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 2D4C6143888 for ; Thu, 9 Jan 2025 05:44:31 +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=1736401472; cv=none; b=kQOx2ZZtA0kADl5LqNp03VnRMCVvkhSKLR1Uk5RrxYoGVvYMXhsYBC+jxeBVdWVoPvL+qhd0B4e5xoWgecGa6FqWRghSkXaUG4lrNBfVB6BZ++ykZ3PkjETeomiwpXtZYlD1vnPxUD7hq12P7jrBMHcyrmrtXo3nylIcIXfvy3c= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1736401472; c=relaxed/simple; bh=XyFoWil4zQV/7jBUtbjIcq4+eQCaICdYRLAtCCSLXR8=; h=Date:To:From:Subject:Message-Id; b=AnQAbWcK1Y/yp7whMxctBcKpyfzoUM2lbfNtiInLLlYxBJlHwM1BCGTF1aW1lYqPiHfqgeRVAHjtKbSGojHrPt1tm84PumLqGbrOax1kMLj+cynqHhWx6ZQq6NNYxsgf4srua5DOe8/cx4N/e2nwv4q786mVT5nZwdjrLRDAyBc= 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=WEbpdMx1; 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="WEbpdMx1" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A1281C4CED2; Thu, 9 Jan 2025 05:44:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1736401471; bh=XyFoWil4zQV/7jBUtbjIcq4+eQCaICdYRLAtCCSLXR8=; h=Date:To:From:Subject:From; b=WEbpdMx1CtzM9xC/75JVwKpzg3ujnptU+FobWjR1UNJYEKJs9LKNiW58bDlZY0O// LglOHf8B+5M3mhR9dzU3S81AhmIMyinJp73uHrcfQUz9x2mLQ95kF2nZJQ7UTtsUvA kIwltldu6peUGXieoHdzMm1PtDF1n0XxKcKbcdB8= Date: Wed, 08 Jan 2025 21:44:31 -0800 To: mm-commits@vger.kernel.org,willy@infradead.org,vbabka@suse.cz,souravpanda@google.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: <20250109054431.A1281C4CED2@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: Wed, 8 Jan 2025 18:30:16 -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/20250109023025.2242447-8-surenb@google.com Signed-off-by: Suren Baghdasaryan Acked-by: Vlastimil Babka Cc: Lokesh Gidra Cc: Christian Brauner Cc: David Hildenbrand Cc: David Howells Cc: Davidlohr Bueso Cc: Hillf Danton Cc: Hugh Dickins 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 (Oracle) 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 Cc: Shakeel Butt Cc: Sourav Panda Cc: Wei Yang Signed-off-by: Andrew Morton --- include/linux/mm.h | 6 ++++-- mm/userfaultfd.c | 18 +++++++++++++----- 2 files changed, 17 insertions(+), 7 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 @@ -85,7 +85,8 @@ 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 (!vma_start_read_locked(vma)) + vma = ERR_PTR(-EAGAIN); mmap_read_unlock(mm); return vma; @@ -1483,10 +1484,17 @@ 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 (vma_start_read_locked(*dst_vmap)) { + if (*dst_vmap != *src_vmap) { + if (!vma_start_read_locked_nested(*src_vmap, + SINGLE_DEPTH_NESTING)) { + vma_end_read(*dst_vmap); + err = -EAGAIN; + } + } + } else { + err = -EAGAIN; + } } mmap_read_unlock(mm); return err; _ Patches currently in -mm which might be from surenb@google.com are alloc_tag-skip-pgalloc_tag_swap-if-profiling-is-disabled.patch tools-fix-atomic_set-definition-to-set-the-value-correctly.patch seqlock-add-raw_seqcount_try_begin.patch mm-convert-mm_lock_seq-to-a-proper-seqcount.patch mm-introduce-mmap_lock_speculate_try_beginretry.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-introduce-__refcount_addinc_not_zero_limited.patch mm-replace-vm_lock-and-detached-flag-with-a-reference-count.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 alloc_tag-avoid-current-alloc_tag-manipulations-when-profiling-is-disabled.patch