linux-kernel - [PATCH v2] btrfs: zstd: use spin

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Date:   Mon, 11 Apr 2022 23:55:41 +0800
From:   Schspa Shi <schspa@...il.com>
To:     dsterba@...e.cz
Cc:     clm@...com, dsterba@...e.com, josef@...icpanda.com,
        linux-btrfs@...r.kernel.org, linux-kernel@...r.kernel.org,
        schspa@...il.com, terrelln@...com
Subject: [PATCH v2] btrfs: zstd: use spin_lock in 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.

Changelog:
v1 -> v2:
	- Change the commit message to make it more readable.

[1] https://lore.kernel.org/all/20220408181523.92322-1-schspa@gmail.com/

Signed-off-by: Schspa Shi <schspa@...il.com>
---
 fs/btrfs/zstd.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/fs/btrfs/zstd.c b/fs/btrfs/zstd.c
index fc42dd0badd7..faa74306f0b7 100644
--- a/fs/btrfs/zstd.c
+++ b/fs/btrfs/zstd.c
@@ -105,10 +105,10 @@ 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 +137,7 @@ 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);
 }
 
 /*
-- 
2.24.3 (Apple Git-128)