From: NeilBrown<neilb@xxxxxxx>
Date: Fri, 18 Sep 2009 15:55:09 +1000
Subject: [PATCH] md: support barrier requests on all personalities.
Previously barriers were only supported on RAID1. This is because
other levels requires synchronisation across all devices and so needed
a different approach.
Here is that approach.
When a barrier arrives, we send a zero-length barrier to every active
device. When that completes we submit the barrier request itself
(with the barrier flag cleared) and the submit a fresh load of
zero length barriers.
The barrier request itself is asynchronous, but any subsequent
request will block until the barrier completes.
The reason for clearing the barrier flag is that a barrier request is
allowed to fail. If we pass a non-empty barrier through a striping
raid level it is conceivable that part of it could succeed and part
could fail. That would be way to hard to deal with.
So if the first run of zero length barriers succeed, we assume all is
sufficiently well that we send the request and ignore errors in the
second run of barriers.
RAID5 needs extra care as write requests may not have been submitted
to the underlying devices yet. So we flush the stripe cache before
proceeding with the barrier.
Signed-off-by: NeilBrown<neilb@xxxxxxx>
---
drivers/md/linear.c | 2 +-
drivers/md/md.c | 111 +++++++++++++++++++++++++++++++++++++++++++++++-
drivers/md/md.h | 12 +++++
drivers/md/multipath.c | 2 +-
drivers/md/raid0.c | 2 +-
drivers/md/raid10.c | 2 +-
drivers/md/raid5.c | 8 +++-
7 files changed, 132 insertions(+), 7 deletions(-)
diff --git a/drivers/md/linear.c b/drivers/md/linear.c
index 53607c1..80504a8 100644
--- a/drivers/md/linear.c
+++ b/drivers/md/linear.c
@@ -292,7 +292,7 @@ static int linear_make_request (struct request_queue *q, struct bio *bio)
int cpu;
if (unlikely(bio_barrier(bio))) {
- bio_endio(bio, -EOPNOTSUPP);
+ md_barrier_request(mddev, bio);
return 0;
}
diff --git a/drivers/md/md.c b/drivers/md/md.c
index 8c41efe..820ae3b 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -217,12 +217,12 @@ static int md_make_request(struct request_queue *q, struct bio *bio)
return 0;
}
rcu_read_lock();
- if (mddev->suspended) {
+ if (mddev->suspended || mddev->barrier) {
DEFINE_WAIT(__wait);
for (;;) {
prepare_to_wait(&mddev->sb_wait,&__wait,
TASK_UNINTERRUPTIBLE);
- if (!mddev->suspended)
+ if (!mddev->suspended&& !mddev->barrier)
break;
rcu_read_unlock();
schedule();
@@ -264,10 +264,116 @@ static void mddev_resume(mddev_t *mddev)
int mddev_congested(mddev_t *mddev, int bits)
{
+ if (mddev->barrier)
+ return 1;
return mddev->suspended;
}
EXPORT_SYMBOL(mddev_congested);
+/*
+ * Generic barrier handling for md
+ */
+
+static void md_end_barrier(struct bio *bio, int err)
+{
+ mdk_rdev_t *rdev = bio->bi_private;
+ mddev_t *mddev = rdev->mddev;
+ if (err == -EOPNOTSUPP&& mddev->barrier != (void*)1)
+ set_bit(BIO_EOPNOTSUPP,&mddev->barrier->bi_flags);
+
+ rdev_dec_pending(rdev, mddev);
+
+ if (atomic_dec_and_test(&mddev->flush_pending)) {
+ if (mddev->barrier == (void*)1) {
+ mddev->barrier = NULL;
+ wake_up(&mddev->sb_wait);
+ } else
+ schedule_work(&mddev->barrier_work);
+ }
+ bio_put(bio);
+}
+
+static void md_submit_barrier(struct work_struct *ws)
+{
+ mddev_t *mddev = container_of(ws, mddev_t, barrier_work);
+ struct bio *bio = mddev->barrier;
+
+ atomic_set(&mddev->flush_pending, 1);
+
+ if (!test_bit(BIO_EOPNOTSUPP,&bio->bi_flags)) {
+ mdk_rdev_t *rdev;
+
+ bio->bi_rw&= ~(1<<BIO_RW_BARRIER);
+ if (mddev->pers->make_request(mddev->queue, bio))
+ generic_make_request(bio);
+ mddev->barrier = (void*)1;
+ rcu_read_lock();
+ list_for_each_entry_rcu(rdev,&mddev->disks, same_set)
+ if (rdev->raid_disk>= 0&&
+ !test_bit(Faulty,&rdev->flags)) {
+ /* Take two references, one is dropped
+ * when request finishes, one after
+ * we reclaim rcu_read_lock
+ */
+ struct bio *bi;
+ atomic_inc(&rdev->nr_pending);
+ atomic_inc(&rdev->nr_pending);
+ rcu_read_unlock();
+ bi = bio_alloc(GFP_KERNEL, 0);
+ bi->bi_end_io = md_end_barrier;
+ bi->bi_private = rdev;
+ bi->bi_bdev = rdev->bdev;
+ atomic_inc(&mddev->flush_pending);
+ submit_bio(WRITE_BARRIER, bi);
+ rcu_read_lock();
+ rdev_dec_pending(rdev, mddev);
+ }
+ rcu_read_unlock();
+ } else
+ bio_endio(bio, -EOPNOTSUPP);
+ if (atomic_dec_and_test(&mddev->flush_pending)) {
+ mddev->barrier = NULL;
+ wake_up(&mddev->sb_wait);
+ }
+}
+
+void md_barrier_request(mddev_t *mddev, struct bio *bio)
+{
+ mdk_rdev_t *rdev;
+
+ spin_lock_irq(&mddev->write_lock);
+ wait_event_lock_irq(mddev->sb_wait,
+ !mddev->barrier,
+ mddev->write_lock, /*nothing*/);
+ mddev->barrier = bio;
+ spin_unlock_irq(&mddev->write_lock);
+
+ atomic_set(&mddev->flush_pending, 1);
+ INIT_WORK(&mddev->barrier_work, md_submit_barrier);
+
+ rcu_read_lock();
+ list_for_each_entry_rcu(rdev,&mddev->disks, same_set)
+ if (rdev->raid_disk>= 0&&
+ !test_bit(Faulty,&rdev->flags)) {
+ struct bio *bi;
+
+ atomic_inc(&rdev->nr_pending);
+ atomic_inc(&rdev->nr_pending);
+ rcu_read_unlock();
+ bi = bio_alloc(GFP_KERNEL, 0);
+ bi->bi_end_io = md_end_barrier;
+ bi->bi_private = rdev;
+ bi->bi_bdev = rdev->bdev;
+ atomic_inc(&mddev->flush_pending);
+ submit_bio(WRITE_BARRIER, bi);
+ rcu_read_lock();
+ rdev_dec_pending(rdev, mddev);
+ }
+ rcu_read_unlock();
+ if (atomic_dec_and_test(&mddev->flush_pending))
+ schedule_work(&mddev->barrier_work);
+}
+EXPORT_SYMBOL(md_barrier_request);
static inline mddev_t *mddev_get(mddev_t *mddev)
{
@@ -374,6 +480,7 @@ static mddev_t * mddev_find(dev_t unit)
atomic_set(&new->openers, 0);
atomic_set(&new->active_io, 0);
spin_lock_init(&new->write_lock);
+ atomic_set(&new->flush_pending, 0);
init_waitqueue_head(&new->sb_wait);
init_waitqueue_head(&new->recovery_wait);
new->reshape_position = MaxSector;
diff --git a/drivers/md/md.h b/drivers/md/md.h
index 5de3902..57ccc6f 100644
--- a/drivers/md/md.h
+++ b/drivers/md/md.h
@@ -291,6 +291,17 @@ struct mddev_s
*/
struct list_head all_mddevs;
+
+ /* Generic barrier handling.
+ * If there is a pending barrier request, all other
+ * writes are blocked while the devices are flushed.
+ * The last to finish a flush schedules a worker to
+ * submit the barrier request (without the barrier flag),
+ * then submit more flush requests.
+ */
+ struct bio *barrier;
+ atomic_t flush_pending;
+ struct work_struct barrier_work;
};
@@ -431,6 +442,7 @@ extern void md_done_sync(mddev_t *mddev, int blocks, int ok);
extern void md_error(mddev_t *mddev, mdk_rdev_t *rdev);
extern int mddev_congested(mddev_t *mddev, int bits);
+extern void md_barrier_request(mddev_t *mddev, struct bio *bio);
extern void md_super_write(mddev_t *mddev, mdk_rdev_t *rdev,
sector_t sector, int size, struct page *page);
extern void md_super_wait(mddev_t *mddev);
diff --git a/drivers/md/multipath.c b/drivers/md/multipath.c
index ce4b4cd..f2bb20c 100644
--- a/drivers/md/multipath.c
+++ b/drivers/md/multipath.c
@@ -145,7 +145,7 @@ static int multipath_make_request (struct request_queue *q, struct bio * bio)
int cpu;
if (unlikely(bio_barrier(bio))) {
- bio_endio(bio, -EOPNOTSUPP);
+ md_barrier_request(mddev, bio);
return 0;
}
diff --git a/drivers/md/raid0.c b/drivers/md/raid0.c
index 08adcb0..87325c5 100644
--- a/drivers/md/raid0.c
+++ b/drivers/md/raid0.c
@@ -453,7 +453,7 @@ static int raid0_make_request(struct request_queue *q, struct bio *bio)
int cpu;
if (unlikely(bio_barrier(bio))) {
- bio_endio(bio, -EOPNOTSUPP);
+ md_barrier_request(mddev, bio);
return 0;
}
diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
index 3868880..113b672 100644
--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -804,7 +804,7 @@ static int make_request(struct request_queue *q, struct bio * bio)
mdk_rdev_t *blocked_rdev;
if (unlikely(bio_barrier(bio))) {
- bio_endio(bio, -EOPNOTSUPP);
+ md_barrier_request(mddev, bio);
return 0;
}
diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 584abea..7b6544e 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -3611,7 +3611,13 @@ static int make_request(struct request_queue *q, struct bio * bi)
int cpu, remaining;
if (unlikely(bio_barrier(bi))) {
- bio_endio(bi, -EOPNOTSUPP);
+ /* Drain all pending writes. We only really need
+ * to ensure they have been submitted, but this is
+ * easier.
+ */
+ mddev->pers->quiesce(mddev, 1);
+ mddev->pers->quiesce(mddev, 0);
+ md_barrier_request(mddev, bi);
return 0;
}
