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Tue, 22 Sep 2026 02:34:11 +0000 X-Mizu-Trace-ID: 8af55bfa8c8b6846 X-Migadu-Flow: FLOW_OUT Content-Type: text/plain; charset=us-ascii Mime-Version: 1.0 (Mac OS X Mail 16.0 \(3864.700.51.1.1\)) Subject: Re: [PATCH 2/4] nvdimm/pmem: avoid HWPoison flag updates for clean pages From: Muchun Song In-Reply-To: Date: Tue, 22 Sep 2026 10:33:54 +0800 Cc: Muchun Song , Andrew Morton , Dan Williams , David Hildenbrand , linux-mm@kvack.org, nvdimm@lists.linux.dev, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-cxl@vger.kernel.org, Vishal Verma , Dave Jiang , Alison Schofield , Mike Rapoport , Oscar Salvador , Ira Weiny , Jan Kara , Matthew Wilcox , Lorenzo Stoakes , Vlastimil Babka , Michal Hocko , Qi Zheng Content-Transfer-Encoding: quoted-printable Message-Id: References: <20260903122128.12264-1-songmuchun@bytedance.com> <20260903122128.12264-3-songmuchun@bytedance.com> To: "Oscar Salvador (SUSE)" X-Mailer: Apple Mail (2.3864.700.51.1.1) X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: D96BB180006 X-Stat-Signature: wcritesrm4ymsqmgcfp49n6fret73jmu X-Rspam-User: X-HE-Tag: 1790044455-110869 X-HE-Meta: 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 cCKt2/gj 16bgjSIm+ML2SdwIwVWck0iYoOtVY/xj3QJ19JLFhxhchr3nWQIWBHNVwCFqUSeGq4Y+7knZID3EIYuZN2vRMWKr579doI03+oupMZBrJfrTpV/e6MpAWd031YtPtFYsAdzE0YcfWDAXpvx64f4eaLD19XW0EYEUyNYdq7CMR9p6vkulkHqTVQ7Rvj6WYv8Tnrg8cO/ADXLSgARIH3ZCbARryAduwt/bgWtjZe1dBpfenaE4TUHt343JptWYY32yAbKEbqdNhFjQU0tuI36oOkWZYhnTnB5eIxl85iUdl5tvoeoQnaGPtEVvwjQ== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: > On Sep 21, 2026, at 20:53, Oscar Salvador (SUSE) = wrote: >=20 > On Thu, Sep 03, 2026 at 08:21:25PM +0800, Muchun Song wrote: >> pmem_mkpage_present() is called after persistent-memory poison has = been >> cleared. It only needs to clear PG_hwpoison and undo the MCE nospec = state >> for PFNs that are still marked poisoned. >>=20 >> For clean PFNs, test_and_clear_pmem_poison() has no semantic effect, = but it >> still performs an atomic clear operation against struct page flags. = That is >> unnecessary today and conflicts with the FS-DAX vmemmap optimization = added >> later in the series, where clean PFNs may be backed by shared = read-only >> metadata. >>=20 >> Check PageHWPoison() first so only poisoned PFNs update the page = state. >> Poison recovery keeps the same behavior, while clean PFNs no longer = require >> writable per-PFN metadata. >>=20 >> Signed-off-by: Muchun Song >=20 > Then change itself looks good to me, so >=20 > Reviewed-by: Oscar Salvador Thanks for your review. >=20 > but any reason not to hide the PageHWPoison check within = test_and_clear_pmem_poison()? I indeed hadn't considered this point before. But now I find it unnecessary, because a patch [1] has already removed = test_and_clear_pmem_poison(). [1] = https://lore.kernel.org/all/20260903053535.17611-3-kaitao.cheng@linux.dev/= Thanks, Muchun >=20 >=20 >=20 > --=20 > Oscar Salvador > SUSE Labs