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b=vvT/rQWzgJDr0V2xCe5oJnEkWOZJd3d2v4R5+z3ox1UnBdFPL8z47NK2/qafJ9FW5 W88A6MQWdUKe4MXiyYhJ8B/oPx/N3+C3OtecFrwPa7evbKBxKv5QIfACKONpkZS9OK vNwbAw2PxEb+WZhrtb8Cx63D1g5eNLyOrfxtNH8s= Date: Thu, 4 Apr 2024 14:23:26 -0700 From: Andrew Morton To: Vishal Verma Cc: Dan Williams , Dave Jiang , Alison Schofield , linux-mm@kvack.org, nvdimm@lists.linux.dev, linux-cxl@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] dax/bus.c: replace WARN_ON_ONCE() with lockdep asserts Message-Id: <20240404142326.b3d5b0f3f7b9f25f1a16288a@linux-foundation.org> In-Reply-To: <20240402-vv-dax_abi_fixes-v1-1-c3e0fdbafba5@intel.com> References: <20240402-vv-dax_abi_fixes-v1-1-c3e0fdbafba5@intel.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: rspam12 X-Rspamd-Queue-Id: 0E7FF100014 X-Stat-Signature: yyrtf3oucj3c1wfhpskb3oj6u6i6a164 X-HE-Tag: 1712265808-871437 X-HE-Meta: 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 IQZ4+zLT 96IMfx3z11ZQcB6H+FK1aH0CQ/6kb/J9oueI3LwtJpNoXB3yh6ots5cr/JhDAZsvBoRcZr+0HNeClOFuEMZWkW9u31mz3EM2bbJG9BtjHEGWeMk6+EJD4gGmT6haa5NG30eGGjEi2NXn0eDi9XGpNerqo4ldTGgRNEgy+Eq+ZulMmMFxvm5vw5SjZOmECOjrirnX5p3VAHtz1um5X8/0Te100cs3sjvO/4w3LBkEbWufaCVcVM53x+MZMDWupjNL78DPzmr/f3GZU/B2ClRiYJyROYkSSGUtd+ycQ9HFz2lqGXzA= 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 Tue, 02 Apr 2024 00:24:28 -0600 Vishal Verma wrote: > In [1], Dan points out that all of the WARN_ON_ONCE() usage in the > referenced patch should be replaced with lockdep_assert_held(_write)(). > > Replace those, and additionally, replace a couple of other > WARN_ON_ONCE() introduced in the same patch for actual failure > cases (i.e. when acquiring a semaphore fails in a remove / unregister > path) with dev_WARN_ONCE() as is the precedent here. > > Recall that previously, unregistration paths was implicitly protected by > overloading the device lock, which the patch in [1] sought to remove. > This meant adding a semaphore acquisition in these unregistration paths. > Since that can fail, and it doesn't make sense to return errors from > these paths, retain the two instances of (now) dev_WARN_ONCE(). > > ... > > @@ -471,6 +471,7 @@ static void __unregister_dev_dax(void *dev) > > dev_dbg(dev, "%s\n", __func__); > > + lockdep_assert_held_write(&dax_region_rwsem); > kill_dev_dax(dev_dax); > device_del(dev); > free_dev_dax_ranges(dev_dax); This is new and unchangelogged? I'm taking Dan's reply to your patch as Not-A-Nack ;)