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SUNRPC: Fix potential races in xprt_lock_write_next()

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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>
This commit is contained in:
Trond Myklebust 2012-01-17 22:57:37 -05:00
parent 2aeb98f498
commit 961a828df6
6 changed files with 79 additions and 46 deletions
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1
fs/nfs/nfs4_fs.h
View File

@ -222,6 +222,7 @@ static inline struct nfs4_session *nfs4_get_session(const struct nfs_server *ser
return server->nfs_client->cl_session;
}
extern bool nfs4_set_task_privileged(struct rpc_task *task, void *dummy);
extern int nfs4_setup_sequence(const struct nfs_server *server,
struct nfs4_sequence_args *args, struct nfs4_sequence_res *res,
struct rpc_task *task);

13
fs/nfs/nfs4proc.c
View File

@ -385,17 +385,20 @@ nfs4_free_slot(struct nfs4_slot_table *tbl, u8 free_slotid)
free_slotid, tbl->highest_used_slotid);
}
bool nfs4_set_task_privileged(struct rpc_task *task, void *dummy)
{
rpc_task_set_priority(task, RPC_PRIORITY_PRIVILEGED);
return true;
}
/*
* Signal state manager thread if session fore channel is drained
*/
static void nfs4_check_drain_fc_complete(struct nfs4_session *ses)
{
struct rpc_task *task;
if (!test_bit(NFS4_SESSION_DRAINING, &ses->session_state)) {
task = rpc_wake_up_next(&ses->fc_slot_table.slot_tbl_waitq);
if (task)
rpc_task_set_priority(task, RPC_PRIORITY_PRIVILEGED);
rpc_wake_up_first(&ses->fc_slot_table.slot_tbl_waitq,
nfs4_set_task_privileged, NULL);
return;
}

17
fs/nfs/nfs4state.c
View File

@ -190,23 +190,22 @@ static int nfs41_setup_state_renewal(struct nfs_client *clp)
static void nfs4_end_drain_session(struct nfs_client *clp)
{
struct nfs4_session *ses = clp->cl_session;
struct nfs4_slot_table *tbl;
int max_slots;
if (ses == NULL)
return;
tbl = &ses->fc_slot_table;
if (test_and_clear_bit(NFS4_SESSION_DRAINING, &ses->session_state)) {
spin_lock(&ses->fc_slot_table.slot_tbl_lock);
max_slots = ses->fc_slot_table.max_slots;
spin_lock(&tbl->slot_tbl_lock);
max_slots = tbl->max_slots;
while (max_slots--) {
struct rpc_task *task;
task = rpc_wake_up_next(&ses->fc_slot_table.
slot_tbl_waitq);
if (!task)
if (rpc_wake_up_first(&tbl->slot_tbl_waitq,
nfs4_set_task_privileged,
NULL) == NULL)
break;
rpc_task_set_priority(task, RPC_PRIORITY_PRIVILEGED);
}
spin_unlock(&ses->fc_slot_table.slot_tbl_lock);
spin_unlock(&tbl->slot_tbl_lock);
}
}

3
include/linux/sunrpc/sched.h
View File

@ -235,6 +235,9 @@ void rpc_wake_up_queued_task(struct rpc_wait_queue *,
struct rpc_task *);
void rpc_wake_up(struct rpc_wait_queue *);
struct rpc_task *rpc_wake_up_next(struct rpc_wait_queue *);
struct rpc_task *rpc_wake_up_first(struct rpc_wait_queue *,
bool (*)(struct rpc_task *, void *),
void *);
void rpc_wake_up_status(struct rpc_wait_queue *, int);
int rpc_queue_empty(struct rpc_wait_queue *);
void rpc_delay(struct rpc_task *, unsigned long);

42
net/sunrpc/sched.c
View File

@ -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);
/**

49
net/sunrpc/xprt.c
View File

@ -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);
}