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bh=ROrHr4rQEbBVSusuDkPZQbj47+FTbTSpcuR7ZWvb2vc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Tg4+zMABiHi8H6Q/nzPqPNkkol1qGThUhsrluFNxfLCFfR5Q9EvR8bmNktoqY8wF6 xsbM1hVhvV0VbwzXriICD6BAA6dKggq4SmM3JqwDDhgei8Q6reYk8I/OUbkZIh9XJH S+RWr/y/TOipoc19PIAfzkhmNZPvjsBsWcUI/3Bs2cpuWU76lIsnU7eG53sIehYv8X WWhMn7gb7Ugxrg/QtPsKDS+ZOXSfWlF46zLRBx8eR2CO4ClGFnHU9GgM6IgO7En7on hEDdJxEs9YjUc1KGjYaA4EdbtMymEq/Y4pv+ERyzRRgUsfY6cJeUFtAbby56pZvgnh A8A7VRvup4NWA== From: SeongJae Park To: Matthew Wilcox Cc: SeongJae Park , akpm@linux-foundation.org, alexander.h.duyck@linux.intel.com, paulmck@kernel.org, linux-mm@kvack.org, rcu@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm/page_reporting: replace rcu_access_pointer() with rcu_dereference_protected() Date: Tue, 27 Dec 2022 19:56:59 +0000 Message-Id: <20221227195659.2876-1-sj@kernel.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 443D5120003 X-Stat-Signature: gfzzobq7enpextcc5mz6cmpkbxt698cr X-Rspam-User: X-HE-Tag: 1672171025-591175 X-HE-Meta: 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 HIMwy3nA QyKEkeHBueXQWu5O6thfNHYHsjYxlPLJxTZKmAvewpTURh1MU/6HXWgLhPUqy3BzRms2d7QnfvTKdbVZqCR6h7oOE2ZLHeFHGQ/+GFRo6PWAvIRTRv+VRnFfQdg== 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 Tue, 27 Dec 2022 19:55:09 +0000 Matthew Wilcox wrote: > On Tue, Dec 27, 2022 at 07:21:58PM +0000, SeongJae Park wrote: > > +++ b/mm/page_reporting.c > > @@ -356,7 +356,7 @@ int page_reporting_register(struct page_reporting_dev_info *prdev) > > mutex_lock(&page_reporting_mutex); > > > > /* nothing to do if already in use */ > > - if (rcu_access_pointer(pr_dev_info)) { > > + if (rcu_dereference_protected(pr_dev_info, true)) { > > Pretty sure that passing a bare 'true' is an antipattern. > Instead, document _what_ lock protects us, ie: > > if (rcu_dereference_protected(pr_dev_info, > lockdep_is_held(&page_reporting_mutex))) { > > Obviously, we took it just one line up, but if code moves around, it > may save us. Good point, agreed. Will do so in the next version. Thanks, SJ