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AJvYcCXwz9FyKtPJTeP+44SWY7d1XD8yG4XEhW4Gt5fN1GQDqizyOVoPzqZxFidRX1GuC1eW4MpefDsz5m+HT/hEDJvU9Fg= X-Gm-Message-State: AOJu0YxYsLybjHerKefQjwDxQ6hlNOXvONiHcZbBhSXcMfFZo0Ysk7fo IrtdgCNUu7+MiM+PyP9ZJ+iF8AJmzkXFwnqRF1ZL5eiGpcuLs7DOVL/YunN+4F+vBy5ICdTUh9H dvpfqyTMJy0jwgZeLAM/xKg== X-Google-Smtp-Source: AGHT+IHHi2mCkEldISrNhtoRZCLnocCFS9qBcw8e+39nrcye3IQvcjCcfdDQNRvMWp/R1wX/qkVergX2FymdVGvJXg== X-Received: from lg.mtv.corp.google.com ([2620:15c:211:202:6186:87a3:6b94:9b81]) (user=lokeshgidra job=sendgmr) by 2002:a05:6902:f11:b0:dc6:db9b:7a6d with SMTP id et17-20020a0569020f1100b00dc6db9b7a6dmr83663ybb.13.1708021690138; Thu, 15 Feb 2024 10:28:10 -0800 (PST) Date: Thu, 15 Feb 2024 10:27:53 -0800 In-Reply-To: <20240215182756.3448972-1-lokeshgidra@google.com> Mime-Version: 1.0 References: <20240215182756.3448972-1-lokeshgidra@google.com> X-Mailer: git-send-email 2.43.0.687.g38aa6559b0-goog Message-ID: <20240215182756.3448972-2-lokeshgidra@google.com> Subject: [PATCH v7 1/4] userfaultfd: move userfaultfd_ctx struct to header file 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, Liam.Howlett@oracle.com, ryan.roberts@arm.com X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: EB769140026 X-Stat-Signature: 464jnmppji7gxkkmnhtcd1dgkgxposzj X-Rspam-User: X-HE-Tag: 1708021690-662598 X-HE-Meta: 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 7GFfK+NH 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 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: Moving the struct to userfaultfd_k.h to be accessible from mm/userfaultfd.c. There are no other changes in the struct. This is required to prepare for using per-vma locks in userfaultfd operations. Signed-off-by: Lokesh Gidra Reviewed-by: Mike Rapoport (IBM) Reviewed-by: Liam R. Howlett --- fs/userfaultfd.c | 39 ----------------------------------- include/linux/userfaultfd_k.h | 39 +++++++++++++++++++++++++++++++++++ 2 files changed, 39 insertions(+), 39 deletions(-) diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c index 05c8e8a05427..58331b83d648 100644 --- a/fs/userfaultfd.c +++ b/fs/userfaultfd.c @@ -50,45 +50,6 @@ static struct ctl_table vm_userfaultfd_table[] = { static struct kmem_cache *userfaultfd_ctx_cachep __ro_after_init; -/* - * Start with fault_pending_wqh and fault_wqh so they're more likely - * to be in the same cacheline. - * - * Locking order: - * fd_wqh.lock - * fault_pending_wqh.lock - * fault_wqh.lock - * event_wqh.lock - * - * To avoid deadlocks, IRQs must be disabled when taking any of the above locks, - * since fd_wqh.lock is taken by aio_poll() while it's holding a lock that's - * also taken in IRQ context. - */ -struct userfaultfd_ctx { - /* waitqueue head for the pending (i.e. not read) userfaults */ - wait_queue_head_t fault_pending_wqh; - /* waitqueue head for the userfaults */ - wait_queue_head_t fault_wqh; - /* waitqueue head for the pseudo fd to wakeup poll/read */ - wait_queue_head_t fd_wqh; - /* waitqueue head for events */ - wait_queue_head_t event_wqh; - /* a refile sequence protected by fault_pending_wqh lock */ - seqcount_spinlock_t refile_seq; - /* pseudo fd refcounting */ - refcount_t refcount; - /* userfaultfd syscall flags */ - unsigned int flags; - /* features requested from the userspace */ - unsigned int features; - /* released */ - bool released; - /* memory mappings are changing because of non-cooperative event */ - atomic_t mmap_changing; - /* mm with one ore more vmas attached to this userfaultfd_ctx */ - struct mm_struct *mm; -}; - struct userfaultfd_fork_ctx { struct userfaultfd_ctx *orig; struct userfaultfd_ctx *new; diff --git a/include/linux/userfaultfd_k.h b/include/linux/userfaultfd_k.h index e4056547fbe6..691d928ee864 100644 --- a/include/linux/userfaultfd_k.h +++ b/include/linux/userfaultfd_k.h @@ -36,6 +36,45 @@ #define UFFD_SHARED_FCNTL_FLAGS (O_CLOEXEC | O_NONBLOCK) #define UFFD_FLAGS_SET (EFD_SHARED_FCNTL_FLAGS) +/* + * Start with fault_pending_wqh and fault_wqh so they're more likely + * to be in the same cacheline. + * + * Locking order: + * fd_wqh.lock + * fault_pending_wqh.lock + * fault_wqh.lock + * event_wqh.lock + * + * To avoid deadlocks, IRQs must be disabled when taking any of the above locks, + * since fd_wqh.lock is taken by aio_poll() while it's holding a lock that's + * also taken in IRQ context. + */ +struct userfaultfd_ctx { + /* waitqueue head for the pending (i.e. not read) userfaults */ + wait_queue_head_t fault_pending_wqh; + /* waitqueue head for the userfaults */ + wait_queue_head_t fault_wqh; + /* waitqueue head for the pseudo fd to wakeup poll/read */ + wait_queue_head_t fd_wqh; + /* waitqueue head for events */ + wait_queue_head_t event_wqh; + /* a refile sequence protected by fault_pending_wqh lock */ + seqcount_spinlock_t refile_seq; + /* pseudo fd refcounting */ + refcount_t refcount; + /* userfaultfd syscall flags */ + unsigned int flags; + /* features requested from the userspace */ + unsigned int features; + /* released */ + bool released; + /* memory mappings are changing because of non-cooperative event */ + atomic_t mmap_changing; + /* mm with one ore more vmas attached to this userfaultfd_ctx */ + struct mm_struct *mm; +}; + extern vm_fault_t handle_userfault(struct vm_fault *vmf, unsigned long reason); /* A combined operation mode + behavior flags. */ From patchwork Thu Feb 15 18:27:54 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Lokesh Gidra X-Patchwork-Id: 13559023 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]) by smtp.lore.kernel.org (Postfix) with ESMTP id E9DF6C48BEF for ; 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This ensures that if userspace requests event notification for non-cooperative operations (e.g. mremap), userfaultfd operations don't occur concurrently. This can be achieved by using a separate read-write semaphore in userfaultfd_ctx such that increments are done in write-mode and loads in read-mode, thereby eliminating the dependency on mmap_lock for this purpose. This is a preparatory step before we replace mmap_lock usage with per-vma locks in fill/move ioctls. Signed-off-by: Lokesh Gidra Reviewed-by: Mike Rapoport (IBM) Reviewed-by: Liam R. Howlett --- fs/userfaultfd.c | 40 ++++++++++++---------- include/linux/userfaultfd_k.h | 31 ++++++++++-------- mm/userfaultfd.c | 62 ++++++++++++++++++++--------------- 3 files changed, 75 insertions(+), 58 deletions(-) diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c index 58331b83d648..c00a021bcce4 100644 --- a/fs/userfaultfd.c +++ b/fs/userfaultfd.c @@ -685,12 +685,15 @@ int dup_userfaultfd(struct vm_area_struct *vma, struct list_head *fcs) ctx->flags = octx->flags; ctx->features = octx->features; ctx->released = false; + init_rwsem(&ctx->map_changing_lock); atomic_set(&ctx->mmap_changing, 0); ctx->mm = vma->vm_mm; mmgrab(ctx->mm); userfaultfd_ctx_get(octx); + down_write(&octx->map_changing_lock); atomic_inc(&octx->mmap_changing); + up_write(&octx->map_changing_lock); fctx->orig = octx; fctx->new = ctx; list_add_tail(&fctx->list, fcs); @@ -737,7 +740,9 @@ void mremap_userfaultfd_prep(struct vm_area_struct *vma, if (ctx->features & UFFD_FEATURE_EVENT_REMAP) { vm_ctx->ctx = ctx; userfaultfd_ctx_get(ctx); + down_write(&ctx->map_changing_lock); atomic_inc(&ctx->mmap_changing); + up_write(&ctx->map_changing_lock); } else { /* Drop uffd context if remap feature not enabled */ vma_start_write(vma); @@ -783,7 +788,9 @@ bool userfaultfd_remove(struct vm_area_struct *vma, return true; userfaultfd_ctx_get(ctx); + down_write(&ctx->map_changing_lock); atomic_inc(&ctx->mmap_changing); + up_write(&ctx->map_changing_lock); mmap_read_unlock(mm); msg_init(&ewq.msg); @@ -825,7 +832,9 @@ int userfaultfd_unmap_prep(struct vm_area_struct *vma, unsigned long start, return -ENOMEM; userfaultfd_ctx_get(ctx); + down_write(&ctx->map_changing_lock); atomic_inc(&ctx->mmap_changing); + up_write(&ctx->map_changing_lock); unmap_ctx->ctx = ctx; unmap_ctx->start = start; unmap_ctx->end = end; @@ -1709,9 +1718,8 @@ static int userfaultfd_copy(struct userfaultfd_ctx *ctx, if (uffdio_copy.mode & UFFDIO_COPY_MODE_WP) flags |= MFILL_ATOMIC_WP; if (mmget_not_zero(ctx->mm)) { - ret = mfill_atomic_copy(ctx->mm, uffdio_copy.dst, uffdio_copy.src, - uffdio_copy.len, &ctx->mmap_changing, - flags); + ret = mfill_atomic_copy(ctx, uffdio_copy.dst, uffdio_copy.src, + uffdio_copy.len, flags); mmput(ctx->mm); } else { return -ESRCH; @@ -1761,9 +1769,8 @@ static int userfaultfd_zeropage(struct userfaultfd_ctx *ctx, goto out; if (mmget_not_zero(ctx->mm)) { - ret = mfill_atomic_zeropage(ctx->mm, uffdio_zeropage.range.start, - uffdio_zeropage.range.len, - &ctx->mmap_changing); + ret = mfill_atomic_zeropage(ctx, uffdio_zeropage.range.start, + uffdio_zeropage.range.len); mmput(ctx->mm); } else { return -ESRCH; @@ -1818,9 +1825,8 @@ static int userfaultfd_writeprotect(struct userfaultfd_ctx *ctx, return -EINVAL; if (mmget_not_zero(ctx->mm)) { - ret = mwriteprotect_range(ctx->mm, uffdio_wp.range.start, - uffdio_wp.range.len, mode_wp, - &ctx->mmap_changing); + ret = mwriteprotect_range(ctx, uffdio_wp.range.start, + uffdio_wp.range.len, mode_wp); mmput(ctx->mm); } else { return -ESRCH; @@ -1870,9 +1876,8 @@ static int userfaultfd_continue(struct userfaultfd_ctx *ctx, unsigned long arg) flags |= MFILL_ATOMIC_WP; if (mmget_not_zero(ctx->mm)) { - ret = mfill_atomic_continue(ctx->mm, uffdio_continue.range.start, - uffdio_continue.range.len, - &ctx->mmap_changing, flags); + ret = mfill_atomic_continue(ctx, uffdio_continue.range.start, + uffdio_continue.range.len, flags); mmput(ctx->mm); } else { return -ESRCH; @@ -1925,9 +1930,8 @@ static inline int userfaultfd_poison(struct userfaultfd_ctx *ctx, unsigned long goto out; if (mmget_not_zero(ctx->mm)) { - ret = mfill_atomic_poison(ctx->mm, uffdio_poison.range.start, - uffdio_poison.range.len, - &ctx->mmap_changing, 0); + ret = mfill_atomic_poison(ctx, uffdio_poison.range.start, + uffdio_poison.range.len, 0); mmput(ctx->mm); } else { return -ESRCH; @@ -2003,13 +2007,14 @@ static int userfaultfd_move(struct userfaultfd_ctx *ctx, if (mmget_not_zero(mm)) { mmap_read_lock(mm); - /* Re-check after taking mmap_lock */ + /* 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); mmput(mm); } else { @@ -2216,6 +2221,7 @@ static int new_userfaultfd(int flags) ctx->flags = flags; ctx->features = 0; ctx->released = false; + init_rwsem(&ctx->map_changing_lock); atomic_set(&ctx->mmap_changing, 0); ctx->mm = current->mm; /* prevent the mm struct to be freed */ diff --git a/include/linux/userfaultfd_k.h b/include/linux/userfaultfd_k.h index 691d928ee864..3210c3552976 100644 --- a/include/linux/userfaultfd_k.h +++ b/include/linux/userfaultfd_k.h @@ -69,6 +69,13 @@ struct userfaultfd_ctx { unsigned int features; /* released */ bool released; + /* + * Prevents userfaultfd operations (fill/move/wp) from happening while + * some non-cooperative event(s) is taking place. Increments are done + * in write-mode. Whereas, userfaultfd operations, which includes + * reading mmap_changing, is done under read-mode. + */ + struct rw_semaphore map_changing_lock; /* memory mappings are changing because of non-cooperative event */ atomic_t mmap_changing; /* mm with one ore more vmas attached to this userfaultfd_ctx */ @@ -113,22 +120,18 @@ extern int mfill_atomic_install_pte(pmd_t *dst_pmd, unsigned long dst_addr, struct page *page, bool newly_allocated, uffd_flags_t flags); -extern ssize_t mfill_atomic_copy(struct mm_struct *dst_mm, unsigned long dst_start, +extern ssize_t mfill_atomic_copy(struct userfaultfd_ctx *ctx, unsigned long dst_start, unsigned long src_start, unsigned long len, - atomic_t *mmap_changing, uffd_flags_t flags); -extern ssize_t mfill_atomic_zeropage(struct mm_struct *dst_mm, + uffd_flags_t flags); +extern ssize_t mfill_atomic_zeropage(struct userfaultfd_ctx *ctx, unsigned long dst_start, - unsigned long len, - atomic_t *mmap_changing); -extern ssize_t mfill_atomic_continue(struct mm_struct *dst_mm, unsigned long dst_start, - unsigned long len, atomic_t *mmap_changing, - uffd_flags_t flags); -extern ssize_t mfill_atomic_poison(struct mm_struct *dst_mm, unsigned long start, - unsigned long len, atomic_t *mmap_changing, - uffd_flags_t flags); -extern int mwriteprotect_range(struct mm_struct *dst_mm, - unsigned long start, unsigned long len, - bool enable_wp, atomic_t *mmap_changing); + unsigned long len); +extern ssize_t mfill_atomic_continue(struct userfaultfd_ctx *ctx, unsigned long dst_start, + unsigned long len, uffd_flags_t flags); +extern ssize_t mfill_atomic_poison(struct userfaultfd_ctx *ctx, unsigned long start, + unsigned long len, uffd_flags_t flags); +extern int mwriteprotect_range(struct userfaultfd_ctx *ctx, unsigned long start, + unsigned long len, bool enable_wp); extern long uffd_wp_range(struct vm_area_struct *vma, unsigned long start, unsigned long len, bool enable_wp); diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c index 9cc93cc1330b..74aad0831e40 100644 --- a/mm/userfaultfd.c +++ b/mm/userfaultfd.c @@ -353,11 +353,11 @@ static pmd_t *mm_alloc_pmd(struct mm_struct *mm, unsigned long address) * called with mmap_lock held, it will release mmap_lock before returning. */ static __always_inline ssize_t mfill_atomic_hugetlb( + struct userfaultfd_ctx *ctx, struct vm_area_struct *dst_vma, unsigned long dst_start, unsigned long src_start, unsigned long len, - atomic_t *mmap_changing, uffd_flags_t flags) { struct mm_struct *dst_mm = dst_vma->vm_mm; @@ -379,6 +379,7 @@ static __always_inline ssize_t mfill_atomic_hugetlb( * feature is not supported. */ if (uffd_flags_mode_is(flags, MFILL_ATOMIC_ZEROPAGE)) { + up_read(&ctx->map_changing_lock); mmap_read_unlock(dst_mm); return -EINVAL; } @@ -463,6 +464,7 @@ static __always_inline ssize_t mfill_atomic_hugetlb( cond_resched(); if (unlikely(err == -ENOENT)) { + up_read(&ctx->map_changing_lock); mmap_read_unlock(dst_mm); BUG_ON(!folio); @@ -473,12 +475,13 @@ static __always_inline ssize_t mfill_atomic_hugetlb( 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 (mmap_changing && atomic_read(mmap_changing)) { + if (atomic_read(&ctx->mmap_changing)) { err = -EAGAIN; break; } @@ -501,6 +504,7 @@ static __always_inline ssize_t mfill_atomic_hugetlb( } out_unlock: + up_read(&ctx->map_changing_lock); mmap_read_unlock(dst_mm); out: if (folio) @@ -512,11 +516,11 @@ static __always_inline ssize_t mfill_atomic_hugetlb( } #else /* !CONFIG_HUGETLB_PAGE */ /* fail at build time if gcc attempts to use this */ -extern ssize_t mfill_atomic_hugetlb(struct vm_area_struct *dst_vma, +extern ssize_t mfill_atomic_hugetlb(struct userfaultfd_ctx *ctx, + struct vm_area_struct *dst_vma, unsigned long dst_start, unsigned long src_start, unsigned long len, - atomic_t *mmap_changing, uffd_flags_t flags); #endif /* CONFIG_HUGETLB_PAGE */ @@ -564,13 +568,13 @@ static __always_inline ssize_t mfill_atomic_pte(pmd_t *dst_pmd, return err; } -static __always_inline ssize_t mfill_atomic(struct mm_struct *dst_mm, +static __always_inline ssize_t mfill_atomic(struct userfaultfd_ctx *ctx, unsigned long dst_start, unsigned long src_start, unsigned long len, - atomic_t *mmap_changing, uffd_flags_t flags) { + struct mm_struct *dst_mm = ctx->mm; struct vm_area_struct *dst_vma; ssize_t err; pmd_t *dst_pmd; @@ -600,8 +604,9 @@ static __always_inline ssize_t mfill_atomic(struct mm_struct *dst_mm, * 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 (mmap_changing && atomic_read(mmap_changing)) + if (atomic_read(&ctx->mmap_changing)) goto out_unlock; /* @@ -633,8 +638,8 @@ static __always_inline ssize_t mfill_atomic(struct mm_struct *dst_mm, * If this is a HUGETLB vma, pass off to appropriate routine */ if (is_vm_hugetlb_page(dst_vma)) - return mfill_atomic_hugetlb(dst_vma, dst_start, src_start, - len, mmap_changing, flags); + 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; @@ -693,6 +698,7 @@ static __always_inline ssize_t mfill_atomic(struct mm_struct *dst_mm, if (unlikely(err == -ENOENT)) { void *kaddr; + up_read(&ctx->map_changing_lock); mmap_read_unlock(dst_mm); BUG_ON(!folio); @@ -723,6 +729,7 @@ static __always_inline ssize_t mfill_atomic(struct mm_struct *dst_mm, } out_unlock: + up_read(&ctx->map_changing_lock); mmap_read_unlock(dst_mm); out: if (folio) @@ -733,34 +740,33 @@ static __always_inline ssize_t mfill_atomic(struct mm_struct *dst_mm, return copied ? copied : err; } -ssize_t mfill_atomic_copy(struct mm_struct *dst_mm, unsigned long dst_start, +ssize_t mfill_atomic_copy(struct userfaultfd_ctx *ctx, unsigned long dst_start, unsigned long src_start, unsigned long len, - atomic_t *mmap_changing, uffd_flags_t flags) + uffd_flags_t flags) { - return mfill_atomic(dst_mm, dst_start, src_start, len, mmap_changing, + return mfill_atomic(ctx, dst_start, src_start, len, uffd_flags_set_mode(flags, MFILL_ATOMIC_COPY)); } -ssize_t mfill_atomic_zeropage(struct mm_struct *dst_mm, unsigned long start, - unsigned long len, atomic_t *mmap_changing) +ssize_t mfill_atomic_zeropage(struct userfaultfd_ctx *ctx, + unsigned long start, + unsigned long len) { - return mfill_atomic(dst_mm, start, 0, len, mmap_changing, + return mfill_atomic(ctx, start, 0, len, uffd_flags_set_mode(0, MFILL_ATOMIC_ZEROPAGE)); } -ssize_t mfill_atomic_continue(struct mm_struct *dst_mm, unsigned long start, - unsigned long len, atomic_t *mmap_changing, - uffd_flags_t flags) +ssize_t mfill_atomic_continue(struct userfaultfd_ctx *ctx, unsigned long start, + unsigned long len, uffd_flags_t flags) { - return mfill_atomic(dst_mm, start, 0, len, mmap_changing, + return mfill_atomic(ctx, start, 0, len, uffd_flags_set_mode(flags, MFILL_ATOMIC_CONTINUE)); } -ssize_t mfill_atomic_poison(struct mm_struct *dst_mm, unsigned long start, - unsigned long len, atomic_t *mmap_changing, - uffd_flags_t flags) +ssize_t mfill_atomic_poison(struct userfaultfd_ctx *ctx, unsigned long start, + unsigned long len, uffd_flags_t flags) { - return mfill_atomic(dst_mm, start, 0, len, mmap_changing, + return mfill_atomic(ctx, start, 0, len, uffd_flags_set_mode(flags, MFILL_ATOMIC_POISON)); } @@ -793,10 +799,10 @@ long uffd_wp_range(struct vm_area_struct *dst_vma, return ret; } -int mwriteprotect_range(struct mm_struct *dst_mm, unsigned long start, - unsigned long len, bool enable_wp, - atomic_t *mmap_changing) +int mwriteprotect_range(struct userfaultfd_ctx *ctx, unsigned long start, + unsigned long len, bool enable_wp) { + struct mm_struct *dst_mm = ctx->mm; unsigned long end = start + len; unsigned long _start, _end; struct vm_area_struct *dst_vma; @@ -820,8 +826,9 @@ int mwriteprotect_range(struct mm_struct *dst_mm, unsigned long start, * 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 (mmap_changing && atomic_read(mmap_changing)) + if (atomic_read(&ctx->mmap_changing)) goto out_unlock; err = -ENOENT; @@ -850,6 +857,7 @@ int mwriteprotect_range(struct mm_struct *dst_mm, unsigned long start, err = 0; } out_unlock: + up_read(&ctx->map_changing_lock); mmap_read_unlock(dst_mm); return err; } From patchwork Thu Feb 15 18:27:55 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Lokesh Gidra X-Patchwork-Id: 13559024 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]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9D08DC48BC4 for ; Thu, 15 Feb 2024 18:28:18 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 7803C8D0010; Thu, 15 Feb 2024 13:28:17 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 708F78D0006; Thu, 15 Feb 2024 13:28:17 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 55C848D0010; 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Thu, 15 Feb 2024 10:28:14 -0800 (PST) Date: Thu, 15 Feb 2024 10:27:55 -0800 In-Reply-To: <20240215182756.3448972-1-lokeshgidra@google.com> Mime-Version: 1.0 References: <20240215182756.3448972-1-lokeshgidra@google.com> X-Mailer: git-send-email 2.43.0.687.g38aa6559b0-goog Message-ID: <20240215182756.3448972-4-lokeshgidra@google.com> Subject: [PATCH v7 3/4] mm: add vma_assert_locked() for !CONFIG_PER_VMA_LOCK 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, Liam.Howlett@oracle.com, ryan.roberts@arm.com X-Rspamd-Queue-Id: 384B38001B X-Rspam-User: X-Rspamd-Server: rspam11 X-Stat-Signature: 7d4eysasxnc13qug1814n8xboapre8wp X-HE-Tag: 1708021695-526655 X-HE-Meta: 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 y3NiT76P 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 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: vma_assert_locked() is needed to replace mmap_assert_locked() once we start using per-vma locks in userfaultfd operations. In !CONFIG_PER_VMA_LOCK case when mm is locked, it implies that the given VMA is locked. Signed-off-by: Lokesh Gidra Reviewed-by: Suren Baghdasaryan --- include/linux/mm.h | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/include/linux/mm.h b/include/linux/mm.h index 3c85634b186c..5ece3ad34ef8 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -781,6 +781,11 @@ static inline struct vm_area_struct *lock_vma_under_rcu(struct mm_struct *mm, return NULL; } +static inline void vma_assert_locked(struct vm_area_struct *vma) +{ + mmap_assert_locked(vma->vm_mm); +} + static inline void release_fault_lock(struct vm_fault *vmf) { mmap_read_unlock(vmf->vma->vm_mm); From patchwork Thu Feb 15 18:27:56 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Lokesh Gidra X-Patchwork-Id: 13559025 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]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4C14BC48BC4 for ; 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AJvYcCUife8aoTqMC4OfaBelzph6jNMlrCl5Ez+oD0dnr4hFVyphMUWgEKAY3CGqfpLrvEC7P8y8rQzuVgTjrefwKiLXBRg= X-Gm-Message-State: AOJu0YzSOgUfMK/rnrDrtVCX/fKDG9ATlh3HZygpi9haBgs3J7d1RnO/ o7uBnYbhW++SnFRS4R9hdeZx7MVNuYlN3k+zXNk1dm8WpQHxaErINRSoJs4ngQ6J1X3kqvZNbah Rdl7kx0Irz2kf7pwZDIBcSw== X-Google-Smtp-Source: AGHT+IHGae+uPzrc4Hv5tlNVkUxfz8K6+IwOsbpum+6krBpkrYXvIIY2FdVy1Ib5pZBj1K2oQGCjrbGbqVY/rhISHw== X-Received: from lg.mtv.corp.google.com ([2620:15c:211:202:6186:87a3:6b94:9b81]) (user=lokeshgidra job=sendgmr) by 2002:a81:4402:0:b0:607:7927:dea1 with SMTP id r2-20020a814402000000b006077927dea1mr1073112ywa.1.1708021696307; Thu, 15 Feb 2024 10:28:16 -0800 (PST) Date: Thu, 15 Feb 2024 10:27:56 -0800 In-Reply-To: <20240215182756.3448972-1-lokeshgidra@google.com> Mime-Version: 1.0 References: <20240215182756.3448972-1-lokeshgidra@google.com> X-Mailer: git-send-email 2.43.0.687.g38aa6559b0-goog Message-ID: <20240215182756.3448972-5-lokeshgidra@google.com> Subject: [PATCH v7 4/4] 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, Liam.Howlett@oracle.com, ryan.roberts@arm.com X-Rspamd-Queue-Id: 2E6AF1C0023 X-Rspam-User: X-Stat-Signature: yznanx3384a9z4dprtzid8x5uz5oumcx X-Rspamd-Server: rspam03 X-HE-Tag: 1708021696-604009 X-HE-Meta: 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 u/87yV0o 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 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: All userfaultfd operations, except write-protect, opportunistically use per-vma locks to lock vmas. On failure, attempt again inside mmap_lock critical section. Write-protect operation requires mmap_lock as it iterates over multiple vmas. Signed-off-by: Lokesh Gidra Reviewed-by: Liam R. Howlett --- fs/userfaultfd.c | 13 +- include/linux/userfaultfd_k.h | 5 +- mm/huge_memory.c | 5 +- mm/userfaultfd.c | 380 ++++++++++++++++++++++++++-------- 4 files changed, 299 insertions(+), 104 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/huge_memory.c b/mm/huge_memory.c index 016e20bd813e..c337ebb4f7ab 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -2158,7 +2158,7 @@ int change_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma, #ifdef CONFIG_USERFAULTFD /* - * The PT lock for src_pmd and the mmap_lock for reading are held by + * The PT lock for src_pmd and dst_vma/src_vma (for reading) are locked by * the caller, but it must return after releasing the page_table_lock. * Just move the page from src_pmd to dst_pmd if possible. * Return zero if succeeded in moving the page, -EAGAIN if it needs to be @@ -2181,7 +2181,8 @@ int move_pages_huge_pmd(struct mm_struct *mm, pmd_t *dst_pmd, pmd_t *src_pmd, pm src_ptl = pmd_lockptr(mm, src_pmd); lockdep_assert_held(src_ptl); - mmap_assert_locked(mm); + vma_assert_locked(src_vma); + vma_assert_locked(dst_vma); /* Sanity checks before the operation */ if (WARN_ON_ONCE(!pmd_none(dst_pmdval)) || WARN_ON_ONCE(src_addr & ~HPAGE_PMD_MASK) || diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c index 74aad0831e40..4744d6a96f96 100644 --- a/mm/userfaultfd.c +++ b/mm/userfaultfd.c @@ -20,19 +20,11 @@ #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) +bool validate_dst_vma(struct vm_area_struct *dst_vma, unsigned long dst_end) { - /* - * 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; + /* Make sure that the dst range is fully within dst_vma. */ + if (dst_end > dst_vma->vm_end) + return false; /* * Check the vma is registered in uffd, this is required to @@ -40,11 +32,122 @@ struct vm_area_struct *find_dst_vma(struct mm_struct *dst_mm, * time. */ if (!dst_vma->vm_userfaultfd_ctx.ctx) - return NULL; + return false; + + return true; +} + +static __always_inline +struct vm_area_struct *find_vma_and_prepare_anon(struct mm_struct *mm, + unsigned long addr) +{ + struct vm_area_struct *vma; + + mmap_assert_locked(mm); + vma = vma_lookup(mm, addr); + if (!vma) + vma = ERR_PTR(-ENOENT); + else if (!(vma->vm_flags & VM_SHARED) && + unlikely(anon_vma_prepare(vma))) + vma = ERR_PTR(-ENOMEM); + + return vma; +} + +#ifdef CONFIG_PER_VMA_LOCK +/* + * lock_vma() - Lookup and lock vma corresponding to @address. + * @mm: mm to search vma in. + * @address: address that the vma should contain. + * + * Should be called without holding mmap_lock. vma should be unlocked after use + * with unlock_vma(). + * + * Return: A locked vma containing @address, -ENOENT if no vma is found, or + * -ENOMEM if anon_vma couldn't be allocated. + */ +static struct vm_area_struct *lock_vma(struct mm_struct *mm, + unsigned long address) +{ + struct vm_area_struct *vma; + + vma = lock_vma_under_rcu(mm, address); + if (vma) { + /* + * lock_vma_under_rcu() only checks anon_vma for private + * anonymous mappings. But we need to ensure it is assigned in + * private file-backed vmas as well. + */ + if (!(vma->vm_flags & VM_SHARED) && unlikely(!vma->anon_vma)) + vma_end_read(vma); + else + return vma; + } + + mmap_read_lock(mm); + vma = find_vma_and_prepare_anon(mm, address); + if (!IS_ERR(vma)) { + /* + * We cannot use vma_start_read() as it may fail due to + * false locked (see comment in vma_start_read()). We + * can avoid that by directly locking vm_lock under + * mmap_lock, which guarantees that nobody can lock the + * vma for write (vma_start_write()) under us. + */ + down_read(&vma->vm_lock->lock); + } + + mmap_read_unlock(mm); + return vma; +} + +static struct vm_area_struct *uffd_mfill_lock(struct mm_struct *dst_mm, + unsigned long dst_start, + unsigned long len) +{ + struct vm_area_struct *dst_vma; + dst_vma = lock_vma(dst_mm, dst_start); + if (IS_ERR(dst_vma) || validate_dst_vma(dst_vma, dst_start + len)) + return dst_vma; + + vma_end_read(dst_vma); + return ERR_PTR(-ENOENT); +} + +static void uffd_mfill_unlock(struct vm_area_struct *vma) +{ + vma_end_read(vma); +} + +#else + +static struct vm_area_struct *uffd_mfill_lock(struct mm_struct *dst_mm, + unsigned long dst_start, + unsigned long len) +{ + struct vm_area_struct *dst_vma; + + mmap_read_lock(dst_mm); + dst_vma = find_vma_and_prepare_anon(dst_mm, dst_start); + if (IS_ERR(dst_vma)) + goto out_unlock; + + if (validate_dst_vma(dst_vma, dst_start + len)) + return dst_vma; + + dst_vma = ERR_PTR(-ENOENT); +out_unlock: + mmap_read_unlock(dst_mm); return dst_vma; } +static void uffd_mfill_unlock(struct vm_area_struct *vma) +{ + mmap_read_unlock(vma->vm_mm); +} +#endif + /* Check if dst_addr is outside of file's size. Must be called with ptl held. */ static bool mfill_file_over_size(struct vm_area_struct *dst_vma, unsigned long dst_addr) @@ -350,7 +453,8 @@ 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, @@ -361,7 +465,6 @@ static __always_inline ssize_t mfill_atomic_hugetlb( uffd_flags_t flags) { struct mm_struct *dst_mm = dst_vma->vm_mm; - int vm_shared = dst_vma->vm_flags & VM_SHARED; ssize_t err; pte_t *dst_pte; unsigned long src_addr, dst_addr; @@ -380,7 +483,7 @@ 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); + uffd_mfill_unlock(dst_vma); return -EINVAL; } @@ -403,24 +506,28 @@ static __always_inline ssize_t mfill_atomic_hugetlb( * retry, dst_vma will be set to NULL and we must lookup again. */ if (!dst_vma) { + dst_vma = uffd_mfill_lock(dst_mm, dst_start, len); + if (IS_ERR(dst_vma)) { + err = PTR_ERR(dst_vma); + goto out; + } + err = -ENOENT; - dst_vma = find_dst_vma(dst_mm, dst_start, len); - if (!dst_vma || !is_vm_hugetlb_page(dst_vma)) - goto out_unlock; + if (!is_vm_hugetlb_page(dst_vma)) + goto out_unlock_vma; err = -EINVAL; if (vma_hpagesize != vma_kernel_pagesize(dst_vma)) - goto out_unlock; - - vm_shared = dst_vma->vm_flags & VM_SHARED; - } + goto out_unlock_vma; - /* - * If not shared, ensure the dst_vma has a anon_vma. - */ - err = -ENOMEM; - if (!vm_shared) { - if (unlikely(anon_vma_prepare(dst_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; } @@ -465,7 +572,7 @@ static __always_inline ssize_t mfill_atomic_hugetlb( if (unlikely(err == -ENOENT)) { up_read(&ctx->map_changing_lock); - mmap_read_unlock(dst_mm); + uffd_mfill_unlock(dst_vma); BUG_ON(!folio); err = copy_folio_from_user(folio, @@ -474,17 +581,6 @@ 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 +601,8 @@ static __always_inline ssize_t mfill_atomic_hugetlb( out_unlock: up_read(&ctx->map_changing_lock); - mmap_read_unlock(dst_mm); +out_unlock_vma: + uffd_mfill_unlock(dst_vma); out: if (folio) folio_put(folio); @@ -597,7 +694,15 @@ 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. + */ + dst_vma = uffd_mfill_lock(dst_mm, dst_start, len); + if (IS_ERR(dst_vma)) { + err = PTR_ERR(dst_vma); + goto out; + } /* * If memory mappings are changing because of non-cooperative @@ -609,15 +714,6 @@ 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 @@ -647,16 +743,6 @@ static __always_inline ssize_t mfill_atomic(struct userfaultfd_ctx *ctx, uffd_flags_mode_is(flags, MFILL_ATOMIC_CONTINUE)) goto out_unlock; - /* - * Ensure the dst_vma has a anon_vma or this page - * would get a NULL anon_vma when moved in the - * dst_vma. - */ - err = -ENOMEM; - if (!(dst_vma->vm_flags & VM_SHARED) && - unlikely(anon_vma_prepare(dst_vma))) - goto out_unlock; - while (src_addr < src_start + len) { pmd_t dst_pmdval; @@ -699,7 +785,7 @@ static __always_inline ssize_t mfill_atomic(struct userfaultfd_ctx *ctx, void *kaddr; up_read(&ctx->map_changing_lock); - mmap_read_unlock(dst_mm); + uffd_mfill_unlock(dst_vma); BUG_ON(!folio); kaddr = kmap_local_folio(folio, 0); @@ -730,7 +816,7 @@ static __always_inline ssize_t mfill_atomic(struct userfaultfd_ctx *ctx, out_unlock: up_read(&ctx->map_changing_lock); - mmap_read_unlock(dst_mm); + uffd_mfill_unlock(dst_vma); out: if (folio) folio_put(folio); @@ -1267,27 +1353,136 @@ static int validate_move_areas(struct userfaultfd_ctx *ctx, if (!vma_is_anonymous(src_vma) || !vma_is_anonymous(dst_vma)) return -EINVAL; + return 0; +} + +static __always_inline +int find_vmas_mm_locked(struct mm_struct *mm, + unsigned long dst_start, + unsigned long src_start, + struct vm_area_struct **dst_vmap, + struct vm_area_struct **src_vmap) +{ + struct vm_area_struct *vma; + + mmap_assert_locked(mm); + vma = find_vma_and_prepare_anon(mm, dst_start); + if (IS_ERR(vma)) + return PTR_ERR(vma); + + *dst_vmap = vma; + /* Skip finding src_vma if src_start is in dst_vma */ + if (src_start >= vma->vm_start && src_start < vma->vm_end) + goto out_success; + + vma = vma_lookup(mm, src_start); + if (!vma) + return -ENOENT; +out_success: + *src_vmap = vma; + return 0; +} + +#ifdef CONFIG_PER_VMA_LOCK +static int uffd_move_lock(struct mm_struct *mm, + unsigned long dst_start, + unsigned long src_start, + struct vm_area_struct **dst_vmap, + struct vm_area_struct **src_vmap) +{ + struct vm_area_struct *vma; + int err; + + vma = lock_vma(mm, dst_start); + if (IS_ERR(vma)) + return PTR_ERR(vma); + + *dst_vmap = vma; /* - * Ensure the dst_vma has a anon_vma or this page - * would get a NULL anon_vma when moved in the - * dst_vma. + * Skip finding src_vma if src_start is in dst_vma. This also ensures + * that we don't lock the same vma twice. */ - if (unlikely(anon_vma_prepare(dst_vma))) - return -ENOMEM; + if (src_start >= vma->vm_start && src_start < vma->vm_end) { + *src_vmap = vma; + return 0; + } - return 0; + /* + * Using lock_vma() to get src_vma can lead to following deadlock: + * + * Thread1 Thread2 + * ------- ------- + * vma_start_read(dst_vma) + * mmap_write_lock(mm) + * vma_start_write(src_vma) + * vma_start_read(src_vma) + * mmap_read_lock(mm) + * vma_start_write(dst_vma) + */ + *src_vmap = lock_vma_under_rcu(mm, src_start); + if (likely(*src_vmap)) + return 0; + + /* Undo any locking and retry in mmap_lock critical section */ + vma_end_read(*dst_vmap); + + mmap_read_lock(mm); + err = find_vmas_mm_locked(mm, dst_start, src_start, dst_vmap, src_vmap); + if (!err) { + /* + * See comment in lock_vma() as to why not using + * vma_start_read() here. + */ + down_read(&(*dst_vmap)->vm_lock->lock); + if (*dst_vmap != *src_vmap) + down_read(&(*src_vmap)->vm_lock->lock); + } + mmap_read_unlock(mm); + return err; +} + +static void uffd_move_unlock(struct vm_area_struct *dst_vma, + struct vm_area_struct *src_vma) +{ + vma_end_read(src_vma); + if (src_vma != dst_vma) + vma_end_read(dst_vma); } +#else + +static int uffd_move_lock(struct mm_struct *mm, + unsigned long dst_start, + unsigned long src_start, + struct vm_area_struct **dst_vmap, + struct vm_area_struct **src_vmap) +{ + int err; + + mmap_read_lock(mm); + err = find_vmas_mm_locked(mm, dst_start, src_start, dst_vmap, src_vmap); + if (err) + mmap_read_unlock(mm); + return err; +} + +static void uffd_move_unlock(struct vm_area_struct *dst_vma, + struct vm_area_struct *src_vma) +{ + mmap_assert_locked(src_vma->vm_mm); + mmap_read_unlock(dst_vma->vm_mm); +} +#endif + /** * move_pages - move arbitrary anonymous pages of an existing vma * @ctx: pointer to the userfaultfd context - * @mm: the address space to move pages * @dst_start: start of the destination virtual memory range * @src_start: start of the source virtual memory range * @len: length of the virtual memory range * @mode: flags from uffdio_move.mode * - * Must be called with mmap_lock held for read. + * It will either use the mmap_lock in read mode or per-vma locks * * move_pages() remaps arbitrary anonymous pages atomically in zero * copy. It only works on non shared anonymous pages because those can @@ -1355,10 +1550,10 @@ 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; @@ -1376,28 +1571,34 @@ ssize_t move_pages(struct userfaultfd_ctx *ctx, struct mm_struct *mm, WARN_ON_ONCE(dst_start + len <= dst_start)) goto out; + err = uffd_move_lock(mm, dst_start, src_start, &dst_vma, &src_vma); + if (err) + goto out; + + /* Re-check after taking map_changing_lock */ + err = -EAGAIN; + down_read(&ctx->map_changing_lock); + if (likely(atomic_read(&ctx->mmap_changing))) + 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_start < src_vma->vm_start || - src_start + len > src_vma->vm_end) - goto out; + err = -EINVAL; + if (src_vma->vm_flags & VM_SHARED) + goto out_unlock; + if (src_start + len > src_vma->vm_end) + goto out_unlock; - dst_vma = find_vma(mm, dst_start); - if (!dst_vma || (dst_vma->vm_flags & VM_SHARED)) - goto out; - if (dst_start < dst_vma->vm_start || - dst_start + len > dst_vma->vm_end) - goto out; + if (dst_vma->vm_flags & VM_SHARED) + goto out_unlock; + if (dst_start + len > dst_vma->vm_end) + 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;) { @@ -1514,6 +1715,9 @@ ssize_t move_pages(struct userfaultfd_ctx *ctx, struct mm_struct *mm, moved += step_size; } +out_unlock: + up_read(&ctx->map_changing_lock); + uffd_move_unlock(dst_vma, src_vma); out: VM_WARN_ON(moved < 0); VM_WARN_ON(err > 0);