From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 3339F39524B for ; Tue, 26 May 2026 06:38:26 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779777509; cv=none; b=hmea4rF9QcXgvwKMiF6sDJEwXM7qN36p7kQhQx0JrxZLAIBOLloeMsQVZ4iVNVjl/CRviEvh5pxGBNHJr+dvRG4/3ZHCiUcKIqNqBwl0vHvGNYWrb6+Zq+YRkCd8KboepG/vbDhGkt5AGVcCJjq1JXuq7UeicgOnWCZep8GBF/Q= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779777509; c=relaxed/simple; bh=Gvx/Kb5XuiTOgCvken+/31zz+LIsv8TKngc1TMiafk8=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=c9H0C/GzfmJy3bR0YWsk6yhoKOZjhx57GObhB9GKxdQg8AEHPERke+mteNoGJ+sTBJdPOJ+60kB0/HR7sTBhZuvd8Z7TLzJmo6yZMMXpwHZ1NV9fg5IoDWXh7uDax7mPA7zY0JzAm90e+YqNGpWeuNF2RSF00u+xCpnaMfCD9KQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b=ibIf8yAH; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b="ibIf8yAH" Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 78ADD22FC; Mon, 25 May 2026 23:38:21 -0700 (PDT) Received: from a080796.blr.arm.com (a080796.arm.com [10.164.21.51]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id D98683F7D8; Mon, 25 May 2026 23:38:16 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1779777506; bh=Gvx/Kb5XuiTOgCvken+/31zz+LIsv8TKngc1TMiafk8=; 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> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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