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 27B11D2FEDB for ; Tue, 27 Jan 2026 19:30:24 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id C3CED6B0093; Tue, 27 Jan 2026 14:30:21 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id BDABA6B0095; Tue, 27 Jan 2026 14:30:21 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id B0B466B0096; Tue, 27 Jan 2026 14:30:21 -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 A066D6B0093 for ; Tue, 27 Jan 2026 14:30:21 -0500 (EST) Received: from smtpin16.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay10.hostedemail.com (Postfix) with ESMTP id 69CDBC1766 for ; Tue, 27 Jan 2026 19:30:21 +0000 (UTC) X-FDA: 84378735042.16.2A3C62D Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by imf16.hostedemail.com (Postfix) with ESMTP id B4EFF180015 for ; Tue, 27 Jan 2026 19:30:19 +0000 (UTC) Authentication-Results: imf16.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=LFjN+VuE; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf16.hostedemail.com: domain of rppt@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=rppt@kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1769542219; 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=MdC4ITwVda0lUdFB5wjfyhrvZbsNw2ij9MPQ4wY5Xmw=; b=eYFa9Dp+1sYSSijSAfrmjfvMqLFwsw3/rUL+fgAHhB1mbVAq2k9XDXkGFHDlxBD7hUaPMo 1l1H7ippunhuuJXRfcVJn7h4bXiVFa2dxt4ZIehi8/czCuzFVGD0v3C4YwyL+m5cnK/0NP VIO/AgS4OZnZ+15zndvV37vgRWk/gO8= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1769542219; a=rsa-sha256; cv=none; b=t7Tcqk13DdXf6PLDUKryA+Lk1NisCUupp2K9lK/FDgIxMDdMVK+HuR2KetoH32GPkh3WnA sJm8HY4ihG5KhGSKuQyUB9NBugymFTmL4qWpoTccuRQvwFDV1hi43Vzm142EBJ35+ZXgNL 3wHe4iu9ky+rHk0C4SLHbSoOYRrlKVI= ARC-Authentication-Results: i=1; imf16.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=LFjN+VuE; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf16.hostedemail.com: domain of rppt@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=rppt@kernel.org Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by sea.source.kernel.org (Postfix) with ESMTP id C8F694169F; Tue, 27 Jan 2026 19:30:18 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id EA1C0C116C6; Tue, 27 Jan 2026 19:30:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1769542218; bh=0i1d2fpNNGr7J2FXKMkhDUOQSLx8UrCEb1MMN67S4zY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=LFjN+VuEwQhJBIsfMbC+PmRxi9KIPVJN4uRtNpCoxNN9r9XQMLQHf0SUC/QcdqCdv yTbesD04KbeYLsqu9jsK5VCgiKMXWXlhDdWUti9o3laDuHpqKq0cyQpRIpTuVRDK3G 9s8YlgqtFbLBtQtxXOEyaDTUXUdJl17RWcVocISkGcSkSmsU5NvoiKCQikZgy87kFF O8R4uqwxHCNJdejR+L/GTxAWcoaC7L8L3E8vakXLO1fq4oq3POjF84JIKWuCS7CIvg pmavXqI0eF6TLmjO0g1n2PwhdMCDUBPPfgqRUjUwbI3BRxSmDJW4/QV6Mt7Z+eEND/ 4/xB2oNKKGPkg== 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 , Muchun Song , Nikita Kalyazin , Oscar Salvador , 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 Subject: [PATCH RFC 05/17] userfaultfd: retry copying with locks dropped in mfill_atomic_pte_copy() Date: Tue, 27 Jan 2026 21:29:24 +0200 Message-ID: <20260127192936.1250096-6-rppt@kernel.org> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20260127192936.1250096-1-rppt@kernel.org> References: <20260127192936.1250096-1-rppt@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: B4EFF180015 X-Stat-Signature: qo4cdmtcwx6enz3a9wi1tosczxp4krwb X-Rspam-User: X-Rspamd-Server: rspam02 X-HE-Tag: 1769542219-877555 X-HE-Meta: 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 OpdFzID0 tuq9IiK61Jgg6Yk3xZlDWnbP+r2iRiEGDmRIBDQSE3qni0ygdNg9cZU2THcJH7n+7QI5yH7LN+JqpWc/Wc4INwkimXGC+xtuFIIP3ogwrJjcK+/3A0pZZx2yM7hNQRYNRUM1h/r9cIorKPD2h+0Vx/MoEoOaLUVN4ELI1P3Q20gFaesULoaQeXYweSS7uDU39NQTNnDh/H+ocE7RQrB1zRWk/7xXqxNaiwaN51IjohLVYC4lRRWoPM141QW88GMJOPLLjApYq+tDgahmsG6bJvXxCQw== 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)" Implementation of UFFDIO_COPY for anonymous memory might fail to copy data data from userspace buffer when the destination VMA is locked (either with mm_lock or with per-VMA lock). In that case, mfill_atomic() releases the locks, retries copying the data with locks dropped and then re-locks the destination VMA and re-establishes PMD. Since this retry-reget dance is only relevant for UFFDIO_COPY and it never happens for other UFFDIO_ operations, make it a part of mfill_atomic_pte_copy() that actually implements UFFDIO_COPY for anonymous memory. shmem implementation will be updated later and the loop in mfill_atomic() will be adjusted afterwards. Signed-off-by: Mike Rapoport (Microsoft) --- mm/userfaultfd.c | 70 +++++++++++++++++++++++++++++++----------------- 1 file changed, 46 insertions(+), 24 deletions(-) diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c index 45d8f04aaf4f..01a2b898fa40 100644 --- a/mm/userfaultfd.c +++ b/mm/userfaultfd.c @@ -404,35 +404,57 @@ static int mfill_copy_folio_locked(struct folio *folio, unsigned long src_addr) return ret; } +static int mfill_copy_folio_retry(struct mfill_state *state, struct folio *folio) +{ + unsigned long src_addr = state->src_addr; + void *kaddr; + int err; + + /* retry copying with mm_lock dropped */ + mfill_put_vma(state); + + kaddr = kmap_local_folio(folio, 0); + err = copy_from_user(kaddr, (const void __user *) src_addr, PAGE_SIZE); + kunmap_local(kaddr); + if (unlikely(err)) + return -EFAULT; + + flush_dcache_folio(folio); + + /* reget VMA and PMD, they could change underneath us */ + err = mfill_get_vma(state); + if (err) + return err; + + err = mfill_get_pmd(state); + if (err) + return err; + + return 0; +} + static int mfill_atomic_pte_copy(struct mfill_state *state) { - struct vm_area_struct *dst_vma = state->vma; unsigned long dst_addr = state->dst_addr; unsigned long src_addr = state->src_addr; uffd_flags_t flags = state->flags; - pmd_t *dst_pmd = state->pmd; struct folio *folio; int ret; - if (!state->folio) { - ret = -ENOMEM; - folio = vma_alloc_folio(GFP_HIGHUSER_MOVABLE, 0, dst_vma, - dst_addr); - if (!folio) - goto out; + folio = vma_alloc_folio(GFP_HIGHUSER_MOVABLE, 0, state->vma, dst_addr); + if (!folio) + return -ENOMEM; - ret = mfill_copy_folio_locked(folio, src_addr); + ret = -ENOMEM; + if (mem_cgroup_charge(folio, state->vma->vm_mm, GFP_KERNEL)) + goto out_release; + ret = mfill_copy_folio_locked(folio, src_addr); + if (unlikely(ret)) { /* fallback to copy_from_user outside mmap_lock */ - if (unlikely(ret)) { - ret = -ENOENT; - state->folio = folio; - /* don't free the page */ - goto out; - } - } else { - folio = state->folio; - state->folio = NULL; + ret = mfill_copy_folio_retry(state, folio); + if (ret) + goto out_release; } /* @@ -442,17 +464,16 @@ static int mfill_atomic_pte_copy(struct mfill_state *state) */ __folio_mark_uptodate(folio); - ret = -ENOMEM; - if (mem_cgroup_charge(folio, dst_vma->vm_mm, GFP_KERNEL)) - goto out_release; - - ret = mfill_atomic_install_pte(dst_pmd, dst_vma, dst_addr, + ret = mfill_atomic_install_pte(state->pmd, state->vma, dst_addr, &folio->page, true, flags); if (ret) goto out_release; out: return ret; out_release: + /* Don't return -ENOENT so that our caller won't retry */ + if (ret == -ENOENT) + ret = -EFAULT; folio_put(folio); goto out; } @@ -907,7 +928,8 @@ static __always_inline ssize_t mfill_atomic(struct userfaultfd_ctx *ctx, break; } - mfill_put_vma(&state); + if (state.vma) + mfill_put_vma(&state); out: if (state.folio) folio_put(state.folio); -- 2.51.0