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Thu, 03 Sep 2026 05:21:52 -0700 (PDT) From: Muchun Song To: Andrew Morton , Dan Williams , David Hildenbrand Cc: 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 , Muchun Song , muchun.song@linux.dev Subject: [PATCH 2/4] nvdimm/pmem: avoid HWPoison flag updates for clean pages Date: Thu, 3 Sep 2026 20:21:25 +0800 Message-ID: <20260903122128.12264-3-songmuchun@bytedance.com> X-Mailer: git-send-email 2.54.0 In-Reply-To: <20260903122128.12264-1-songmuchun@bytedance.com> References: <20260903122128.12264-1-songmuchun@bytedance.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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. 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. 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. Signed-off-by: Muchun Song --- drivers/nvdimm/pmem.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c index 30a51c365ce8..b14f75daeda7 100644 --- a/drivers/nvdimm/pmem.c +++ b/drivers/nvdimm/pmem.c @@ -80,7 +80,7 @@ static void pmem_mkpage_present(struct pmem_device *pmem, phys_addr_t offset, * here since we're in the driver I/O path and * outstanding I/O requests pin the dev_pagemap. */ - if (test_and_clear_pmem_poison(page)) + if (PageHWPoison(page) && test_and_clear_pmem_poison(page)) clear_mce_nospec(pfn); } } -- 2.54.0