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nfs4: fix potential race with rapid nfs_callback_up/down cycle 

If the nfsv4 callback thread is rapidly brought up and down, it's
possible that nfs_callback_svc might never get a chance to run. If
this happens, the cleanup at thread exit might never occur, throwing
the refcounting off and nfs_callback_info in an incorrect state.

Move the clean functions into nfs_callback_down. Also change the
nfs_callback_info struct to track the svc_rqst rather than svc_serv
since we need to know that to call svc_exit_thread.

Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
wifi-calibration
Jeff Layton 2008-06-11 10:03:11 -04:00 committed by Trond Myklebust
parent ee84dfc454
commit 5afc597c5f
1 changed files with 16 additions and 14 deletions
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30
fs/nfs/callback.c
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@ -27,7 +27,7 @@
struct nfs_callback_data {
unsigned int users;
struct svc_serv *serv;
struct svc_rqst *rqst;
struct task_struct *task;
};
@ -91,18 +91,15 @@ nfs_callback_svc(void *vrqstp)
svc_process(rqstp);
}
unlock_kernel();
nfs_callback_info.task = NULL;
svc_exit_thread(rqstp);
return 0;
}
/*
* Bring up the server process if it is not already up.
* Bring up the callback thread if it is not already up.
*/
int nfs_callback_up(void)
{
struct svc_serv *serv = NULL;
struct svc_rqst *rqstp;
int ret = 0;
mutex_lock(&nfs_callback_mutex);
@ -120,22 +117,23 @@ int nfs_callback_up(void)
nfs_callback_tcpport = ret;
dprintk("Callback port = 0x%x\n", nfs_callback_tcpport);
rqstp = svc_prepare_thread(serv, &serv->sv_pools[0]);
if (IS_ERR(rqstp)) {
ret = PTR_ERR(rqstp);
nfs_callback_info.rqst = svc_prepare_thread(serv, &serv->sv_pools[0]);
if (IS_ERR(nfs_callback_info.rqst)) {
ret = PTR_ERR(nfs_callback_info.rqst);
nfs_callback_info.rqst = NULL;
goto out_err;
}
svc_sock_update_bufs(serv);
nfs_callback_info.serv = serv;
nfs_callback_info.task = kthread_run(nfs_callback_svc, rqstp,
nfs_callback_info.task = kthread_run(nfs_callback_svc,
nfs_callback_info.rqst,
"nfsv4-svc");
if (IS_ERR(nfs_callback_info.task)) {
ret = PTR_ERR(nfs_callback_info.task);
nfs_callback_info.serv = NULL;
svc_exit_thread(nfs_callback_info.rqst);
nfs_callback_info.rqst = NULL;
nfs_callback_info.task = NULL;
svc_exit_thread(rqstp);
goto out_err;
}
out:
@ -157,14 +155,18 @@ out_err:
}
/*
* Kill the server process if it is not already down.
* Kill the callback thread if it's no longer being used.
*/
void nfs_callback_down(void)
{
mutex_lock(&nfs_callback_mutex);
nfs_callback_info.users--;
if (nfs_callback_info.users == 0 && nfs_callback_info.task != NULL)
if (nfs_callback_info.users == 0 && nfs_callback_info.task != NULL) {
kthread_stop(nfs_callback_info.task);
svc_exit_thread(nfs_callback_info.rqst);
nfs_callback_info.rqst = NULL;
nfs_callback_info.task = NULL;
}
mutex_unlock(&nfs_callback_mutex);
}