diff options
| author | SeongJae Park <sj@kernel.org> | 2022-12-28 17:59:42 +0000 |
|---|---|---|
| committer | Andrew Morton <akpm@linux-foundation.org> | 2023-01-18 17:12:50 -0800 |
| commit | 01b5022f0a8a2911bb8f2bc3f0c9b9b2c21c3316 (patch) | |
| tree | 5b358fd606e1fe2fbb9adad9ef52d7fdecc97ad1 /mm/page_reporting.c | |
| parent | 3783e1721b650588938d28e4a084a1c9748361c8 (diff) | |
mm/page_reporting: replace rcu_access_pointer() with rcu_dereference_protected()
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 fetching it using rcu_access_pointer(), but it fetches the pointer
while concurrent updates to the pointer is avoided by holding the update
side lock, page_reporting_mutex.
In the case, rcu_dereference_protected() should be used instead 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().
Link: https://lkml.kernel.org/r/20221228175942.149491-1-sj@kernel.org
Fixes: 36e66c554b5c ("mm: introduce Reported pages")
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Alexander Duyck <alexander.h.duyck@linux.intel.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'mm/page_reporting.c')
| -rw-r--r-- | mm/page_reporting.c | 6 |
1 files changed, 4 insertions, 2 deletions
diff --git a/mm/page_reporting.c b/mm/page_reporting.c index 79a8554f024c..c65813a9dc78 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_mutex))) { err = -EBUSY; goto err_out; } @@ -401,7 +402,8 @@ void page_reporting_unregister(struct page_reporting_dev_info *prdev) { mutex_lock(&page_reporting_mutex); - if (rcu_access_pointer(pr_dev_info) == prdev) { + if (prdev == rcu_dereference_protected(pr_dev_info, + lockdep_is_held(&page_reporting_mutex))) { /* Disable page reporting notification */ RCU_INIT_POINTER(pr_dev_info, NULL); synchronize_rcu(); |