[PATCH] md/raid1: use local list for pending write-bio in make_request()

Use local bio_list for gathering mirrored bios to reduce locking overhead.

Signed-off-by: Namhyung Kim
---
drivers/md/raid1.c | 10 +++++++---
1 files changed, 7 insertions(+), 3 deletions(-)

diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
index 5d096096f958..39e9f54038a8 100644
--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -707,6 +707,7 @@ static int make_request(mddev_t *mddev, struct bio * bio)
const unsigned long do_flush_fua = (bio->bi_rw & (REQ_FLUSH | REQ_FUA));
mdk_rdev_t *blocked_rdev;
int plugged;
+ struct bio_list write_list;

/*
* Register the new request and wait if the reconstruction
@@ -801,6 +802,7 @@ static int make_request(mddev_t *mddev, struct bio * bio)
plugged = mddev_check_plugged(mddev);

disks = conf->raid_disks;
+ bio_list_init(&write_list);
retry_write:
blocked_rdev = NULL;
rcu_read_lock();
@@ -894,10 +896,12 @@ static int make_request(mddev_t *mddev, struct bio * bio)
}

atomic_inc(&r1_bio->remaining);
- spin_lock_irqsave(&conf->device_lock, flags);
- bio_list_add(&conf->pending_bio_list, mbio);
- spin_unlock_irqrestore(&conf->device_lock, flags);
+ bio_list_add(&write_list, mbio);
}
+ spin_lock_irqsave(&conf->device_lock, flags);
+ bio_list_merge(&conf->pending_bio_list, &write_list);
+ spin_unlock_irqrestore(&conf->device_lock, flags);
+
r1_bio_write_done(r1_bio);

/* In case raid1d snuck in to freeze_array */
--
1.7.5.2

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