From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 5A1BA3FBB3 for ; Sat, 15 Feb 2025 00:42:19 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1739580139; cv=none; b=mIuh7nYwS+jCdiT9FDChihFMv/sSgAuiDaV8aBYtuMtS7Vzl5sn8imoijSgpS9p4qptAhN2DwGHlm1L1UkpmfWi9ZVEX8aCuhiXai8X5buGGPJyfgLel/bbKJjD9LdyVXDacxwSh3DctQg3F9ZGhPjZE4P1TLGMvd38APvCcbGU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1739580139; c=relaxed/simple; bh=/WJ3jk3eOSvzQqyrNIMyP6im6ZjCfqWBDJL48iskZVc=; h=Date:To:From:Subject:Message-Id; b=ZWwuJ34+bL9YxSEridR5SiiCaChViPWswznp3zzJLzFWF7MDfpif891udli60t8Ys7XiWjBVk83tNYXwvOzrHgA9TNipWzAOwAmJHkmII2BYEbswN9bPAqgjmw2ge4g8aHT/NOgzvyscW9moVPfHR7rHT9JhRMsa5hOa98Mf9G8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b=m4w8Qj1p; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="m4w8Qj1p" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 15947C4CED1; Sat, 15 Feb 2025 00:42:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1739580139; bh=/WJ3jk3eOSvzQqyrNIMyP6im6ZjCfqWBDJL48iskZVc=; h=Date:To:From:Subject:From; b=m4w8Qj1pRU6lsWFkgJKqtlVEp+sd/nJL4/J7gOhGlg1Z7wanqCR/Xn08nQXZwCU9+ f2RTt5GhEHdX2D/nyT1F+godZW8TNVrJe4u0Vr7rsXERUQOkymNmVb+YluzelBCmcL HNVue44vyWrdQoShCe9oHguffvQAvIrkWPz99GuA= Date: Fri, 14 Feb 2025 16:42:18 -0800 To: mm-commits@vger.kernel.org,willy@infradead.org,will@kernel.org,vbabka@suse.cz,souravpanda@google.com,shivankg@amd.com,shakeel.butt@linux.dev,richard.weiyang@gmail.com,peterz@infradead.org,peterx@redhat.com,paulmck@kernel.org,pasha.tatashin@soleen.com,oleg@redhat.com,mjguzik@gmail.com,minchan@google.com,mhocko@suse.com,mgorman@techsingularity.net,lorenzo.stoakes@oracle.com,lokeshgidra@google.com,Liam.Howlett@Oracle.com,klarasmodin@gmail.com,jannh@google.com,hughd@google.com,hdanton@sina.com,hannes@cmpxchg.org,dhowells@redhat.com,david@redhat.com,dave@stgolabs.net,corbet@lwn.net,brauner@kernel.org,surenb@google.com,akpm@linux-foundation.org From: Andrew Morton Subject: + mm-allow-vma_start_read_locked-vma_start_read_locked_nested-to-fail.patch added to mm-unstable branch Message-Id: <20250215004219.15947C4CED1@smtp.kernel.org> Precedence: bulk X-Mailing-List: mm-commits@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: The patch titled Subject: mm: allow vma_start_read_locked/vma_start_read_locked_nested to fail has been added to the -mm mm-unstable branch. Its filename is mm-allow-vma_start_read_locked-vma_start_read_locked_nested-to-fail.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-allow-vma_start_read_locked-vma_start_read_locked_nested-to-fail.patch This patch will later appear in the mm-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next via the mm-everything branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm and is updated there every 2-3 working days ------------------------------------------------------ From: Suren Baghdasaryan Subject: mm: allow vma_start_read_locked/vma_start_read_locked_nested to fail Date: Thu, 13 Feb 2025 14:46:44 -0800 With upcoming replacement of vm_lock with vm_refcnt, we need to handle a possibility of vma_start_read_locked/vma_start_read_locked_nested failing due to refcount overflow. Prepare for such possibility by changing these APIs and adjusting their users. Link: https://lkml.kernel.org/r/20250213224655.1680278-8-surenb@google.com Signed-off-by: Suren Baghdasaryan Cc: Lokesh Gidra Tested-by: Shivank Garg Link: https://lkml.kernel.org/r/5e19ec93-8307-47c2-bb13-3ddf7150624e@amd.com Cc: Christian Brauner Cc: David Hildenbrand Cc: David Howells Cc: Davidlohr Bueso Cc: Hillf Danton Cc: Hugh Dickens Cc: Jann Horn Cc: Johannes Weiner Cc: Jonathan Corbet Cc: Klara Modin Cc: Liam R. Howlett Cc: Lorenzo Stoakes Cc: Mateusz Guzik Cc: Matthew Wilcox Cc: Mel Gorman Cc: Michal Hocko Cc: Minchan Kim Cc: Oleg Nesterov Cc: Pasha Tatashin Cc: "Paul E . McKenney" Cc: Peter Xu Cc: Peter Zijlstra (Intel) Cc: Shakeel Butt Cc: Sourav Panda Cc: Vlastimil Babka Cc: Wei Yang Cc: Will Deacon Signed-off-by: Andrew Morton --- include/linux/mm.h | 6 ++++-- mm/userfaultfd.c | 30 +++++++++++++++++++++++------- 2 files changed, 27 insertions(+), 9 deletions(-) --- a/include/linux/mm.h~mm-allow-vma_start_read_locked-vma_start_read_locked_nested-to-fail +++ a/include/linux/mm.h @@ -747,10 +747,11 @@ static inline bool vma_start_read(struct * not be used in such cases because it might fail due to mm_lock_seq overflow. * This functionality is used to obtain vma read lock and drop the mmap read lock. */ -static inline void vma_start_read_locked_nested(struct vm_area_struct *vma, int subclass) +static inline bool vma_start_read_locked_nested(struct vm_area_struct *vma, int subclass) { mmap_assert_locked(vma->vm_mm); down_read_nested(&vma->vm_lock.lock, subclass); + return true; } /* @@ -759,10 +760,11 @@ static inline void vma_start_read_locked * not be used in such cases because it might fail due to mm_lock_seq overflow. * This functionality is used to obtain vma read lock and drop the mmap read lock. */ -static inline void vma_start_read_locked(struct vm_area_struct *vma) +static inline bool vma_start_read_locked(struct vm_area_struct *vma) { mmap_assert_locked(vma->vm_mm); down_read(&vma->vm_lock.lock); + return true; } static inline void vma_end_read(struct vm_area_struct *vma) --- a/mm/userfaultfd.c~mm-allow-vma_start_read_locked-vma_start_read_locked_nested-to-fail +++ a/mm/userfaultfd.c @@ -84,8 +84,12 @@ static struct vm_area_struct *uffd_lock_ mmap_read_lock(mm); vma = find_vma_and_prepare_anon(mm, address); - if (!IS_ERR(vma)) - vma_start_read_locked(vma); + if (!IS_ERR(vma)) { + bool locked = vma_start_read_locked(vma); + + if (!locked) + vma = ERR_PTR(-EAGAIN); + } mmap_read_unlock(mm); return vma; @@ -1482,12 +1486,24 @@ static int uffd_move_lock(struct mm_stru mmap_read_lock(mm); err = find_vmas_mm_locked(mm, dst_start, src_start, dst_vmap, src_vmap); - if (!err) { - vma_start_read_locked(*dst_vmap); - if (*dst_vmap != *src_vmap) - vma_start_read_locked_nested(*src_vmap, - SINGLE_DEPTH_NESTING); + if (err) + goto out; + + if (!vma_start_read_locked(*dst_vmap)) { + err = -EAGAIN; + goto out; } + + /* Nothing further to do if both vmas are locked. */ + if (*dst_vmap == *src_vmap) + goto out; + + if (!vma_start_read_locked_nested(*src_vmap, SINGLE_DEPTH_NESTING)) { + /* Undo dst_vmap locking if src_vmap failed to lock */ + vma_end_read(*dst_vmap); + err = -EAGAIN; + } +out: mmap_read_unlock(mm); return err; } _ Patches currently in -mm which might be from surenb@google.com are alloc_tag-work-around-clang-14-issue-with-__builtin_object_size.patch mm-avoid-extra-mem_alloc_profiling_enabled-checks.patch alloc_tag-uninline-code-gated-by-mem_alloc_profiling_key-in-slab-allocator.patch alloc_tag-uninline-code-gated-by-mem_alloc_profiling_key-in-page-allocator.patch mm-introduce-vma_start_read_locked_nested-helpers.patch mm-move-per-vma-lock-into-vm_area_struct.patch mm-mark-vma-as-detached-until-its-added-into-vma-tree.patch mm-introduce-vma_iter_store_attached-to-use-with-attached-vmas.patch mm-mark-vmas-detached-upon-exit.patch types-move-struct-rcuwait-into-typesh.patch mm-allow-vma_start_read_locked-vma_start_read_locked_nested-to-fail.patch mm-move-mmap_init_lock-out-of-the-header-file.patch mm-uninline-the-main-body-of-vma_start_write.patch refcount-provide-ops-for-cases-when-objects-memory-can-be-reused.patch refcount-introduce-__refcount_addinc_not_zero_limited_acquire.patch mm-replace-vm_lock-and-detached-flag-with-a-reference-count.patch mm-move-lesser-used-vma_area_struct-members-into-the-last-cacheline.patch mm-debug-print-vm_refcnt-state-when-dumping-the-vma.patch mm-remove-extra-vma_numab_state_init-call.patch mm-prepare-lock_vma_under_rcu-for-vma-reuse-possibility.patch mm-make-vma-cache-slab_typesafe_by_rcu.patch docs-mm-document-latest-changes-to-vm_lock.patch