it again and the > >-ENOTRECOVERABLE branch is unreachable for slab/vmalloc/page-table pages > >exactly as you described. The __get_hwpoison_page() → -EBUSY → shake → retry > >loop catches them first and they exit as -EIO. > > Wonder if it would be simpler to just do a positive check near the top > of get_any_page() instead. Something like: > > static bool hwpoison_unrecoverable_kernel_page(struct page *page, > unsigned long flags) Ack. We probably want to call it something like HWPoisonKernelOwned() to follow the same naming sematics of these helpers, such as HWPoisonHandlable() By the way, I will re-include the self test back to this patch series, In case they are not useful, we do not merge it. Thanks for the review, --breno