linux-kernel - [PATCH AUTOSEL for 4.4 002/167] md/raid5: make use of spin_lock_irq over local_irq_disable + spin

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Date:   Mon, 19 Mar 2018 16:05:21 +0000
From:   Sasha Levin <Alexander.Levin@...rosoft.com>
To:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>
CC:     Julia Cartwright <julia@...com>, Shaohua Li <shli@...com>,
        Sasha Levin <Alexander.Levin@...rosoft.com>
Subject: [PATCH AUTOSEL for 4.4 002/167] md/raid5: make use of spin_lock_irq
 over local_irq_disable + spin_lock

From: Julia Cartwright <julia@...com>

[ Upstream commit 3d05f3aed5d721c2c77d20288c29ab26c6193ed5 ]

On mainline, there is no functional difference, just less code, and
symmetric lock/unlock paths.

On PREEMPT_RT builds, this fixes the following warning, seen by
Alexander GQ Gerasiov, due to the sleeping nature of spinlocks.

   BUG: sleeping function called from invalid context at kernel/locking/rtmutex.c:993
   in_atomic(): 0, irqs_disabled(): 1, pid: 58, name: kworker/u12:1
   CPU: 5 PID: 58 Comm: kworker/u12:1 Tainted: G        W       4.9.20-rt16-stand6-686 #1
   Hardware name: Supermicro SYS-5027R-WRF/X9SRW-F, BIOS 3.2a 10/28/2015
   Workqueue: writeback wb_workfn (flush-253:0)
   Call Trace:
    dump_stack+0x47/0x68
    ? migrate_enable+0x4a/0xf0
    ___might_sleep+0x101/0x180
    rt_spin_lock+0x17/0x40
    add_stripe_bio+0x4e3/0x6c0 [raid456]
    ? preempt_count_add+0x42/0xb0
    raid5_make_request+0x737/0xdd0 [raid456]

Reported-by: Alexander GQ Gerasiov <gq@...lab-i.ru>
Tested-by: Alexander GQ Gerasiov <gq@...lab-i.ru>
Signed-off-by: Julia Cartwright <julia@...com>
Signed-off-by: Shaohua Li <shli@...com>
Signed-off-by: Sasha Levin <alexander.levin@...rosoft.com>
---
 drivers/md/raid5.c | 17 +++++++----------
 1 file changed, 7 insertions(+), 10 deletions(-)

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 86ab6d14d782..0feffd3e29e7 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -110,8 +110,7 @@ static inline void unlock_device_hash_lock(struct r5conf *conf, int hash)
 static inline void lock_all_device_hash_locks_irq(struct r5conf *conf)
 {
 	int i;
-	local_irq_disable();
-	spin_lock(conf->hash_locks);
+	spin_lock_irq(conf->hash_locks);
 	for (i = 1; i < NR_STRIPE_HASH_LOCKS; i++)
 		spin_lock_nest_lock(conf->hash_locks + i, conf->hash_locks);
 	spin_lock(&conf->device_lock);
@@ -121,9 +120,9 @@ static inline void unlock_all_device_hash_locks_irq(struct r5conf *conf)
 {
 	int i;
 	spin_unlock(&conf->device_lock);
-	for (i = NR_STRIPE_HASH_LOCKS; i; i--)
-		spin_unlock(conf->hash_locks + i - 1);
-	local_irq_enable();
+	for (i = NR_STRIPE_HASH_LOCKS - 1; i; i--)
+		spin_unlock(conf->hash_locks + i);
+	spin_unlock_irq(conf->hash_locks);
 }
 
 /* bio's attached to a stripe+device for I/O are linked together in bi_sector
@@ -726,12 +725,11 @@ static bool is_full_stripe_write(struct stripe_head *sh)
 
 static void lock_two_stripes(struct stripe_head *sh1, struct stripe_head *sh2)
 {
-	local_irq_disable();
 	if (sh1 > sh2) {
-		spin_lock(&sh2->stripe_lock);
+		spin_lock_irq(&sh2->stripe_lock);
 		spin_lock_nested(&sh1->stripe_lock, 1);
 	} else {
-		spin_lock(&sh1->stripe_lock);
+		spin_lock_irq(&sh1->stripe_lock);
 		spin_lock_nested(&sh2->stripe_lock, 1);
 	}
 }
@@ -739,8 +737,7 @@ static void lock_two_stripes(struct stripe_head *sh1, struct stripe_head *sh2)
 static void unlock_two_stripes(struct stripe_head *sh1, struct stripe_head *sh2)
 {
 	spin_unlock(&sh1->stripe_lock);
-	spin_unlock(&sh2->stripe_lock);
-	local_irq_enable();
+	spin_unlock_irq(&sh2->stripe_lock);
 }
 
 /* Only freshly new full stripe normal write stripe can be added to a batch list */
-- 
2.14.1