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Fri, 09 Oct 2026 06:36:22 +0000 X-Mizu-Trace-ID: a2f462b3a15301f0 X-Migadu-Flow: FLOW_OUT From: Hao Ge To: Suren Baghdasaryan , Madhavan Srinivasan , Michael Ellerman , Nicholas Piggin , "Christophe Leroy (CS GROUP)" , "Ritesh Harjani (IBM)" , Shrikanth Hegde , Alexander Potapenko , Marco Elver , Dmitry Vyukov , Andrew Morton , Dennis Zhou , Tejun Heo , Christoph Lameter , Uladzislau Rezki Cc: Hao Ge , linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com, linux-mm@kvack.org Subject: [RFC PATCH 4/4] mm/percpu: stop unmapping the CPU that failed to map Date: Fri, 9 Oct 2026 14:36:19 +0800 Message-Id: <20261009063619.112313-5-hao.ge@linux.dev> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20261009063619.112313-1-hao.ge@linux.dev> References: <20261009063619.112313-1-hao.ge@linux.dev> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 4C04FA0006 X-Stat-Signature: qnh9x31mafemz6otu18dfsanyybbsxha X-HE-Tag: 1791527784-309733 X-HE-Meta: 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 0OfrGMHd VFNR3OU4Kxr7bL2GlQkkn+/jSBBYVheke2fKGU7J6BH9UFvqCDiggNV5xaGrx8Z3Ce1kNYtGgKZGoaCIpA4nDDI9xjsicEuPf2+71A/+hPvt4ojq07gHy++MzVo2aZ3fekScY94V6gFQ9ta4eBDrIJ/B+AIN4vMTldb4qXFlSnx6ua50916MBIw0eeYwtT2gr9aYrlWwV5XUKUe8SojBf6Q4t2OeDifcda+4sa+Ua+nxenA/FKrwqu1BLpGA55SrbtVJZrkN56rTcnQ8qy9X4ayDSprAezHO0Sh42tYHCPX3Bxjg= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: __pcpu_map_pages() clears the PTEs it installed when it fails, so pcpu_map_pages() only has to tear down the CPUs it mapped before the failing one. Signed-off-by: Hao Ge --- mm/percpu-vm.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/mm/percpu-vm.c b/mm/percpu-vm.c index 509d8901835c..59d3a336a6bd 100644 --- a/mm/percpu-vm.c +++ b/mm/percpu-vm.c @@ -252,10 +252,11 @@ static int pcpu_map_pages(struct pcpu_chunk *chunk, struct page **pages, return 0; err: for_each_possible_cpu(tcpu) { - __pcpu_unmap_pages(pcpu_chunk_addr(chunk, tcpu, page_start), - page_end - page_start); + /* The failing CPU's partial mapping undoes itself */ if (tcpu == cpu) break; + __pcpu_unmap_pages(pcpu_chunk_addr(chunk, tcpu, page_start), + page_end - page_start); } pcpu_post_unmap_tlb_flush(chunk, page_start, page_end); return err; -- 2.25.1