[PATCH AUTOSEL for 4.4 002/167] md/raid5: make use of spin_lock_irq over local_irq_disable + spin_lock

Sasha Levin
2018-03-19T17:38:53Z

From: Julia Cartwright <julia@ni.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@redlab-i.ru>
Tested-by: Alexander GQ Gerasiov <gq@redlab-i.ru>
Signed-off-by: Julia Cartwright <julia@ni.com>
Signed-off-by: Shaohua Li <shli@fb.com>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.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