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author | Trond Myklebust <Trond.Myklebust@netapp.com> | 2012-01-18 04:57:37 +0100 |
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committer | Trond Myklebust <Trond.Myklebust@netapp.com> | 2012-02-01 01:28:08 +0100 |
commit | 961a828df64979d2a9faeeeee043391670a193b9 (patch) | |
tree | 4b7ddaf1a19c589e3c8ec96b6c732faa507f2899 /net/sunrpc | |
parent | NFS: Ensure that mmapped pages remain stable during writeback (diff) | |
download | linux-961a828df64979d2a9faeeeee043391670a193b9.tar.xz linux-961a828df64979d2a9faeeeee043391670a193b9.zip |
SUNRPC: Fix potential races in xprt_lock_write_next()
We have to ensure that the wake up from the waitqueue and the assignment
of xprt->snd_task are atomic. We can do this by assigning the snd_task
while under the waitqueue spinlock.
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Diffstat (limited to 'net/sunrpc')
-rw-r--r-- | net/sunrpc/sched.c | 42 | ||||
-rw-r--r-- | net/sunrpc/xprt.c | 49 |
2 files changed, 59 insertions, 32 deletions
diff --git a/net/sunrpc/sched.c b/net/sunrpc/sched.c index 3341d8962786..f982dfe53993 100644 --- a/net/sunrpc/sched.c +++ b/net/sunrpc/sched.c @@ -422,7 +422,7 @@ EXPORT_SYMBOL_GPL(rpc_wake_up_queued_task); /* * Wake up the next task on a priority queue. */ -static struct rpc_task * __rpc_wake_up_next_priority(struct rpc_wait_queue *queue) +static struct rpc_task *__rpc_find_next_queued_priority(struct rpc_wait_queue *queue) { struct list_head *q; struct rpc_task *task; @@ -467,30 +467,54 @@ new_queue: new_owner: rpc_set_waitqueue_owner(queue, task->tk_owner); out: - rpc_wake_up_task_queue_locked(queue, task); return task; } +static struct rpc_task *__rpc_find_next_queued(struct rpc_wait_queue *queue) +{ + if (RPC_IS_PRIORITY(queue)) + return __rpc_find_next_queued_priority(queue); + if (!list_empty(&queue->tasks[0])) + return list_first_entry(&queue->tasks[0], struct rpc_task, u.tk_wait.list); + return NULL; +} + /* - * Wake up the next task on the wait queue. + * Wake up the first task on the wait queue. */ -struct rpc_task * rpc_wake_up_next(struct rpc_wait_queue *queue) +struct rpc_task *rpc_wake_up_first(struct rpc_wait_queue *queue, + bool (*func)(struct rpc_task *, void *), void *data) { struct rpc_task *task = NULL; - dprintk("RPC: wake_up_next(%p \"%s\")\n", + dprintk("RPC: wake_up_first(%p \"%s\")\n", queue, rpc_qname(queue)); spin_lock_bh(&queue->lock); - if (RPC_IS_PRIORITY(queue)) - task = __rpc_wake_up_next_priority(queue); - else { - task_for_first(task, &queue->tasks[0]) + task = __rpc_find_next_queued(queue); + if (task != NULL) { + if (func(task, data)) rpc_wake_up_task_queue_locked(queue, task); + else + task = NULL; } spin_unlock_bh(&queue->lock); return task; } +EXPORT_SYMBOL_GPL(rpc_wake_up_first); + +static bool rpc_wake_up_next_func(struct rpc_task *task, void *data) +{ + return true; +} + +/* + * Wake up the next task on the wait queue. +*/ +struct rpc_task *rpc_wake_up_next(struct rpc_wait_queue *queue) +{ + return rpc_wake_up_first(queue, rpc_wake_up_next_func, NULL); +} EXPORT_SYMBOL_GPL(rpc_wake_up_next); /** diff --git a/net/sunrpc/xprt.c b/net/sunrpc/xprt.c index c64c0ef519b5..839f6ef2326b 100644 --- a/net/sunrpc/xprt.c +++ b/net/sunrpc/xprt.c @@ -292,54 +292,57 @@ static inline int xprt_lock_write(struct rpc_xprt *xprt, struct rpc_task *task) return retval; } -static void __xprt_lock_write_next(struct rpc_xprt *xprt) +static bool __xprt_lock_write_func(struct rpc_task *task, void *data) { - struct rpc_task *task; + struct rpc_xprt *xprt = data; struct rpc_rqst *req; - if (test_and_set_bit(XPRT_LOCKED, &xprt->state)) - return; - - task = rpc_wake_up_next(&xprt->sending); - if (task == NULL) - goto out_unlock; - req = task->tk_rqstp; xprt->snd_task = task; if (req) { req->rq_bytes_sent = 0; req->rq_ntrans++; } - return; + return true; +} -out_unlock: +static void __xprt_lock_write_next(struct rpc_xprt *xprt) +{ + if (test_and_set_bit(XPRT_LOCKED, &xprt->state)) + return; + + if (rpc_wake_up_first(&xprt->sending, __xprt_lock_write_func, xprt)) + return; xprt_clear_locked(xprt); } -static void __xprt_lock_write_next_cong(struct rpc_xprt *xprt) +static bool __xprt_lock_write_cong_func(struct rpc_task *task, void *data) { - struct rpc_task *task; + struct rpc_xprt *xprt = data; struct rpc_rqst *req; - if (test_and_set_bit(XPRT_LOCKED, &xprt->state)) - return; - if (RPCXPRT_CONGESTED(xprt)) - goto out_unlock; - task = rpc_wake_up_next(&xprt->sending); - if (task == NULL) - goto out_unlock; - req = task->tk_rqstp; if (req == NULL) { xprt->snd_task = task; - return; + return true; } if (__xprt_get_cong(xprt, task)) { xprt->snd_task = task; req->rq_bytes_sent = 0; req->rq_ntrans++; - return; + return true; } + return false; +} + +static void __xprt_lock_write_next_cong(struct rpc_xprt *xprt) +{ + if (test_and_set_bit(XPRT_LOCKED, &xprt->state)) + return; + if (RPCXPRT_CONGESTED(xprt)) + goto out_unlock; + if (rpc_wake_up_first(&xprt->sending, __xprt_lock_write_cong_func, xprt)) + return; out_unlock: xprt_clear_locked(xprt); } |