From dd7382a2a7da91a475703810a87a80d6eae14645 Mon Sep 17 00:00:00 2001 From: Schspa Shi Date: Mon, 11 Apr 2022 23:55:41 +0800 Subject: [PATCH] btrfs: use non-bh spin_lock in zstd timer callback This is an optimization for fix fee13fe96529 ("btrfs: correct zstd workspace manager lock to use spin_lock_bh()") The critical region for wsm.lock is only accessed by the process context and the softirq context. Because in the soft interrupt, the critical section will not be preempted by the soft interrupt again, there is no need to call spin_lock_bh(&wsm.lock) to turn off the soft interrupt, spin_lock(&wsm.lock) is enough for this situation. Signed-off-by: Schspa Shi [ minor comment update ] Signed-off-by: David Sterba --- fs/btrfs/zstd.c | 14 +++++++++----- 1 file changed, 9 insertions(+), 5 deletions(-) diff --git a/fs/btrfs/zstd.c b/fs/btrfs/zstd.c index fc42dd0badd7..0fe31a6f6e68 100644 --- a/fs/btrfs/zstd.c +++ b/fs/btrfs/zstd.c @@ -93,22 +93,26 @@ static inline struct workspace *list_to_workspace(struct list_head *list) void zstd_free_workspace(struct list_head *ws); struct list_head *zstd_alloc_workspace(unsigned int level); -/* - * zstd_reclaim_timer_fn - reclaim timer + +/** + * Timer callback to free unused workspaces. + * * @t: timer * * This scans the lru_list and attempts to reclaim any workspace that hasn't * been used for ZSTD_BTRFS_RECLAIM_JIFFIES. + * + * The context is softirq and does not need the _bh locking primitives. */ static void zstd_reclaim_timer_fn(struct timer_list *timer) { unsigned long reclaim_threshold = jiffies - ZSTD_BTRFS_RECLAIM_JIFFIES; struct list_head *pos, *next; - spin_lock_bh(&wsm.lock); + spin_lock(&wsm.lock); if (list_empty(&wsm.lru_list)) { - spin_unlock_bh(&wsm.lock); + spin_unlock(&wsm.lock); return; } @@ -137,7 +141,7 @@ static void zstd_reclaim_timer_fn(struct timer_list *timer) if (!list_empty(&wsm.lru_list)) mod_timer(&wsm.timer, jiffies + ZSTD_BTRFS_RECLAIM_JIFFIES); - spin_unlock_bh(&wsm.lock); + spin_unlock(&wsm.lock); } /* -- 2.20.1