From 559b3bbfa978ce3b23dc9c52d09a0eddca52c439 Mon Sep 17 00:00:00 2001 From: James Bottomley Date: Thu, 27 Mar 2025 10:06:10 -0400 Subject: locking/percpu-rwsem: add freezable alternative to down_read Percpu-rwsems are used for superblock locking. However, we know the read percpu-rwsem we take for sb_start_write() on a frozen filesystem needs not to inhibit system from suspending or hibernating. That means it needs to wait with TASK_UNINTERRUPTIBLE | TASK_FREEZABLE. Introduce a new percpu_down_read_freezable() that allows us to control whether TASK_FREEZABLE is added to the wait flags. Signed-off-by: James Bottomley Link: https://lore.kernel.org/r/20250327140613.25178-2-James.Bottomley@HansenPartnership.com Signed-off-by: Christian Brauner --- include/linux/percpu-rwsem.h | 20 ++++++++++++++++---- 1 file changed, 16 insertions(+), 4 deletions(-) (limited to 'include/linux') diff --git a/include/linux/percpu-rwsem.h b/include/linux/percpu-rwsem.h index af7d75ede619..288f5235649a 100644 --- a/include/linux/percpu-rwsem.h +++ b/include/linux/percpu-rwsem.h @@ -43,9 +43,10 @@ is_static struct percpu_rw_semaphore name = { \ #define DEFINE_STATIC_PERCPU_RWSEM(name) \ __DEFINE_PERCPU_RWSEM(name, static) -extern bool __percpu_down_read(struct percpu_rw_semaphore *, bool); +extern bool __percpu_down_read(struct percpu_rw_semaphore *, bool, bool); -static inline void percpu_down_read(struct percpu_rw_semaphore *sem) +static inline void percpu_down_read_internal(struct percpu_rw_semaphore *sem, + bool freezable) { might_sleep(); @@ -63,7 +64,7 @@ static inline void percpu_down_read(struct percpu_rw_semaphore *sem) if (likely(rcu_sync_is_idle(&sem->rss))) this_cpu_inc(*sem->read_count); else - __percpu_down_read(sem, false); /* Unconditional memory barrier */ + __percpu_down_read(sem, false, freezable); /* Unconditional memory barrier */ /* * The preempt_enable() prevents the compiler from * bleeding the critical section out. @@ -71,6 +72,17 @@ static inline void percpu_down_read(struct percpu_rw_semaphore *sem) preempt_enable(); } +static inline void percpu_down_read(struct percpu_rw_semaphore *sem) +{ + percpu_down_read_internal(sem, false); +} + +static inline void percpu_down_read_freezable(struct percpu_rw_semaphore *sem, + bool freeze) +{ + percpu_down_read_internal(sem, freeze); +} + static inline bool percpu_down_read_trylock(struct percpu_rw_semaphore *sem) { bool ret = true; @@ -82,7 +94,7 @@ static inline bool percpu_down_read_trylock(struct percpu_rw_semaphore *sem) if (likely(rcu_sync_is_idle(&sem->rss))) this_cpu_inc(*sem->read_count); else - ret = __percpu_down_read(sem, true); /* Unconditional memory barrier */ + ret = __percpu_down_read(sem, true, false); /* Unconditional memory barrier */ preempt_enable(); /* * The barrier() from preempt_enable() prevents the compiler from -- cgit v1.2.3