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b=0jq/9Qyqvev3SfPJwJcvNW8LTEnzWab/6cRd9shWI9urOkdwxu1yIruaSExNiafPd Fpqz4beoIGVnXN+QIEEUJmWPIPi/yUmQP0SnWn7pTVyxu4nGyQnMc3vt35dPxmDbWq sOhqhI0EDjZzkff2mD4D7gij31/aq/uSc8+hArEo= Date: Thu, 21 Mar 2024 17:47:42 -0700 From: Andrew Morton To: Lokesh Gidra Cc: linux-mm@kvack.org, linux-kernel@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, jannh@google.com, kaleshsingh@google.com, ngeoffray@google.com, rppt@kernel.org, hdanton@sina.com, syzbot+49056626fe41e01f2ba7@syzkaller.appspotmail.com Subject: Re: [PATCH] userfaultfd: fix deadlock warning when locking src and dst VMAs Message-Id: <20240321174742.6c5622f4406673629e266db7@linux-foundation.org> In-Reply-To: <20240321235818.125118-1-lokeshgidra@google.com> References: <20240321235818.125118-1-lokeshgidra@google.com> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: C26DD40009 X-Stat-Signature: 8c7xhdpqac9thxjx6etafhbbdyjdkrzp X-HE-Tag: 1711068464-986608 X-HE-Meta: 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 KLLt0xm8 Xspb10f0NQWMN5rhnL28Fbp8vaq7kzcAfgJ0DOIEaplQgQ9JX+Hw4aXpiTf5kAoGoiApIyhyubOWWclBVA5+DeqHLk8ZUq95lVV3u0z/jtXBLrHGU8s1DfrBTGJGZkV8n8qyPPv/4PajeyInc8GfnhBqtw6CQjJMxAoHcHhaio5BJQuRvXOQuj4CtL03M7C6sVPAcPOtuwMyE9tuPimUmoZaDsET7/q6qgcvV12Kj0EExqFRTPvnbk+3dq3Hn6y3EpkMr4umIFByytgqhqTA66CMP6sit5lWkiRhIFzjZhoPg2aArKNvCNPWYJ5Mvkuj4kpHOQwgXpPrnesmF4+tSJtf+n+vufR24tdr+FS4cloBKjIbpcnmq6pLGTg== 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: On Thu, 21 Mar 2024 16:58:18 -0700 Lokesh Gidra wrote: > Use down_read_nested() to avoid the warning. > > --- a/mm/userfaultfd.c > +++ b/mm/userfaultfd.c > @@ -1444,7 +1444,8 @@ static int uffd_move_lock(struct mm_struct *mm, > */ > down_read(&(*dst_vmap)->vm_lock->lock); > if (*dst_vmap != *src_vmap) > - down_read(&(*src_vmap)->vm_lock->lock); > + down_read_nested(&(*src_vmap)->vm_lock->lock, > + SINGLE_DEPTH_NESTING); > } > mmap_read_unlock(mm); > return err; Thanks, I added Fixes: 867a43a34ff8a ("userfaultfd: use per-vma locks in userfaultfd operations")