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h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=ibIf8yAHfrhdjxWvrAS5TzBxXi6L6v1hS0RK2Etic5vYyGqEkiVuUD/KzF4GbrNLC 2sehhKkGT3UcwwKb7EOE/371CgMTnoB99WjWg/4ShdQt06ikxp96YxwMCgP8cVFUrI nkWjNoaWLjEG9Q7z19lZruZXLRl0n48r+4p8qLhY= From: Dev Jain To: akpm@linux-foundation.org, david@kernel.org, ljs@kernel.org, chrisl@kernel.org, kasong@tencent.com, hughd@google.com, liam@infradead.org Cc: Dev Jain , riel@surriel.com, vbabka@kernel.org, harry@kernel.org, jannh@google.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, rppt@kernel.org, surenb@google.com, mhocko@suse.com, qi.zheng@linux.dev, shakeel.butt@linux.dev, baohua@kernel.org, axelrasmussen@google.com, yuanchu@google.com, weixugc@google.com, shikemeng@huaweicloud.com, nphamcs@gmail.com, bhe@redhat.com, youngjun.park@lge.com, baolin.wang@linux.alibaba.com, pfalcato@suse.de, ryan.roberts@arm.com, anshuman.khandual@arm.com Subject: [PATCH v4 09/12] mm/rmap: Add batched version of folio_try_share_anon_rmap_pte Date: Tue, 26 May 2026 12:06:32 +0530 Message-Id: <20260526063635.61721-10-dev.jain@arm.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20260526063635.61721-1-dev.jain@arm.com> References: <20260526063635.61721-1-dev.jain@arm.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam11 X-Stat-Signature: hg8zp4d9hetfwazypxyazn6try65tdz3 X-Rspamd-Queue-Id: 49C5BC0002 X-Rspam-User: X-HE-Tag: 1779777507-719457 X-HE-Meta: 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 SvOk9YEu baEPT0nWAaU45j744PwMcFRraYYd1lOjGcT282tcaSzeQ3tzjfl4ETxDbUcd3xJne7GIbFhvLBwWhSK0sTDM4LFhpYaMxTehv7BwfwSYYiz37VaIJWIiG9XIpANgZSaaLAzYG+ugEECpfQ8bE23/17TMOYMHKo2AkGxdyLOSMvNYTyLgSbYvBkkTyVAN52wtW3J73a0l4R9BH63cpPgZB+IOb1WI+EeoTNh2zE5T2AmxQ3lDOVADEfZ0occ2fkMGUCPKkWQMV987zUm/FP2G2j9bAQXsExvRcDRlf Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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. Signed-off-by: Dev Jain --- include/linux/rmap.h | 52 +++++++++++++++++++++++++++++--------------- 1 file changed, 35 insertions(+), 17 deletions(-) diff --git a/include/linux/rmap.h b/include/linux/rmap.h index 8dc0871e5f001..64929490a7cfc 100644 --- a/include/linux/rmap.h +++ b/include/linux/rmap.h @@ -706,17 +706,18 @@ 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 = likely(!folio_is_device_private(folio)); + 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; - } + /* We only clear anon-exclusive from head page of PMD folio */ + if (level == PGTABLE_LEVEL_PMD) + nr_pages = 1; /* * We have to make sure that when we clear PageAnonExclusive, that @@ -760,29 +761,38 @@ 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 (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 (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. @@ -797,11 +807,19 @@ 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. + * + * The caller needs to hold the page table lock. */ +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); } /** -- 2.34.1