From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-178.mta1.migadu.com (out-178.mta1.migadu.com [95.215.58.178]) (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 26E8B13AF2 for ; Thu, 22 Aug 2024 09:46:07 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.178 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1724319971; cv=none; b=QdR5LZYkusPqPx5uA7w7HP5eSjYHfreM+6KWmeXfTo8sWK8IkwDpZfoTF0g0VOYiJFW5lmlZAMN6VjVZIkyA/x4S56LED9H395OFNhR8k97zg8Tx3gtiaF4SGD0mYHRdxCnyZs0zqV3JeCrYlHVfXNeqjO52DuIqqa3Sw24RnDs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1724319971; c=relaxed/simple; bh=nMM5xc87HjLe57Hpiot1MTxh121OV1wiV02Mms8rhng=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=HRR4eP/TpOWFT8p0o5JBuMw6KgN9jEk/0GsmwVNvfrXKKsU7E27l6TtQ/j1Xp8S2LK99vZ38ktrMYC9rIXNZDyPtpktZusLxKjm61vGMmOP1dRu5bDnVKl2e2ShjMTDmBDeRhvnZCz3iKorKH9g9sifhVS53JfMAQp/QDsvWvvw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=ZnmCjvha; arc=none smtp.client-ip=95.215.58.178 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="ZnmCjvha" Message-ID: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1724319965; h=from:from: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; bh=RpLoHGwQLK8WQXV+c9zw5UdCABNMrKwbUQvPoiXDGGI=; b=ZnmCjvhaKsFk3ZN13JjRJLCgg0qX5lN0bs07e3X85nnPxEeM++zMfsEIHJu8iXteKEe1jG gFmQ+dPpCtMyuWuUA4D7h7Qhu5W+/GFhU2FNenvWhEPx/YkhUtP/FmZuAqX7MKCj0tlrN2 XoUn5two9gmQVZ/ns2jn5Ee+X7OsyNE= Date: Thu, 22 Aug 2024 17:45:40 +0800 Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Subject: Re: [PATCH] codetag: debug: mark codetags for pages which transitioned from being poison to unpoison as empty To: Miaohe Lin , surenb@google.com, kent.overstreet@linux.dev Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Hao Ge , stable@vger.kernel.org, nao.horiguchi@gmail.com, akpm@linux-foundation.org, pasha.tatashin@soleen.com, david@redhat.com References: <20240822025800.13380-1-hao.ge@linux.dev> X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Hao Ge In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT Hi Miaohe Thank you for taking the time to review this patch. On 8/22/24 16:04, Miaohe Lin wrote: > On 2024/8/22 10:58, Hao Ge wrote: >> From: Hao Ge >> > Thanks for your patch. > >> The PG_hwpoison page will be caught and isolated on the entrance to >> the free buddy page pool. so,when we clear this flag and return it >> to the buddy system,mark codetags for pages as empty. >> > Is below scene cause the problem? > > 1. Pages are allocated. pgalloc_tag_add() will be called when prep_new_page(). > > 2. Pages are hwpoisoned. memory_failure() will set PG_hwpoison flag and pgalloc_tag_sub() > will be called when pages are caught and isolated on the entrance to buddy. > > 3. unpoison_memory cleared flags and sent the pages to buddy. pgalloc_tag_sub() will be > called again in free_pages_prepare(). > > So there is a imbalance that pgalloc_tag_add() is called once and pgalloc_tag_sub() is called twice? As you said, that's exactly the case. > > If so, let's think about more complicated scene: > > 1. Same as above. > > 2. Pages are hwpoisoned. But memory_failure() fails to handle it. So PG_hwpoison flag is set > but pgalloc_tag_sub() is not called (pages are not sent to buddy). > > 3. unpoison_memory cleared flags and calls clear_page_tag_ref() without calling pgalloc_tag_sub() > first. Will this cause problem? > > Though this should be really rare... > > Thanks. > . Great, I didn't anticipate this scenario. When we call clear_page_tag_ref() without calling pgalloc_tag_sub(), It will cause exceptions in|tag->counters->bytes|and|tag->counters->calls|. We can add a layer of protection to handle it The pseudocode is as follows: if (mem_alloc_profiling_enabled()) {         union codetag_ref *ref = get_page_tag_ref(page);         if (ref) {             if( ref->ct != NULL && !is_codetag_empty(ref))             {                 tag = ct_to_alloc_tag(ref->ct);                 this_cpu_sub(tag->counters->bytes, bytes);                 this_cpu_dec(tag->counters->calls);             }             set_codetag_empty(ref);             put_page_tag_ref(ref);         } } Hi Suren and Kent Do you have any suggestions for this? If it's okay, I'll add comments and include this pseudocode in|clear_page_tag_ref|. >> It was detected by [1] and the following WARN occurred: >> >> [ 113.930443][ T3282] ------------[ cut here ]------------ >> [ 113.931105][ T3282] alloc_tag was not set >> [ 113.931576][ T3282] WARNING: CPU: 2 PID: 3282 at ./include/linux/alloc_tag.h:130 pgalloc_tag_sub.part.66+0x154/0x164 >> [ 113.932866][ T3282] Modules linked in: hwpoison_inject fuse ip6t_rpfilter ip6t_REJECT nf_reject_ipv6 ipt_REJECT nf_reject_ipv4 xt_conntrack ebtable_nat ebtable_broute ip6table_nat ip6table_man4 >> [ 113.941638][ T3282] CPU: 2 UID: 0 PID: 3282 Comm: madvise11 Kdump: loaded Tainted: G W 6.11.0-rc4-dirty #18 >> [ 113.943003][ T3282] Tainted: [W]=WARN >> [ 113.943453][ T3282] Hardware name: QEMU KVM Virtual Machine, BIOS unknown 2/2/2022 >> [ 113.944378][ T3282] pstate: 40400005 (nZcv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--) >> [ 113.945319][ T3282] pc : pgalloc_tag_sub.part.66+0x154/0x164 >> [ 113.946016][ T3282] lr : pgalloc_tag_sub.part.66+0x154/0x164 >> [ 113.946706][ T3282] sp : ffff800087093a10 >> [ 113.947197][ T3282] x29: ffff800087093a10 x28: ffff0000d7a9d400 x27: ffff80008249f0a0 >> [ 113.948165][ T3282] x26: 0000000000000000 x25: ffff80008249f2b0 x24: 0000000000000000 >> [ 113.949134][ T3282] x23: 0000000000000001 x22: 0000000000000001 x21: 0000000000000000 >> [ 113.950597][ T3282] x20: ffff0000c08fcad8 x19: ffff80008251e000 x18: ffffffffffffffff >> [ 113.952207][ T3282] x17: 0000000000000000 x16: 0000000000000000 x15: ffff800081746210 >> [ 113.953161][ T3282] x14: 0000000000000000 x13: 205d323832335420 x12: 5b5d353031313339 >> [ 113.954120][ T3282] x11: ffff800087093500 x10: 000000000000005d x9 : 00000000ffffffd0 >> [ 113.955078][ T3282] x8 : 7f7f7f7f7f7f7f7f x7 : ffff80008236ba90 x6 : c0000000ffff7fff >> [ 113.956036][ T3282] x5 : ffff000b34bf4dc8 x4 : ffff8000820aba90 x3 : 0000000000000001 >> [ 113.956994][ T3282] x2 : ffff800ab320f000 x1 : 841d1e35ac932e00 x0 : 0000000000000000 >> [ 113.957962][ T3282] Call trace: >> [ 113.958350][ T3282] pgalloc_tag_sub.part.66+0x154/0x164 >> [ 113.959000][ T3282] pgalloc_tag_sub+0x14/0x1c >> [ 113.959539][ T3282] free_unref_page+0xf4/0x4b8 >> [ 113.960096][ T3282] __folio_put+0xd4/0x120 >> [ 113.960614][ T3282] folio_put+0x24/0x50 >> [ 113.961103][ T3282] unpoison_memory+0x4f0/0x5b0 >> [ 113.961678][ T3282] hwpoison_unpoison+0x30/0x48 [hwpoison_inject] >> [ 113.962436][ T3282] simple_attr_write_xsigned.isra.34+0xec/0x1cc >> [ 113.963183][ T3282] simple_attr_write+0x38/0x48 >> [ 113.963750][ T3282] debugfs_attr_write+0x54/0x80 >> [ 113.964330][ T3282] full_proxy_write+0x68/0x98 >> [ 113.964880][ T3282] vfs_write+0xdc/0x4d0 >> [ 113.965372][ T3282] ksys_write+0x78/0x100 >> [ 113.965875][ T3282] __arm64_sys_write+0x24/0x30 >> [ 113.966440][ T3282] invoke_syscall+0x7c/0x104 >> [ 113.966984][ T3282] el0_svc_common.constprop.1+0x88/0x104 >> [ 113.967652][ T3282] do_el0_svc+0x2c/0x38 >> [ 113.968893][ T3282] el0_svc+0x3c/0x1b8 >> [ 113.969379][ T3282] el0t_64_sync_handler+0x98/0xbc >> [ 113.969980][ T3282] el0t_64_sync+0x19c/0x1a0 >> [ 113.970511][ T3282] ---[ end trace 0000000000000000 ]--- >> >> Link [1]: https://github.com/linux-test-project/ltp/blob/master/testcases/kernel/syscalls/madvise/madvise11.c >> >> Fixes: a8fc28dad6d5 ("alloc_tag: introduce clear_page_tag_ref() helper function") >> Cc: stable@vger.kernel.org # v6.10 >> Signed-off-by: Hao Ge >> --- >> mm/memory-failure.c | 6 ++++++ >> 1 file changed, 6 insertions(+) >> >> diff --git a/mm/memory-failure.c b/mm/memory-failure.c >> index 7066fc84f351..570388c41532 100644 >> --- a/mm/memory-failure.c >> +++ b/mm/memory-failure.c >> @@ -2623,6 +2623,12 @@ int unpoison_memory(unsigned long pfn) >> >> folio_put(folio); >> if (TestClearPageHWPoison(p)) { >> + /* the PG_hwpoison page will be caught and isolated >> + * on the entrance to the free buddy page pool. >> + * so,when we clear this flag and return it to the buddy system, >> + * clear it's codetag >> + */ >> + clear_page_tag_ref(p); >> folio_put(folio); >> ret = 0; >> } >> >> Thanks BR Hao