From: Sebastian Andrzej Siewior <bigeasy@linutronix.de> mainline inclusion from mainline-v6.15-rc1 commit 328152e6774d9d801ad1d90af557b9113647b379 category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/IC97W5 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... ---------------------------------------------------------------------- get_ucounts_or_wrap() increments the counter and if the counter is negative then it decrements it again in order to reset the previous increment. This statement can be replaced with atomic_inc_not_zero() to only increment the counter if it is not yet 0. This simplifies the get function because the put (if the get failed) can be removed. atomic_inc_not_zero() is implement as a cmpxchg() loop which can be repeated several times if another get/put is performed in parallel. This will be optimized later. Increment the reference counter only if not yet dropped to zero. Link: https://lkml.kernel.org/r/20250203150525.456525-3-bigeasy@linutronix.de Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Reviewed-by: Paul E. McKenney <paulmck@kernel.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Boqun Feng <boqun.feng@gmail.com> Cc: Joel Fernandes <joel@joelfernandes.org> Cc: Josh Triplett <josh@joshtriplett.org> Cc: Lai jiangshan <jiangshanlai@gmail.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Mengen Sun <mengensun@tencent.com> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: "Uladzislau Rezki (Sony)" <urezki@gmail.com> Cc: YueHong Wu <yuehongwu@tencent.com> Cc: Zqiang <qiang.zhang1211@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Chen Ridong <chenridong@huawei.com> --- kernel/ucount.c | 24 ++++++------------------ 1 file changed, 6 insertions(+), 18 deletions(-) diff --git a/kernel/ucount.c b/kernel/ucount.c index 2c929c6c4784c..797e6479dd914 100644 --- a/kernel/ucount.c +++ b/kernel/ucount.c @@ -151,25 +151,16 @@ static void hlist_add_ucounts(struct ucounts *ucounts) spin_unlock_irq(&ucounts_lock); } -static inline bool get_ucounts_or_wrap(struct ucounts *ucounts) -{ - /* Returns true on a successful get, false if the count wraps. */ - return !atomic_add_negative(1, &ucounts->count); -} - struct ucounts *get_ucounts(struct ucounts *ucounts) { - if (!get_ucounts_or_wrap(ucounts)) { - put_ucounts(ucounts); - ucounts = NULL; - } - return ucounts; + if (atomic_inc_not_zero(&ucounts->count)) + return ucounts; + return NULL; } struct ucounts *alloc_ucounts(struct user_namespace *ns, kuid_t uid) { struct hlist_head *hashent = ucounts_hashentry(ns, uid); - bool wrapped; struct ucounts *ucounts, *new = NULL; spin_lock_irq(&ucounts_lock); @@ -194,14 +185,11 @@ struct ucounts *alloc_ucounts(struct user_namespace *ns, kuid_t uid) return new; } } - - wrapped = !get_ucounts_or_wrap(ucounts); + if (!atomic_inc_not_zero(&ucounts->count)) + ucounts = NULL; spin_unlock_irq(&ucounts_lock); kfree(new); - if (wrapped) { - put_ucounts(ucounts); - return NULL; - } + return ucounts; } -- 2.34.1