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Wed, 28 Jun 2023 17:19:42 -0700 (PDT) MIME-Version: 1.0 References: <20230628172529.744839-1-surenb@google.com> <20230628172529.744839-7-surenb@google.com> In-Reply-To: From: Suren Baghdasaryan Date: Wed, 28 Jun 2023 17:19:31 -0700 Message-ID: Subject: Re: [PATCH v5 6/6] mm: handle userfaults under VMA lock To: Peter Xu Cc: akpm@linux-foundation.org, willy@infradead.org, hannes@cmpxchg.org, mhocko@suse.com, josef@toxicpanda.com, jack@suse.cz, ldufour@linux.ibm.com, laurent.dufour@fr.ibm.com, michel@lespinasse.org, liam.howlett@oracle.com, jglisse@google.com, vbabka@suse.cz, minchan@google.com, dave@stgolabs.net, punit.agrawal@bytedance.com, lstoakes@gmail.com, hdanton@sina.com, apopple@nvidia.com, ying.huang@intel.com, david@redhat.com, yuzhao@google.com, dhowells@redhat.com, hughd@google.com, viro@zeniv.linux.org.uk, brauner@kernel.org, pasha.tatashin@soleen.com, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-team@android.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 492EAC0012 X-Stat-Signature: 3bcqfx7gd8ke8yzmfu4dww7435r9eyxu X-Rspam-User: X-HE-Tag: 1687997983-804353 X-HE-Meta: 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 gVtNszW8 ugQjq9P78EODB8QSOysmPzXrXSTwuzURGCi3J7d6bWspU/vO9UaBxVn6GT41DuKnq1YKfdE80cexHlLDyh3inBMO4r0QzWvkYz/nvigJvDKqhLjoUEbBlh8RpcMmhbicUJxT6iKzPWl4aAavwEAq3/HpQrNE9k3NZ7gfCUTUcucaukf94ztYi9KQvyScWOAY3Bn5ztYR7oUKxnOGzqZ5eANuT6K9gY92lfQMRN1SakOzJFuj06j6N5DmGGVCe+xs1Gur1LPLG/642PCOM3CioA7BDrQ== 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: On Wed, Jun 28, 2023 at 10:32=E2=80=AFAM Peter Xu wrote= : > > On Wed, Jun 28, 2023 at 10:25:29AM -0700, Suren Baghdasaryan wrote: > > Enable handle_userfault to operate under VMA lock by releasing VMA lock > > instead of mmap_lock and retrying. Note that FAULT_FLAG_RETRY_NOWAIT > > should never be used when handling faults under per-VMA lock protection > > because that would break the assumption that lock is dropped on retry. > > > > Signed-off-by: Suren Baghdasaryan > > Maybe the sanitize_fault_flags() changes suite more in patch 3, but not a > big deal I guess. IIUC FAULT_FLAG_RETRY_NOWAIT comes into play in this patchset only in the context of uffds, therefore that check seems to be needed when we enable per-VMA lock uffd support, which is this patch. Does that make sense? > > Acked-by: Peter Xu Thanks! > > Thanks! > > -- > Peter Xu >