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 A379FCC6B01 for ; Thu, 2 Apr 2026 04:13:04 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 122606B009F; Thu, 2 Apr 2026 00:13:04 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 0F9F66B00A1; Thu, 2 Apr 2026 00:13:04 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 036BC6B00A2; Thu, 2 Apr 2026 00:13:03 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0010.hostedemail.com [216.40.44.10]) by kanga.kvack.org (Postfix) with ESMTP id E92FC6B009F for ; Thu, 2 Apr 2026 00:13:03 -0400 (EDT) Received: from smtpin30.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay09.hostedemail.com (Postfix) with ESMTP id B16B18B7B8 for ; Thu, 2 Apr 2026 04:13:03 +0000 (UTC) X-FDA: 84612295446.30.5616D8B Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by imf13.hostedemail.com (Postfix) with ESMTP id 084B520007 for ; Thu, 2 Apr 2026 04:13:01 +0000 (UTC) Authentication-Results: imf13.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=NIZNqIdp; spf=pass (imf13.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-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1775103182; a=rsa-sha256; cv=none; b=OouN+MSmmiA92nLjdnjXsefPwZJHcotZohAr5pg8m9hZaSKpk5aTbkaOeIJrV0SCgBXzVB 6dXk5zbmvi9ycDuvn2eeJEGathL1D2qH2aKTmfP7ij7hq5hyeZk2vaeSi89R44xhbeuEKm MG9iz7jWTOGh2neLy/cCWZE0rE7Tbtw= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1775103182; 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=b3O3nTbzGihVtxjjI/2f4S+asSKC/YGLteudu0vZgmM=; b=BNptT+P61bPwrpdHVNrhHTUSbUs5nvyuHTWpzAipHtog87wHJO5uYTDllcft2X1/9EWFkg ssi34LdIJPnzVsC6OzsUuO2MbL3YNQg47QROsYnXTrxX73+t01/F6RxxtqshHWVVqSyIAJ mkLHMRaNOoAmKuTszV/2Lwm0Ssh6LEU= ARC-Authentication-Results: i=1; imf13.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=NIZNqIdp; spf=pass (imf13.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 23E9B437D5; Thu, 2 Apr 2026 04:13:01 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id B74D5C19423; Thu, 2 Apr 2026 04:12:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1775103181; bh=lxXvlQh8xQ0EBf3to4Jw9wikE7NXPrSIjYbQ7Uoyt4w=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=NIZNqIdpzm6+W6HPk4rUKciovxte+Ir8R8/epNSPXK4ip3mfFRx//HB3VsV4IcxxY grhk26iS3k+sEk5UN3RQPGXSmhhMYLSeaXHgHVluotjZ6QucMngudS0xvMQNTYyXnd fPX67hTxkQB0+QkM0QhDxLlU5z8oq1o45ObGQwWRFVtkvVRHiPuW5c45f/knY49Lxo bz+Svo6RhYvPkYQaPWYDCZy5cAXqxiuCP3BS1sV6yFr0lF3y+Fv8D/EX7kM03kDhdP d6LWFm8CkHHdTroVD7ewqX5/jlazhuinnayqlFjpEcdv3LiuGb8upVQNvMeIAdvlqF nsIyaZ2SbjyKg== From: Mike Rapoport To: Andrew Morton Cc: Andrea Arcangeli , Andrei Vagin , Axel Rasmussen , Baolin Wang , David Hildenbrand , Harry Yoo , Hugh Dickins , James Houghton , "Liam R. Howlett" , "Lorenzo Stoakes (Oracle)" , "Matthew Wilcox (Oracle)" , Michal Hocko , Mike Rapoport , Muchun Song , Nikita Kalyazin , Oscar Salvador , Paolo Bonzini , Peter Xu , Sean Christopherson , Shuah Khan , Suren Baghdasaryan , Vlastimil Babka , kvm@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-mm@kvack.org Subject: [PATCH v4 08/15] shmem, userfaultfd: use a VMA callback to handle UFFDIO_CONTINUE Date: Thu, 2 Apr 2026 07:11:49 +0300 Message-ID: <20260402041156.1377214-9-rppt@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260402041156.1377214-1-rppt@kernel.org> References: <20260402041156.1377214-1-rppt@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 084B520007 X-Stat-Signature: pe1cmuig9b4de3u49p1zehwuudhii7fk X-HE-Tag: 1775103181-487897 X-HE-Meta: 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 jGXuEB8B OzWR0X0/O4m/5W6RWkkA15kSnuyaC9so+rGTENQStVw6iq3JLfNgBCEG5GFTGuE5NZy50SSg+/bhPTgjtg/rWK6FAEX9dZDS6gKCLVHLkDmK1MYoUX676aBrTIycXCXAvcky5W00K6mIrgCREpL4wnTEc49Zztl0avIheJ6rVcEcrckIzA4Tr+xyEhb0mH2MBwKzuJP/NaXqcMEA3VUsNtSKUrTTOgCNyc+vRacgsLdwsL1GphDT8/9DCnwjGrjr8AJRpvoN+9Lee6zcLx/t67EaWOOXBvNO4k7Ah0LMrKa/JKel2xC4EFpYe7w== 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_uffd_ops' 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_get_vma() and mfill_atomic_pte_continue() to support this new API. Signed-off-by: Mike Rapoport (Microsoft) Reviewed-by: James Houghton --- include/linux/userfaultfd_k.h | 7 +++++++ mm/shmem.c | 15 ++++++++++++++- mm/userfaultfd.c | 34 ++++++++++++++++++---------------- 3 files changed, 39 insertions(+), 17 deletions(-) diff --git a/include/linux/userfaultfd_k.h b/include/linux/userfaultfd_k.h index 56e85ab166c7..66dfc3c164e6 100644 --- a/include/linux/userfaultfd_k.h +++ b/include/linux/userfaultfd_k.h @@ -84,6 +84,13 @@ extern vm_fault_t handle_userfault(struct vm_fault *vmf, unsigned long reason); struct vm_uffd_ops { /* Checks if a VMA can support userfaultfd */ bool (*can_userfault)(struct vm_area_struct *vma, vm_flags_t vm_flags); + /* + * Called 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); }; /* A combined operation mode + behavior flags. */ diff --git a/mm/shmem.c b/mm/shmem.c index f2a25805b9bf..7bd887b64f62 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -3295,13 +3295,26 @@ int shmem_mfill_atomic_pte(pmd_t *dst_pmd, 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; +} + static bool shmem_can_userfault(struct vm_area_struct *vma, vm_flags_t vm_flags) { return true; } static const struct vm_uffd_ops shmem_uffd_ops = { - .can_userfault = shmem_can_userfault, + .can_userfault = shmem_can_userfault, + .get_folio_noalloc = shmem_get_folio_noalloc, }; #endif /* CONFIG_USERFAULTFD */ diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c index e3024a39c19d..832dbdde5868 100644 --- a/mm/userfaultfd.c +++ b/mm/userfaultfd.c @@ -191,6 +191,7 @@ static int mfill_get_vma(struct mfill_state *state) struct userfaultfd_ctx *ctx = state->ctx; uffd_flags_t flags = state->flags; struct vm_area_struct *dst_vma; + const struct vm_uffd_ops *ops; int err; /* @@ -232,10 +233,12 @@ static int mfill_get_vma(struct mfill_state *state) if (is_vm_hugetlb_page(dst_vma)) return 0; - if (!vma_is_anonymous(dst_vma) && !vma_is_shmem(dst_vma)) + ops = vma_uffd_ops(dst_vma); + if (!ops) goto out_unlock; - if (!vma_is_shmem(dst_vma) && - uffd_flags_mode_is(flags, MFILL_ATOMIC_CONTINUE)) + + if (uffd_flags_mode_is(flags, MFILL_ATOMIC_CONTINUE) && + !ops->get_folio_noalloc) goto out_unlock; return 0; @@ -575,6 +578,7 @@ static int mfill_atomic_pte_zeropage(struct mfill_state *state) static int mfill_atomic_pte_continue(struct mfill_state *state) { struct vm_area_struct *dst_vma = state->vma; + const struct vm_uffd_ops *ops = vma_uffd_ops(dst_vma); unsigned long dst_addr = state->dst_addr; pgoff_t pgoff = linear_page_index(dst_vma, dst_addr); struct inode *inode = file_inode(dst_vma->vm_file); @@ -584,17 +588,16 @@ static int mfill_atomic_pte_continue(struct mfill_state *state) struct page *page; int ret; - ret = shmem_get_folio(inode, pgoff, 0, &folio, SGP_NOALLOC); - /* 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 (!ops) { + VM_WARN_ONCE(1, "UFFDIO_CONTINUE for unsupported VMA"); + return -EOPNOTSUPP; } + folio = ops->get_folio_noalloc(inode, pgoff); + /* Our caller expects us to return -EFAULT if we failed to find folio */ + if (IS_ERR_OR_NULL(folio)) + return -EFAULT; + page = folio_file_page(folio, pgoff); if (PageHWPoison(page)) { ret = -EIO; @@ -607,13 +610,12 @@ static int mfill_atomic_pte_continue(struct mfill_state *state) 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. */ -- 2.53.0