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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>
This commit is contained in:
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
View File

@ -27,7 +27,7 @@
struct nfs_callback_data { struct nfs_callback_data {
unsigned int users; unsigned int users;
struct svc_serv *serv; struct svc_rqst *rqst;
struct task_struct *task; struct task_struct *task;
}; };
@ -91,18 +91,15 @@ nfs_callback_svc(void *vrqstp)
svc_process(rqstp); svc_process(rqstp);
} }
unlock_kernel(); unlock_kernel();
nfs_callback_info.task = NULL;
svc_exit_thread(rqstp);
return 0; 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) int nfs_callback_up(void)
{ {
struct svc_serv *serv = NULL; struct svc_serv *serv = NULL;
struct svc_rqst *rqstp;
int ret = 0; int ret = 0;
mutex_lock(&nfs_callback_mutex); mutex_lock(&nfs_callback_mutex);
@ -120,22 +117,23 @@ int nfs_callback_up(void)
nfs_callback_tcpport = ret; nfs_callback_tcpport = ret;
dprintk("Callback port = 0x%x\n", nfs_callback_tcpport); dprintk("Callback port = 0x%x\n", nfs_callback_tcpport);
rqstp = svc_prepare_thread(serv, &serv->sv_pools[0]); nfs_callback_info.rqst = svc_prepare_thread(serv, &serv->sv_pools[0]);
if (IS_ERR(rqstp)) { if (IS_ERR(nfs_callback_info.rqst)) {
ret = PTR_ERR(rqstp); ret = PTR_ERR(nfs_callback_info.rqst);
nfs_callback_info.rqst = NULL;
goto out_err; goto out_err;
} }
svc_sock_update_bufs(serv); 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"); "nfsv4-svc");
if (IS_ERR(nfs_callback_info.task)) { if (IS_ERR(nfs_callback_info.task)) {
ret = PTR_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; nfs_callback_info.task = NULL;
svc_exit_thread(rqstp);
goto out_err; goto out_err;
} }
out: 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) void nfs_callback_down(void)
{ {
mutex_lock(&nfs_callback_mutex); mutex_lock(&nfs_callback_mutex);
nfs_callback_info.users--; 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); 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); mutex_unlock(&nfs_callback_mutex);
} }