From patchwork Mon Jan 29 19:35:12 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Lokesh Gidra X-Patchwork-Id: 193680 Return-Path: Delivered-To: ouuuleilei@gmail.com Received: by 2002:a05:7301:2087:b0:106:209c:c626 with SMTP id gs7csp792509dyb; Mon, 29 Jan 2024 11:43:01 -0800 (PST) X-Google-Smtp-Source: AGHT+IGlyxMpOZ9M56WZC/u6P4pDeC3vDGPV97cf6+04Tzaihi0SAKu8UMy4kZ0ilHi3OAgF29tz X-Received: by 2002:a17:903:2615:b0:1d7:691e:2707 with SMTP id jd21-20020a170903261500b001d7691e2707mr3830830plb.27.1706557381084; Mon, 29 Jan 2024 11:43:01 -0800 (PST) ARC-Seal: i=2; a=rsa-sha256; t=1706557381; cv=pass; d=google.com; s=arc-20160816; b=kbfKqIKd4WdOotsUJ45dRVefrAiLdjxBurv6vsMBBCkN/1b+ao+r9vdDxt3hW0h5Xu ejkF9qDvonUO6hv4ZL2SUon0D7d0q3pNhuY6t5QJcxEtVEcbt3ShPBa+XM5u3DROnQRT wR+AoHRStbF2VlEVnZzDgk7v1/i5WsHAmcpjsUHMPbVMIFtoGQ5ob3oZqDBX0ArJWg7j GRr1xS2tpMu4Zcn0n651eUo8BWg2y9nMZKZjq41vxDLW8hKoUazxtW2N3oh5DqQ/IrOq GtGxubKjBXeI1ILN4nmL7PfaCi4pM5M+qfmgI1ydSfPYzfogs9jWzby9usHToFnQBZr5 j3IA== ARC-Message-Signature: i=2; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=cc:to:from:subject:message-id:references:mime-version :list-unsubscribe:list-subscribe:list-id:precedence:in-reply-to:date :dkim-signature; bh=/rTTdTkZrF1wexi3aiNZ7/0XWdKeqDeZCcom0yepX1o=; fh=YpYg+AMOLH4GRgVOvnwFLenCYLn09uoxMCo5ibUfZzo=; b=KxBjnxO7g9u5elX+MYjhO5n/FqIXUFlRp9dXByeQBaJHwU8GLPkoTCdP/TteNvkklv SHoRypOQM/RPTNcGdCINkd6Od8ZFtNm6oLPUn9ik5etb9YRNbiwQliSg4Qw4Fh4cXCIP rE6U/IoZhpz7nPOY7Wp1y98BjDP7g+V6cuKc5/t38dpfPQ3Fkzv5J0YOzt5PSY4QRxqh 4myP4UH0y9n5mdLiFJel7sTFYHIbqBU53VoaKaESeU4V8yGqU9Yw7aH6v6gjSb3OCulj IwMPkOzBooiJwaBpVODJWFxjdpFW7+rW5Ap992kLQy6/JTNngXndypTm+fWLGLzcWBh0 6VUw== ARC-Authentication-Results: i=2; mx.google.com; dkim=pass header.i=@google.com header.s=20230601 header.b=xKqYfZQq; arc=pass (i=1 spf=pass spfdomain=flex--lokeshgidra.bounces.google.com dkim=pass dkdomain=google.com dmarc=pass fromdomain=google.com); spf=pass (google.com: domain of linux-kernel+bounces-43420-ouuuleilei=gmail.com@vger.kernel.org designates 2604:1380:40f1:3f00::1 as permitted sender) smtp.mailfrom="linux-kernel+bounces-43420-ouuuleilei=gmail.com@vger.kernel.org"; dmarc=pass (p=REJECT sp=REJECT dis=NONE) header.from=google.com Received: from sy.mirrors.kernel.org (sy.mirrors.kernel.org. [2604:1380:40f1:3f00::1]) by mx.google.com with ESMTPS id ks2-20020a056a004b8200b006d99ed4ae9fsi6029978pfb.8.2024.01.29.11.43.00 for (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 29 Jan 2024 11:43:01 -0800 (PST) Received-SPF: pass (google.com: domain of linux-kernel+bounces-43420-ouuuleilei=gmail.com@vger.kernel.org designates 2604:1380:40f1:3f00::1 as permitted sender) client-ip=2604:1380:40f1:3f00::1; Authentication-Results: mx.google.com; dkim=pass header.i=@google.com header.s=20230601 header.b=xKqYfZQq; arc=pass (i=1 spf=pass spfdomain=flex--lokeshgidra.bounces.google.com dkim=pass dkdomain=google.com dmarc=pass fromdomain=google.com); spf=pass (google.com: domain of linux-kernel+bounces-43420-ouuuleilei=gmail.com@vger.kernel.org designates 2604:1380:40f1:3f00::1 as permitted sender) smtp.mailfrom="linux-kernel+bounces-43420-ouuuleilei=gmail.com@vger.kernel.org"; dmarc=pass (p=REJECT sp=REJECT dis=NONE) header.from=google.com Received: from smtp.subspace.kernel.org (wormhole.subspace.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by sy.mirrors.kernel.org (Postfix) with ESMTPS id 7FE7DB25830 for ; Mon, 29 Jan 2024 19:36:55 +0000 (UTC) Received: from localhost.localdomain (localhost.localdomain [127.0.0.1]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 497AA157E66; Mon, 29 Jan 2024 19:35:45 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="xKqYfZQq" Received: from mail-yb1-f202.google.com (mail-yb1-f202.google.com [209.85.219.202]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 7369F1552F2 for ; Mon, 29 Jan 2024 19:35:37 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.219.202 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1706556940; cv=none; b=Tp1ACQxX0OJc73q/aym5B2fQ4nGxJ4HR26FaCIE2zGUpFbvRbzsJK6R6abmbCszLtapPwc24PepY0SFjDvbzCj6nLdJAbopOs211Pf1vz/dFT2ZEMk1hiNBWXyTaXwz1y3bfHST4BRatCVp8g2Vu29PcK1gUFZPizPOTaSH1+KA= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1706556940; c=relaxed/simple; bh=+HdbbaQZa8+A0lATLROmSrWayDBc8cSfyhmoQJXBCs8=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=m3fch7pzYQ3w6TdmZcDR7TrFQqkmfDMn/kQstTUB00gB2h4fF+8C8AV5zvu2Iefqymjqppj/B5V7wKavKHQbWBMwX6PwnCFBpBRZcqRCd4FwRDTTPAxgZscsvWwvay33LGIa0cy4JLiYyRMepGxY7QQvyk4+Zo9chZnpS2Wyun8= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--lokeshgidra.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=xKqYfZQq; arc=none smtp.client-ip=209.85.219.202 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--lokeshgidra.bounces.google.com Received: by mail-yb1-f202.google.com with SMTP id 3f1490d57ef6-dc265e7a67cso5381174276.0 for ; Mon, 29 Jan 2024 11:35:37 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1706556936; x=1707161736; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=/rTTdTkZrF1wexi3aiNZ7/0XWdKeqDeZCcom0yepX1o=; b=xKqYfZQq1gwh+Hwvnyx8H8UOCQVCqg+uLZGLmvDznYQtjy6KAv1iQ4zydpQd/ucLUc iEt7a6rGibfEbm/wAldZJcHq0M1qF6XjN8frVZAxLVLUGX4a6t439GrENNxxrlxCNRCL 5+YHF+i34KUUmaWxtObdkPcjaBHIPQxJ2WKeDreKZ4XgVMrYSIggqOrVDNKlt7T9fL5W A0/MHsiPaktsqVoTCfDFKhUZVnbsEpqYSqkeU3Nxe6XfZWhVlli70K1a/qZbW4jw8cxh R2Rl1Sxc8YAV6uy5aI9HQVQhPjG1Vf72Vj/e2iqNZTEFKGUGgoCA3EGXQ1QeTSh4D+I1 z8tQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1706556936; x=1707161736; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=/rTTdTkZrF1wexi3aiNZ7/0XWdKeqDeZCcom0yepX1o=; b=G1S6moeI8rwJSyAX7qsO0xE3Lu5tPtbjCVEOdkqDirfyXHfCB0cJcaTRDYPXDfwnqI 26e54iI/yg6JNOkpw+Ablg1wPcO6ACvXCfIFSQbbdeGPzDdV1F+KoEpLd5e9P30U+ywb Nmww2tk7affDBF3T68Mdqe/dog/SkO0fIUy6hVnxWU2oM6xvQhAYm1F0jB3t+7Jc7mSc OINeBaxYxitpuI3smXyiS286UxwBgDG41CG4elxSzce3QJ8PmYoDso1+GjB1XEOQufwq +YXH5ZMmX0YqhqRsRrkoMJYl5kywNlLncH4O1lAfADYdNp/YSQSRb3SBJesa7VVoo14b GAUw== X-Gm-Message-State: AOJu0YxqRIc8sxIbgezFVuycQF9H3ADcVoZ9UVwkAi2KdChQ1uGHU9/K fvvJQ3XljK7AMK0s4xNdlMvtUM5fy6CaafHyHPuPzviQg+b7ZgbpKapyq9M9+KVJQYDYBc4WIBD S5Q5wT7C4xtKKzAfluqJbJQ== X-Received: from lg.mtv.corp.google.com ([2620:15c:211:202:9b1d:f1ee:f750:93f1]) (user=lokeshgidra job=sendgmr) by 2002:a05:6902:250b:b0:dbe:d0a9:2be3 with SMTP id dt11-20020a056902250b00b00dbed0a92be3mr2244340ybb.3.1706556936414; Mon, 29 Jan 2024 11:35:36 -0800 (PST) Date: Mon, 29 Jan 2024 11:35:12 -0800 In-Reply-To: <20240129193512.123145-1-lokeshgidra@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20240129193512.123145-1-lokeshgidra@google.com> X-Mailer: git-send-email 2.43.0.429.g432eaa2c6b-goog Message-ID: <20240129193512.123145-4-lokeshgidra@google.com> Subject: [PATCH v2 3/3] userfaultfd: use per-vma locks in userfaultfd operations From: Lokesh Gidra To: akpm@linux-foundation.org Cc: lokeshgidra@google.com, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, selinux@vger.kernel.org, surenb@google.com, kernel-team@android.com, aarcange@redhat.com, peterx@redhat.com, david@redhat.com, axelrasmussen@google.com, bgeffon@google.com, willy@infradead.org, jannh@google.com, kaleshsingh@google.com, ngeoffray@google.com, timmurray@google.com, rppt@kernel.org X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: 1789455112284118517 X-GMAIL-MSGID: 1789455112284118517 All userfaultfd operations, except write-protect, opportunistically use per-vma locks to lock vmas. If we fail then fall back to locking mmap-lock in read-mode. Write-protect operation requires mmap_lock as it iterates over multiple vmas. Signed-off-by: Lokesh Gidra --- fs/userfaultfd.c | 13 +-- include/linux/userfaultfd_k.h | 5 +- mm/userfaultfd.c | 175 +++++++++++++++++++++++----------- 3 files changed, 122 insertions(+), 71 deletions(-) diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c index c00a021bcce4..60dcfafdc11a 100644 --- a/fs/userfaultfd.c +++ b/fs/userfaultfd.c @@ -2005,17 +2005,8 @@ static int userfaultfd_move(struct userfaultfd_ctx *ctx, return -EINVAL; if (mmget_not_zero(mm)) { - mmap_read_lock(mm); - - /* Re-check after taking map_changing_lock */ - down_read(&ctx->map_changing_lock); - if (likely(!atomic_read(&ctx->mmap_changing))) - ret = move_pages(ctx, mm, uffdio_move.dst, uffdio_move.src, - uffdio_move.len, uffdio_move.mode); - else - ret = -EAGAIN; - up_read(&ctx->map_changing_lock); - mmap_read_unlock(mm); + ret = move_pages(ctx, uffdio_move.dst, uffdio_move.src, + uffdio_move.len, uffdio_move.mode); mmput(mm); } else { return -ESRCH; diff --git a/include/linux/userfaultfd_k.h b/include/linux/userfaultfd_k.h index 3210c3552976..05d59f74fc88 100644 --- a/include/linux/userfaultfd_k.h +++ b/include/linux/userfaultfd_k.h @@ -138,9 +138,8 @@ extern long uffd_wp_range(struct vm_area_struct *vma, /* move_pages */ void double_pt_lock(spinlock_t *ptl1, spinlock_t *ptl2); void double_pt_unlock(spinlock_t *ptl1, spinlock_t *ptl2); -ssize_t move_pages(struct userfaultfd_ctx *ctx, struct mm_struct *mm, - unsigned long dst_start, unsigned long src_start, - unsigned long len, __u64 flags); +ssize_t move_pages(struct userfaultfd_ctx *ctx, unsigned long dst_start, + unsigned long src_start, unsigned long len, __u64 flags); int move_pages_huge_pmd(struct mm_struct *mm, pmd_t *dst_pmd, pmd_t *src_pmd, pmd_t dst_pmdval, struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma, diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c index 6e2ca04ab04d..d55bf18b80db 100644 --- a/mm/userfaultfd.c +++ b/mm/userfaultfd.c @@ -19,20 +19,39 @@ #include #include "internal.h" -static __always_inline -struct vm_area_struct *find_dst_vma(struct mm_struct *dst_mm, - unsigned long dst_start, - unsigned long len) +void unpin_vma(struct mm_struct *mm, struct vm_area_struct *vma, bool *mmap_locked) +{ + BUG_ON(!vma && !*mmap_locked); + + if (*mmap_locked) { + mmap_read_unlock(mm); + *mmap_locked = false; + } else + vma_end_read(vma); +} + +/* + * Search for VMA and make sure it is stable either by locking it or taking + * mmap_lock. + */ +struct vm_area_struct *find_and_pin_dst_vma(struct mm_struct *dst_mm, + unsigned long dst_start, + unsigned long len, + bool *mmap_locked) { + struct vm_area_struct *dst_vma = lock_vma_under_rcu(dst_mm, dst_start); + if (!dst_vma) { + mmap_read_lock(dst_mm); + *mmap_locked = true; + dst_vma = find_vma(dst_mm, dst_start); + } + /* * Make sure that the dst range is both valid and fully within a * single existing vma. */ - struct vm_area_struct *dst_vma; - - dst_vma = find_vma(dst_mm, dst_start); if (!range_in_vma(dst_vma, dst_start, dst_start + len)) - return NULL; + goto unpin; /* * Check the vma is registered in uffd, this is required to @@ -40,9 +59,13 @@ struct vm_area_struct *find_dst_vma(struct mm_struct *dst_mm, * time. */ if (!dst_vma->vm_userfaultfd_ctx.ctx) - return NULL; + goto unpin; return dst_vma; + +unpin: + unpin_vma(dst_mm, dst_vma, mmap_locked); + return NULL; } /* Check if dst_addr is outside of file's size. Must be called with ptl held. */ @@ -350,7 +373,8 @@ static pmd_t *mm_alloc_pmd(struct mm_struct *mm, unsigned long address) #ifdef CONFIG_HUGETLB_PAGE /* * mfill_atomic processing for HUGETLB vmas. Note that this routine is - * called with mmap_lock held, it will release mmap_lock before returning. + * called with either vma-lock or mmap_lock held, it will release the lock + * before returning. */ static __always_inline ssize_t mfill_atomic_hugetlb( struct userfaultfd_ctx *ctx, @@ -358,7 +382,8 @@ static __always_inline ssize_t mfill_atomic_hugetlb( unsigned long dst_start, unsigned long src_start, unsigned long len, - uffd_flags_t flags) + uffd_flags_t flags, + bool *mmap_locked) { struct mm_struct *dst_mm = dst_vma->vm_mm; int vm_shared = dst_vma->vm_flags & VM_SHARED; @@ -380,7 +405,7 @@ static __always_inline ssize_t mfill_atomic_hugetlb( */ if (uffd_flags_mode_is(flags, MFILL_ATOMIC_ZEROPAGE)) { up_read(&ctx->map_changing_lock); - mmap_read_unlock(dst_mm); + unpin_vma(dst_mm, dst_vma, mmap_locked); return -EINVAL; } @@ -404,12 +429,25 @@ static __always_inline ssize_t mfill_atomic_hugetlb( */ if (!dst_vma) { err = -ENOENT; - dst_vma = find_dst_vma(dst_mm, dst_start, len); - if (!dst_vma || !is_vm_hugetlb_page(dst_vma)) - goto out_unlock; + dst_vma = find_and_pin_dst_vma(dst_mm, dst_start, + len, mmap_locked); + if (!dst_vma) + goto out; + if (!is_vm_hugetlb_page(dst_vma)) + goto out_unlock_vma; err = -EINVAL; if (vma_hpagesize != vma_kernel_pagesize(dst_vma)) + goto out_unlock_vma; + + /* + * If memory mappings are changing because of non-cooperative + * operation (e.g. mremap) running in parallel, bail out and + * request the user to retry later + */ + down_read(&ctx->map_changing_lock); + err = -EAGAIN; + if (atomic_read(&ctx->mmap_changing)) goto out_unlock; vm_shared = dst_vma->vm_flags & VM_SHARED; @@ -465,7 +503,7 @@ static __always_inline ssize_t mfill_atomic_hugetlb( if (unlikely(err == -ENOENT)) { up_read(&ctx->map_changing_lock); - mmap_read_unlock(dst_mm); + unpin_vma(dst_mm, dst_vma, mmap_locked); BUG_ON(!folio); err = copy_folio_from_user(folio, @@ -474,17 +512,6 @@ static __always_inline ssize_t mfill_atomic_hugetlb( err = -EFAULT; goto out; } - mmap_read_lock(dst_mm); - down_read(&ctx->map_changing_lock); - /* - * If memory mappings are changing because of non-cooperative - * operation (e.g. mremap) running in parallel, bail out and - * request the user to retry later - */ - if (atomic_read(ctx->mmap_changing)) { - err = -EAGAIN; - break; - } dst_vma = NULL; goto retry; @@ -505,7 +532,8 @@ static __always_inline ssize_t mfill_atomic_hugetlb( out_unlock: up_read(&ctx->map_changing_lock); - mmap_read_unlock(dst_mm); +out_unlock_vma: + unpin_vma(dst_mm, dst_vma, mmap_locked); out: if (folio) folio_put(folio); @@ -521,7 +549,8 @@ extern ssize_t mfill_atomic_hugetlb(struct userfaultfd_ctx *ctx, unsigned long dst_start, unsigned long src_start, unsigned long len, - uffd_flags_t flags); + uffd_flags_t flags, + bool *mmap_locked); #endif /* CONFIG_HUGETLB_PAGE */ static __always_inline ssize_t mfill_atomic_pte(pmd_t *dst_pmd, @@ -581,6 +610,7 @@ static __always_inline ssize_t mfill_atomic(struct userfaultfd_ctx *ctx, unsigned long src_addr, dst_addr; long copied; struct folio *folio; + bool mmap_locked = false; /* * Sanitize the command parameters: @@ -597,7 +627,14 @@ static __always_inline ssize_t mfill_atomic(struct userfaultfd_ctx *ctx, copied = 0; folio = NULL; retry: - mmap_read_lock(dst_mm); + /* + * Make sure the vma is not shared, that the dst range is + * both valid and fully within a single existing vma. + */ + err = -ENOENT; + dst_vma = find_and_pin_dst_vma(dst_mm, dst_start, len, &mmap_locked); + if (!dst_vma) + goto out; /* * If memory mappings are changing because of non-cooperative @@ -609,15 +646,6 @@ static __always_inline ssize_t mfill_atomic(struct userfaultfd_ctx *ctx, if (atomic_read(&ctx->mmap_changing)) goto out_unlock; - /* - * Make sure the vma is not shared, that the dst range is - * both valid and fully within a single existing vma. - */ - err = -ENOENT; - dst_vma = find_dst_vma(dst_mm, dst_start, len); - if (!dst_vma) - goto out_unlock; - err = -EINVAL; /* * shmem_zero_setup is invoked in mmap for MAP_ANONYMOUS|MAP_SHARED but @@ -638,8 +666,8 @@ static __always_inline ssize_t mfill_atomic(struct userfaultfd_ctx *ctx, * If this is a HUGETLB vma, pass off to appropriate routine */ if (is_vm_hugetlb_page(dst_vma)) - return mfill_atomic_hugetlb(ctx, dst_vma, dst_start, - src_start, len, flags); + return mfill_atomic_hugetlb(ctx, dst_vma, dst_start, src_start + len, flags, &mmap_locked); if (!vma_is_anonymous(dst_vma) && !vma_is_shmem(dst_vma)) goto out_unlock; @@ -699,7 +727,8 @@ static __always_inline ssize_t mfill_atomic(struct userfaultfd_ctx *ctx, void *kaddr; up_read(&ctx->map_changing_lock); - mmap_read_unlock(dst_mm); + unpin_vma(dst_mm, dst_vma, &mmap_locked); + BUG_ON(!folio); kaddr = kmap_local_folio(folio, 0); @@ -730,7 +759,7 @@ static __always_inline ssize_t mfill_atomic(struct userfaultfd_ctx *ctx, out_unlock: up_read(&ctx->map_changing_lock); - mmap_read_unlock(dst_mm); + unpin_vma(dst_mm, dst_vma, &mmap_locked); out: if (folio) folio_put(folio); @@ -1285,8 +1314,6 @@ static int validate_move_areas(struct userfaultfd_ctx *ctx, * @len: length of the virtual memory range * @mode: flags from uffdio_move.mode * - * Must be called with mmap_lock held for read. - * * move_pages() remaps arbitrary anonymous pages atomically in zero * copy. It only works on non shared anonymous pages because those can * be relocated without generating non linear anon_vmas in the rmap @@ -1353,15 +1380,16 @@ static int validate_move_areas(struct userfaultfd_ctx *ctx, * could be obtained. This is the only additional complexity added to * the rmap code to provide this anonymous page remapping functionality. */ -ssize_t move_pages(struct userfaultfd_ctx *ctx, struct mm_struct *mm, - unsigned long dst_start, unsigned long src_start, - unsigned long len, __u64 mode) +ssize_t move_pages(struct userfaultfd_ctx *ctx, unsigned long dst_start, + unsigned long src_start, unsigned long len, __u64 mode) { + struct mm_struct *mm = ctx->mm; struct vm_area_struct *src_vma, *dst_vma; unsigned long src_addr, dst_addr; pmd_t *src_pmd, *dst_pmd; long err = -EINVAL; ssize_t moved = 0; + bool mmap_locked = false; /* Sanitize the command parameters. */ if (WARN_ON_ONCE(src_start & ~PAGE_MASK) || @@ -1374,28 +1402,52 @@ ssize_t move_pages(struct userfaultfd_ctx *ctx, struct mm_struct *mm, WARN_ON_ONCE(dst_start + len <= dst_start)) goto out; + dst_vma = NULL; + src_vma = lock_vma_under_rcu(mm, src_start); + if (src_vma) { + dst_vma = lock_vma_under_rcu(mm, dst_start); + if (!dst_vma) + vma_end_read(src_vma); + } + + /* If we failed to lock both VMAs, fall back to mmap_lock */ + if (!dst_vma) { + mmap_read_lock(mm); + mmap_locked = true; + src_vma = find_vma(mm, src_start); + if (!src_vma) + goto out_unlock_mmap; + dst_vma = find_vma(mm, dst_start); + if (!dst_vma) + goto out_unlock_mmap; + } + + /* Re-check after taking map_changing_lock */ + down_read(&ctx->map_changing_lock); + if (likely(atomic_read(&ctx->mmap_changing))) { + err = -EAGAIN; + goto out_unlock; + } /* * Make sure the vma is not shared, that the src and dst remap * ranges are both valid and fully within a single existing * vma. */ - src_vma = find_vma(mm, src_start); - if (!src_vma || (src_vma->vm_flags & VM_SHARED)) - goto out; + if (src_vma->vm_flags & VM_SHARED) + goto out_unlock; if (src_start < src_vma->vm_start || src_start + len > src_vma->vm_end) - goto out; + goto out_unlock; - dst_vma = find_vma(mm, dst_start); - if (!dst_vma || (dst_vma->vm_flags & VM_SHARED)) - goto out; + if (dst_vma->vm_flags & VM_SHARED) + goto out_unlock; if (dst_start < dst_vma->vm_start || dst_start + len > dst_vma->vm_end) - goto out; + goto out_unlock; err = validate_move_areas(ctx, src_vma, dst_vma); if (err) - goto out; + goto out_unlock; for (src_addr = src_start, dst_addr = dst_start; src_addr < src_start + len;) { @@ -1512,6 +1564,15 @@ ssize_t move_pages(struct userfaultfd_ctx *ctx, struct mm_struct *mm, moved += step_size; } +out_unlock: + up_read(&ctx->map_changing_lock); +out_unlock_mmap: + if (mmap_locked) + mmap_read_unlock(mm); + else { + vma_end_read(dst_vma); + vma_end_read(src_vma); + } out: VM_WARN_ON(moved < 0); VM_WARN_ON(err > 0);