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 E2BDA215F43 for ; Mon, 17 Mar 2025 05:11:55 +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=1742188316; cv=none; b=EN0zPggFv7lfhXjI7AjFJFyGbJmYA0gy00wwplyPhuB4YrxPpN8oa/TJphHKTt4vOef3O5WTOyh/iFHc6IQZ228S2b96M94rFEfTH52AQZV/+639CjZsPlIq3YW6g1Y7ShU1vRU+rVUHLwBCWkx9OYPJbUSPFqpF9terzteFMMc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1742188316; c=relaxed/simple; bh=DgA0BuI2DBrQaH31eL+VFKxrp4TKQBa2ve1jrAc1F4Q=; h=Date:To:From:Subject:Message-Id; b=PVspSqxKlsRnWgLf1i7eDV5t+BSMjVJ8gdj4T3W+YGOXAD30aEv3BEk7VWkWaoXGDu8ARhAAO35dIKfjdh53RQcu/buTMgNOnNzixCDQbJaDWH6CwpYVe1yxHIB3CGBoEg1EyhzWiHE+LePcEEjDDf9Iczf379VhO+UbjCHy+Gk= 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=X7L+bZvb; 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="X7L+bZvb" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B1D04C4CEEC; Mon, 17 Mar 2025 05:11:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1742188315; bh=DgA0BuI2DBrQaH31eL+VFKxrp4TKQBa2ve1jrAc1F4Q=; h=Date:To:From:Subject:From; b=X7L+bZvb75TsCO5s5XaF7Qrje3H4AoGvUh4Suyj9CenM3Kv9egRF72ekSX+ra9k+W 3KGXSrPQOQzA2sStL3g9j2kpzmRrHJy5KFV3J9uaHASB9WZK7mGxvuwRugQGAXTmjR bZC0clyzbmUv+dsYwLCe6OTHUSGZWiJCGKBec2zY= Date: Sun, 16 Mar 2025 22:11:55 -0700 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,sfr@canb.auug.org.au,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,hca@linux.ibm.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: [merged mm-stable] mm-allow-vma_start_read_locked-vma_start_read_locked_nested-to-fail.patch removed from -mm tree Message-Id: <20250317051155.B1D04C4CEEC@smtp.kernel.org> Precedence: bulk X-Mailing-List: mm-commits@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: The quilt patch titled Subject: mm: allow vma_start_read_locked/vma_start_read_locked_nested to fail has been removed from the -mm tree. Its filename was mm-allow-vma_start_read_locked-vma_start_read_locked_nested-to-fail.patch This patch was dropped because it was merged into the mm-stable branch of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm ------------------------------------------------------ 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 Reviewed-by: Vlastimil Babka Cc: Christian Brauner Cc: David Hildenbrand Cc: David Howells Cc: Davidlohr Bueso 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 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: Wei Yang Cc: Will Deacon Cc: Heiko Carstens Cc: Stephen Rothwell 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 @@ -85,8 +85,12 @@ 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; @@ -1555,12 +1559,24 @@ 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