diff options
Diffstat (limited to 'fs/xfs/xfs_drain.c')
| -rw-r--r-- | fs/xfs/xfs_drain.c | 26 |
1 files changed, 26 insertions, 0 deletions
diff --git a/fs/xfs/xfs_drain.c b/fs/xfs/xfs_drain.c index b431abdf0af1..005a66be44a2 100644 --- a/fs/xfs/xfs_drain.c +++ b/fs/xfs/xfs_drain.c @@ -12,6 +12,31 @@ #include "xfs_ag.h" #include "xfs_trace.h" +/* + * Use a static key here to reduce the overhead of xfs_drain_rele. If the + * compiler supports jump labels, the static branch will be replaced by a nop + * sled when there are no xfs_drain_wait callers. Online fsck is currently + * the only caller, so this is a reasonable tradeoff. + * + * Note: Patching the kernel code requires taking the cpu hotplug lock. Other + * parts of the kernel allocate memory with that lock held, which means that + * XFS callers cannot hold any locks that might be used by memory reclaim or + * writeback when calling the static_branch_{inc,dec} functions. + */ +static DEFINE_STATIC_KEY_FALSE(xfs_drain_waiter_gate); + +void +xfs_drain_wait_disable(void) +{ + static_branch_dec(&xfs_drain_waiter_gate); +} + +void +xfs_drain_wait_enable(void) +{ + static_branch_inc(&xfs_drain_waiter_gate); +} + void xfs_defer_drain_init( struct xfs_defer_drain *dr) @@ -46,6 +71,7 @@ static inline bool has_waiters(struct wait_queue_head *wq_head) static inline void xfs_defer_drain_rele(struct xfs_defer_drain *dr) { if (atomic_dec_and_test(&dr->dr_count) && + static_branch_unlikely(&xfs_drain_waiter_gate) && has_waiters(&dr->dr_waiters)) wake_up(&dr->dr_waiters); } |