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t=1794753592; bh=VUhc9pkYOrY2WKIFmAXqR2xKENpkrWiHDZ6moy3jlKU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=UUCl9VrXF/3pSiQcdOiLwRcj2glPTciruxq0WAPAQq820l5y7LsY1IGsnlL7bIXrL nLjmrGgzs0iIo0wvtTBTuXjcOi9IbHXIEqFBtWoYi4U1UHjA6LcFRrjex7wTMR0JVd UX0x3sXOqQRtmQ4b5NIgPqmoey+ELvB7Wfs/CyPU= From: Dev Jain To: david@kernel.org, ljs@kernel.org, akpm@linux-foundation.org, hughd@google.com, chrisl@kernel.org, kasong@tencent.com, davem@davemloft.net, andreas@gaisler.com Cc: Dev Jain , riel@surriel.com, liam@infradead.org, vbabka@kernel.org, harry@kernel.org, jannh@google.com, lance.yang@linux.dev, baolin.wang@linux.alibaba.com, shikemeng@huaweicloud.com, nphamcs@gmail.com, baoquan.he@linux.dev, baohua@kernel.org, youngjun.park@lge.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, rppt@kernel.org, surenb@google.com, mhocko@suse.com, pfalcato@suse.de, anshuman.khandual@arm.com, geert@linux-m68k.org, sparclinux@vger.kernel.org, ryan.roberts@arm.com Subject: [PATCH v4 4/9] mm/rmap: Add batched version of folio_try_share_anon_rmap_pte Date: Sun, 15 Nov 2026 14:38:59 +0000 Message-ID: <20261115143905.3045084-5-dev.jain@arm.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20261115143905.3045084-1-dev.jain@arm.com> References: <20261115143905.3045084-1-dev.jain@arm.com> X-Archived-By: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Stat-Signature: hdkbbf71fuwb6wuy7q3croshmce6t4q9 X-Rspamd-Server: rspam01 X-Rspam-User: X-Spam-Status: No, score=-18.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_PASS, SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=4.0.1 X-Rspamd-Queue-Id: BADB910000A X-HE-Tag: 1794753593-182406 X-HE-Meta: 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 b6lpIhhA TozNTeGfLXOSXLsb2uKkTqwmWDlVsrJhXdeQHloPXXqqWNgG28msm4xch2PfE2pIiCppH8q+pAb9NiHo1C5CuekIcMAvMIMGc6of0agBayw7lEfxVSuPaFWUvNXkYVlvrS2WKiA7jdiGQJDlzvOJDqWs4OORG9udz4e5PKqFfPcGynkDwpIV0KzG9RnLXwxiNDT2OmkZnIM+d/gh2B8ZJKL0EIzSl+zwWpiI8kQVzih4ZrpwbV0EvIQ1OfSExZTDTwfvA7ewddhHH+uwELUTCu5ASfvAovMCAU7YOpOpv2+Hl9eoumIeXUUi/y7LqWR2nSiUn Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 To enable batched unmapping of anonymous folios, we need to handle the sharing of exclusive pages. Hence, a batched version of folio_try_share_anon_rmap_pte is required. Currently, the sole purpose of nr_pages in __folio_try_share_anon_rmap is to do some rmap sanity checks. Now, clear the PageAnonExclusive bit on a batch of nr_pages. Refactor the function such that the clearing of the bit can be done at one place without duplication. Note that __folio_try_share_anon_rmap can receive nr_pages == HPAGE_PMD_NR from the PMD path, but currently we only clear the bit on the head page. Retain this behaviour by setting nr_pages = 1 in case the caller is folio_try_share_anon_rmap_pmd. While at it, convert nr_pages to unsigned long to future-proof from overflow in case P4D-huge mappings etc get supported down the road. I haven't made such a change in each function receiving nr_pages in try_to_unmap_one - perhaps this can be done incrementally. Add two WARN's: check that the batch is entirely exclusive (for PMD callers, need to check only head page), and that there are only PTE/PMD paths converging into __folio_try_share_anon_rmap. Reviewed-by: Barry Song Signed-off-by: Dev Jain --- include/linux/rmap.h | 58 +++++++++++++++++++++++++++++++------------- 1 file changed, 41 insertions(+), 17 deletions(-) diff --git a/include/linux/rmap.h b/include/linux/rmap.h index 43d6bbecd2fab..f4ffbc60b3859 100644 --- a/include/linux/rmap.h +++ b/include/linux/rmap.h @@ -724,17 +724,25 @@ static inline int folio_try_dup_anon_rmap_pmd(struct folio *folio, } static __always_inline int __folio_try_share_anon_rmap(struct folio *folio, - struct page *page, int nr_pages, enum pgtable_level level) + struct page *page, unsigned long nr_pages, enum pgtable_level level) { + /* device private folios cannot get pinned via GUP. */ + const bool pinnable = !folio_is_device_private(folio); + bool exclusive __maybe_unused; + VM_WARN_ON_FOLIO(!folio_test_anon(folio), folio); VM_WARN_ON_FOLIO(!PageAnonExclusive(page), folio); + __folio_rmap_sanity_checks(folio, page, nr_pages, level); - /* device private folios cannot get pinned via GUP. */ - if (unlikely(folio_is_device_private(folio))) { - ClearPageAnonExclusive(page); - return 0; - } + VM_WARN_ON_ONCE(level != PGTABLE_LEVEL_PTE && level != PGTABLE_LEVEL_PMD); + + /* We only clear anon-exclusive from head page of PMD folio. */ + if (level == PGTABLE_LEVEL_PMD) + nr_pages = 1; + + VM_WARN_ON_FOLIO(page_anon_exclusive_batch(0, nr_pages, page, + &exclusive) != nr_pages, folio); /* * We have to make sure that when we clear PageAnonExclusive, that @@ -778,29 +786,38 @@ static __always_inline int __folio_try_share_anon_rmap(struct folio *folio, * so we use explicit ones here. */ - /* Paired with the memory barrier in try_grab_folio(). */ - if (IS_ENABLED(CONFIG_HAVE_GUP_FAST)) - smp_mb(); + if (likely(pinnable)) { + /* Paired with the memory barrier in try_grab_folio(). */ + if (IS_ENABLED(CONFIG_HAVE_GUP_FAST)) + smp_mb(); - if (unlikely(folio_maybe_dma_pinned(folio))) - return -EBUSY; - ClearPageAnonExclusive(page); + if (unlikely(folio_maybe_dma_pinned(folio))) + return -EBUSY; + } + + for (;;) { + ClearPageAnonExclusive(page); + if (--nr_pages == 0) + break; + page++; + } /* * This is conceptually a smp_wmb() paired with the smp_rmb() in * gup_must_unshare(). */ - if (IS_ENABLED(CONFIG_HAVE_GUP_FAST)) + if (likely(pinnable) && IS_ENABLED(CONFIG_HAVE_GUP_FAST)) smp_mb__after_atomic(); return 0; } /** - * folio_try_share_anon_rmap_pte - try marking an exclusive anonymous page - * mapped by a PTE possibly shared to prepare + * folio_try_share_anon_rmap_ptes - try marking exclusive anonymous pages + * mapped by PTEs possibly shared to prepare * for KSM or temporary unmapping * @folio: The folio to share a mapping of - * @page: The mapped exclusive page + * @page: The first mapped exclusive page of the batch in the folio + * @nr_pages: The number of pages to share in the folio (batch size) * * The caller needs to hold the page table lock and has to have the page table * entries cleared/invalidated. @@ -816,10 +833,17 @@ static __always_inline int __folio_try_share_anon_rmap(struct folio *folio, * Returns 0 if marking the mapped page possibly shared succeeded. Returns * -EBUSY otherwise. */ +static inline int folio_try_share_anon_rmap_ptes(struct folio *folio, + struct page *page, unsigned long nr_pages) +{ + return __folio_try_share_anon_rmap(folio, page, nr_pages, + PGTABLE_LEVEL_PTE); +} + static inline int folio_try_share_anon_rmap_pte(struct folio *folio, struct page *page) { - return __folio_try_share_anon_rmap(folio, page, 1, PGTABLE_LEVEL_PTE); + return folio_try_share_anon_rmap_ptes(folio, page, 1); } /** -- 2.43.0