From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 4DD30CFD376 for ; Sun, 30 Nov 2025 11:18:36 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 9D0A66B000E; Sun, 30 Nov 2025 06:18:35 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 95A4A6B0010; Sun, 30 Nov 2025 06:18:35 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 849636B0011; Sun, 30 Nov 2025 06:18:35 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id 6C4076B000E for ; Sun, 30 Nov 2025 06:18:35 -0500 (EST) Received: from smtpin29.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay04.hostedemail.com (Postfix) with ESMTP id 12FC41A0C0C for ; Sun, 30 Nov 2025 11:18:35 +0000 (UTC) X-FDA: 84167025390.29.082E1AD Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by imf03.hostedemail.com (Postfix) with ESMTP id 60E5320006 for ; Sun, 30 Nov 2025 11:18:33 +0000 (UTC) Authentication-Results: imf03.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=YeR77mac; spf=pass (imf03.hostedemail.com: domain of rppt@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=rppt@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1764501513; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=FzWGSFyt0W/LS4w2Vu9AywP6exVhBuqR+qbaRna77J4=; b=yceLXNi50JfWrp/lRg5UZwGX/c62qasnwyxcFixJ0V9pLzdRpWHTaKGQSMd8E7fozvbsMR QzxxugbxsoI2NGqzFEGeQnnFAPPnACEiEzH5Ng2oXNrSkTuKzACdtRF4p+RMEOF/dUXEfW oQoMsuIIbK1PX+tRCJYZh+qQzs2WA20= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1764501513; a=rsa-sha256; cv=none; b=N9FGvZs3G2Y/czM2ASO3670tcwnQ6L0Dusf5ygJcOztiMEmXrHx5WktlHDyw3UVqNTtsri Y75bvwhqrAvCWp7AA8RBChPMbjHr9qLtkzyMesxSdELqSbNAzeyWSufLqqCdFsDdKVb65X uGLh+dpZtvnNQ6VOMIrWydviIUaN9Ko= ARC-Authentication-Results: i=1; imf03.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=YeR77mac; spf=pass (imf03.hostedemail.com: domain of rppt@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=rppt@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by sea.source.kernel.org (Postfix) with ESMTP id 9BD5A42E17; Sun, 30 Nov 2025 11:18:32 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 353A8C116D0; Sun, 30 Nov 2025 11:18:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1764501512; bh=No4OV/v0jQLoJl8PKO7GG/i2wSSVo7iZmz3MRUSzNrc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=YeR77mac03xw5SwBGRtzdZ/H+sOjspFJtYv8n6QV1GoUAtA5YBQtzB6KvA1McmoCj KG9n1DxTyB8f5KX+wIv7kufbSzy9gESul7fy+1PQlps2ZbpuCHnm//qNHYAl6rdb0g ppVz3ebKn5ThslvEpG/WIw0IQHAldkujMXFaHsjXgP69Fz5mFFnoaSO+M6Q/scZEFb zXrX8iNB+/84yNGOQcJwEYDy8DWE2tSsHnhfkHwtFBe/HSjUf9gGvwuYyXcHM6oz0c ORCVRYxO9icX1iVxjlcEPlwN8P+xjOcnQy4RUFOe38vEVO47X8Lwl16TMsJn4Sb/KE aPvK0vIq3++yA== From: Mike Rapoport To: linux-mm@kvack.org Cc: Andrea Arcangeli , Andrew Morton , Axel Rasmussen , Baolin Wang , David Hildenbrand , Hugh Dickins , James Houghton , "Liam R. Howlett" , Lorenzo Stoakes , Michal Hocko , Mike Rapoport , Nikita Kalyazin , Paolo Bonzini , Peter Xu , Sean Christopherson , Shuah Khan , Suren Baghdasaryan , Vlastimil Babka , linux-kernel@vger.kernel.org, kvm@vger.kernel.org, linux-kselftest@vger.kernel.org, "David Hildenbrand (Red Hat)" Subject: [PATCH v3 2/5] userfaultfd, shmem: use a VMA callback to handle UFFDIO_CONTINUE Date: Sun, 30 Nov 2025 13:18:09 +0200 Message-ID: <20251130111812.699259-3-rppt@kernel.org> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20251130111812.699259-1-rppt@kernel.org> References: <20251130111812.699259-1-rppt@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 60E5320006 X-Stat-Signature: tdmmnefek4ahrbjkpw4fojncgsmtu9bk X-HE-Tag: 1764501513-43947 X-HE-Meta: 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 7EU6FlKS 6ciSprVkcp5Hp9aPfLODro+AI4MeO5d2hCbkuTc1qjvrnHKxI5qZdTj/E1kOTYFE2/5d9coqPLYtIpFEVtb8gckcaRgRj0Er/o3kHN8KHTqweUbSm/dwem0BYXptSAUXuTb9g480DKqehQZZlbR8x2iXGtlef0J2Sp1LfnDCklAlhN+ssarP9UkVWF2njxLhmV/++YawSJYlkqJUST80hih7YVJOTjpGX1g23Gj/xuFLRap7a0dTRkf6Qw6fsyjTneOZiiYyysjE+uKPbSNxKHWW9NbsbFHv1qYy28kPZEpnB7BMUpM4LcXBG5rScfRecud3TEhGrifvYur6LBw2zbqlK0g== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: From: "Mike Rapoport (Microsoft)" When userspace resolves a page fault in a shmem VMA with UFFDIO_CONTINUE it needs to get a folio that already exists in the pagecache backing that VMA. Instead of using shmem_get_folio() for that, add a get_folio_noalloc() method to 'struct vm_operations_struct' that will return a folio if it exists in the VMA's pagecache at given pgoff. Implement get_folio_noalloc() method for shmem and slightly refactor userfaultfd's mfill_atomic() and mfill_atomic_pte_continue() to support this new API. Acked-by: David Hildenbrand (Red Hat) Reviewed-by: Liam R. Howlett Signed-off-by: Mike Rapoport (Microsoft) --- include/linux/mm.h | 9 ++++++++ mm/shmem.c | 18 ++++++++++++++++ mm/userfaultfd.c | 52 +++++++++++++++++++++++++++++----------------- 3 files changed, 60 insertions(+), 19 deletions(-) diff --git a/include/linux/mm.h b/include/linux/mm.h index 7c79b3369b82..6351a9cde360 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -690,6 +690,15 @@ struct vm_operations_struct { struct page *(*find_normal_page)(struct vm_area_struct *vma, unsigned long addr); #endif /* CONFIG_FIND_NORMAL_PAGE */ +#ifdef CONFIG_USERFAULTFD + /* + * Called by userfault to resolve UFFDIO_CONTINUE request. + * Should return the folio found at pgoff in the VMA's pagecache if it + * exists or ERR_PTR otherwise. + * The returned folio is locked and with reference held. + */ + struct folio *(*get_folio_noalloc)(struct inode *inode, pgoff_t pgoff); +#endif }; #ifdef CONFIG_NUMA_BALANCING diff --git a/mm/shmem.c b/mm/shmem.c index 5a3f0f754dc0..9f8c54ad0e32 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -3262,6 +3262,18 @@ int shmem_mfill_atomic_pte(pmd_t *dst_pmd, shmem_inode_unacct_blocks(inode, 1); return ret; } + +static struct folio *shmem_get_folio_noalloc(struct inode *inode, pgoff_t pgoff) +{ + struct folio *folio; + int err; + + err = shmem_get_folio(inode, pgoff, 0, &folio, SGP_NOALLOC); + if (err) + return ERR_PTR(err); + + return folio; +} #endif /* CONFIG_USERFAULTFD */ #ifdef CONFIG_TMPFS @@ -5294,6 +5306,9 @@ static const struct vm_operations_struct shmem_vm_ops = { .set_policy = shmem_set_policy, .get_policy = shmem_get_policy, #endif +#ifdef CONFIG_USERFAULTFD + .get_folio_noalloc = shmem_get_folio_noalloc, +#endif }; static const struct vm_operations_struct shmem_anon_vm_ops = { @@ -5303,6 +5318,9 @@ static const struct vm_operations_struct shmem_anon_vm_ops = { .set_policy = shmem_set_policy, .get_policy = shmem_get_policy, #endif +#ifdef CONFIG_USERFAULTFD + .get_folio_noalloc = shmem_get_folio_noalloc, +#endif }; int shmem_init_fs_context(struct fs_context *fc) diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c index 8dc964389b0d..5610f29dac73 100644 --- a/mm/userfaultfd.c +++ b/mm/userfaultfd.c @@ -388,15 +388,12 @@ static int mfill_atomic_pte_continue(pmd_t *dst_pmd, struct page *page; int ret; - ret = shmem_get_folio(inode, pgoff, 0, &folio, SGP_NOALLOC); + folio = dst_vma->vm_ops->get_folio_noalloc(inode, pgoff); /* Our caller expects us to return -EFAULT if we failed to find folio */ - if (ret == -ENOENT) - ret = -EFAULT; - if (ret) - goto out; - if (!folio) { - ret = -EFAULT; - goto out; + if (IS_ERR_OR_NULL(folio)) { + if (PTR_ERR(folio) == -ENOENT || !folio) + return -EFAULT; + return PTR_ERR(folio); } page = folio_file_page(folio, pgoff); @@ -411,13 +408,12 @@ static int mfill_atomic_pte_continue(pmd_t *dst_pmd, goto out_release; folio_unlock(folio); - ret = 0; -out: - return ret; + return 0; + out_release: folio_unlock(folio); folio_put(folio); - goto out; + return ret; } /* Handles UFFDIO_POISON for all non-hugetlb VMAs. */ @@ -694,6 +690,15 @@ static __always_inline ssize_t mfill_atomic_pte(pmd_t *dst_pmd, return err; } +static __always_inline bool vma_can_mfill_atomic(struct vm_area_struct *vma, + uffd_flags_t flags) +{ + if (uffd_flags_mode_is(flags, MFILL_ATOMIC_CONTINUE)) + return vma->vm_ops && vma->vm_ops->get_folio_noalloc; + + return vma_is_anonymous(vma) || vma_is_shmem(vma); +} + static __always_inline ssize_t mfill_atomic(struct userfaultfd_ctx *ctx, unsigned long dst_start, unsigned long src_start, @@ -766,10 +771,7 @@ static __always_inline ssize_t mfill_atomic(struct userfaultfd_ctx *ctx, return mfill_atomic_hugetlb(ctx, dst_vma, dst_start, src_start, len, flags); - if (!vma_is_anonymous(dst_vma) && !vma_is_shmem(dst_vma)) - goto out_unlock; - if (!vma_is_shmem(dst_vma) && - uffd_flags_mode_is(flags, MFILL_ATOMIC_CONTINUE)) + if (!vma_can_mfill_atomic(dst_vma, flags)) goto out_unlock; while (src_addr < src_start + len) { @@ -1985,9 +1987,21 @@ bool vma_can_userfault(struct vm_area_struct *vma, vm_flags_t vm_flags, if (vma->vm_flags & VM_DROPPABLE) return false; - if ((vm_flags & VM_UFFD_MINOR) && - (!is_vm_hugetlb_page(vma) && !vma_is_shmem(vma))) - return false; + if (vm_flags & VM_UFFD_MINOR) { + /* + * If only MINOR mode is requested and we can request an + * existing folio from VMA's page cache, allow it + */ + if (vm_flags == VM_UFFD_MINOR && vma->vm_ops && + vma->vm_ops->get_folio_noalloc) + return true; + /* + * Only hugetlb and shmem can support MINOR mode in combination + * with other modes + */ + if (!is_vm_hugetlb_page(vma) && !vma_is_shmem(vma)) + return false; + } /* * If wp async enabled, and WP is the only mode enabled, allow any -- 2.51.0