Miao Xie
2010-Jul-29 08:30 UTC
[PATCH 5/7] btrfs: fix bad exception handling of __btrfs_start_workers()
If we stop all of the kthread when creating a new kthread fails, the btrfs
will hangup because there is no kthread to deal with the requests submited
by the btrfs.
And the best way to handle kthread-creating failure is "don''t do
anything",
because there are other kthreads in the kthread pool to deal with the
requests.
Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
---
fs/btrfs/async-thread.c | 51 +++++++++++++++++++++++++++++++++++-----------
1 files changed, 39 insertions(+), 12 deletions(-)
diff --git a/fs/btrfs/async-thread.c b/fs/btrfs/async-thread.c
index eb3ec2d..49d25e6 100644
--- a/fs/btrfs/async-thread.c
+++ b/fs/btrfs/async-thread.c
@@ -157,27 +157,45 @@ static void check_pending_worker_creates(struct
btrfs_worker_thread *worker)
{
struct btrfs_workers *workers = worker->workers;
unsigned long flags;
+ int ret;
rmb();
if (!workers->atomic_start_pending)
return;
- spin_lock_irqsave(&workers->lock, flags);
+ spin_lock_irqsave(&worker->lock, flags);
+ spin_lock(&workers->lock);
if (!workers->atomic_start_pending)
goto out;
- workers->atomic_start_pending = 0;
- if (workers->num_workers + workers->num_workers_starting >-
workers->max_workers)
+ /*
+ * If the worker is going to be idle, or the number of the workers is
+ * greater than the max number, we needn''t create any worker.
+ */
+ if (atomic_read(&worker->num_pending) < workers->idle_thresh / 2
||
+ workers->num_workers + workers->num_workers_starting >+
workers->max_workers) {
+ workers->atomic_start_pending = 0;
goto out;
+ }
- workers->num_workers_starting += 1;
- spin_unlock_irqrestore(&workers->lock, flags);
- start_new_worker(workers);
+ workers->atomic_start_pending = 0;
+ workers->num_workers_starting++;
+ spin_unlock(&workers->lock);
+ spin_unlock_irqrestore(&worker->lock, flags);
+
+ ret = start_new_worker(workers);
+ if (ret) {
+ spin_lock_irqsave(&workers->lock, flags);
+ workers->num_workers_starting--;
+ workers->atomic_start_pending = 1;
+ spin_unlock_irqrestore(&workers->lock, flags);
+ }
return;
out:
- spin_unlock_irqrestore(&workers->lock, flags);
+ spin_unlock(&workers->lock);
+ spin_unlock_irqrestore(&worker->lock, flags);
}
static noinline int run_ordered_completions(struct btrfs_workers *workers,
@@ -489,7 +507,7 @@ static int __btrfs_start_workers(struct btrfs_workers
*workers,
worker->workers = workers;
worker->task = kthread_run(worker_loop, worker,
"btrfs-%s-%d", workers->name,
- workers->num_workers + i);
+ workers->num_workers);
if (IS_ERR(worker->task)) {
ret = PTR_ERR(worker->task);
kfree(worker);
@@ -505,7 +523,12 @@ static int __btrfs_start_workers(struct btrfs_workers
*workers,
}
return 0;
fail:
- btrfs_stop_workers(workers);
+ spin_lock_irq(&workers->lock);
+ if (workers->atomic_worker_start && workers->num_workers)
+ workers->atomic_start_pending = 1;
+ workers->num_workers_starting -= num_workers - i;
+ WARN_ON(workers->num_workers_starting < 0);
+ spin_unlock_irq(&workers->lock);
return ret;
}
@@ -571,6 +594,7 @@ static struct btrfs_worker_thread *find_worker(struct
btrfs_workers *workers)
struct btrfs_worker_thread *worker;
unsigned long flags;
struct list_head *fallback;
+ int ret;
again:
spin_lock_irqsave(&workers->lock, flags);
@@ -587,8 +611,11 @@ again:
workers->num_workers_starting++;
spin_unlock_irqrestore(&workers->lock, flags);
/* we''re below the limit, start another worker */
- __btrfs_start_workers(workers, 1);
- goto again;
+ ret = __btrfs_start_workers(workers, 1);
+ if (ret)
+ goto fallback;
+ else
+ goto again;
}
}
goto found;
--
1.7.0.1