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Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.6.0 MIME-Version: 1.0 In-Reply-To: <20221228012902.1510901-1-sj@kernel.org> Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.174.151.185] X-ClientProxiedBy: dggems702-chm.china.huawei.com (10.3.19.179) To canpemm500002.china.huawei.com (7.192.104.244) X-CFilter-Loop: Reflected X-Rspam-User: X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 1BD431C0003 X-Stat-Signature: xzmizoyp7ox6tg4jiacrkpesujaibkaw X-HE-Tag: 1672191905-192788 X-HE-Meta: U2FsdGVkX18Wg4DAhVs/z53QLdy/1xvDOmaQQoBbyJIhcVDC32K4pk3TqPPXlDLJ67wE9Mhn43u+JwGaPgBjShgjhE6z1bcMmSdWJF8ewNeSdOV4ceQVpObTKR1iZ1r7s8/iTpqoSHpTUxHceeSp0eKeKJLGF0kTBELXXam9h12QX46KU+e3AlrCCm9c+ZhHCmLZnIpggowLQmA3sFn3XAoniZK0iSt6wNFEWMGhCNNE4SOkOmZ2LqG1VoXV2aAG2eip4UF1IPP0lItk17v9GPVUq8XOSvdtXw5k6Dmt9UCQmnIe4jDpxW+NjREeoKWw/+s30Gtdd/hFYFVCEnTrXdAalC94ob6MSLu/tCwSC73Bw5eO+j11DSDoUIYjcVu3vsSWjB3CDNZLOGsZ49c84SqCOprTHjMliDgpYQZUpYiGHzfhf9GW0Qybxb5wRzbXk+4Is2K9VZyQ77qMdHxQXyf47fdDVfATdrpTCSH6cM4GIiFu6v1pviYrkK2YLGHYv9W+mQlFVTYaKsX+mvyrJ3jDz+YAGiLAjMoIsA+AfjvtSJVsqUp1TEfYL+hgW3Rz2+2rUz2383yZ9D2I5xHPKm8Z+p5aPishUxZZ/qqeehwXhCIVCHhcah0Yz1blotMcM9fVkgcaaddnXfYTeqSXKr3gt8Mtf0wJMkcj/jdr3rXYUXflLzfa7VQloJMx769fhQpe5F3yysDGGyXoEq9vYNHIGIs985It24L0cMgcDIX8BDDWedm+ftfRE3kZxZDvjNiCnG+GZS9gR0skE8e8RxqRG2licIo+LZM7Kx56WlBbZjDvuoM8mrz3Xuyai08ENcde81xDgBmiRM1XR/zhizeBMJQ7F8c8xFzLZ+K2F6IbAgLtHMc6kQ== 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 2022/12/28 9:29, SeongJae Park wrote: > Page reporting fetches pr_dev_info using rcu_access_pointer(), which is > for safely fetching a pointer that will not be dereferenced but could > concurrently updated. The code indeed does not dereference pr_dev_info > after fetcing it using rcu_access_pointer(), but it fetches the pointer Thanks for your work. Might something to improve. s/fetcing/fetching/ > while concurrent updtes to the pointer is avoided by holding the update s/updtes/updates/ > side lock, page_reporting_mutex. > > In the case, rcu_dereference_protected() is recommended because it > provides better readability and performance on some cases, as > rcu_dereference_protected() avoids use of READ_ONCE(). Replace the > rcu_access_pointer() calls with rcu_dereference_protected(). > > Signed-off-by: SeongJae Park > --- > Changes from v1 > (https://lore.kernel.org/linux-mm/20221227192158.2553-1-sj@kernel.org/) > - Explicitly set the protection condition (Matthew Wilcox) > > mm/page_reporting.c | 6 ++++-- > 1 file changed, 4 insertions(+), 2 deletions(-) > > diff --git a/mm/page_reporting.c b/mm/page_reporting.c > index 79a8554f024c..5c557a3e1423 100644 > --- a/mm/page_reporting.c > +++ b/mm/page_reporting.c > @@ -356,7 +356,8 @@ 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, > + lockdep_is_held(&page_reporting_order))) { I think it should be lockdep_is_held(&page_reporting_mutex) instead of lockdep_is_held(&page_reporting_order) here? Thanks, Miaohe Lin