Do not fork nfsiod directly from the vop methods. This causes LORs between

vnode lock and several locks needed during fork, like fd lock.

Instead, schedule the task to be executed in the taskqueue context. We
still waiting for the fork to finish, but the context of the thread
executing the task does not make real LORs with our vnode lock.

Submitted by:	pluknet at gmail com
Reviewed by:	jhb
Tested by:	pho
MFC after:	3 weeks

1 files changed, 39 insertions, 2 deletions

diff --git a/sys/nfsclient/nfs_nfsiod.c b/sys/nfsclient/nfs_nfsiod.c
index d192848..5e2fbcc 100644
--- a/sys/nfsclient/nfs_nfsiod.c
+++ b/sys/nfsclient/nfs_nfsiod.c
@@ -59,6 +59,7 @@ __FBSDID("$FreeBSD$");
 #include <sys/fcntl.h>
 #include <sys/lockf.h>
 #include <sys/mutex.h>
+#include <sys/taskqueue.h>
 
 #include <netinet/in.h>
 #include <netinet/tcp.h>
@@ -75,6 +76,16 @@ static MALLOC_DEFINE(M_NFSSVC, "nfsclient_srvsock", "Nfs server structure");
 
 static void	nfssvc_iod(void *);
 
+struct nfsiod_str {
+	STAILQ_ENTRY(nfsiod_str) ni_links;
+	int *ni_inst;
+	int ni_iod;
+	int ni_error;
+	int ni_done;
+};
+static STAILQ_HEAD(, nfsiod_str) nfsiodhead =
+    STAILQ_HEAD_INITIALIZER(nfsiodhead);
+
 static int nfs_asyncdaemon[NFS_MAXASYNCDAEMON];
 
 SYSCTL_DECL(_vfs_nfs);
@@ -159,11 +170,30 @@ SYSCTL_PROC(_vfs_nfs, OID_AUTO, iodmax, CTLTYPE_UINT | CTLFLAG_RW, 0,
     sizeof (nfs_iodmax), sysctl_iodmax, "IU",
     "Max number of nfsiod kthreads");
 
+void
+nfs_nfsiodnew_tq(__unused void *arg, int pending)
+{
+	struct nfsiod_str *nip;
+
+	mtx_lock(&nfs_iod_mtx);
+	while ((nip = STAILQ_FIRST(&nfsiodhead)) != NULL) {
+		STAILQ_REMOVE_HEAD(&nfsiodhead, ni_links);
+		mtx_unlock(&nfs_iod_mtx);
+		nip->ni_error = kproc_create(nfssvc_iod, nip->ni_inst, NULL,
+		    RFHIGHPID, 0, "nfsiod %d", nip->ni_iod);
+		nip->ni_done = 1;
+		mtx_lock(&nfs_iod_mtx);
+		wakeup(nip);
+	}
+	mtx_unlock(&nfs_iod_mtx);
+}
+
 int
 nfs_nfsiodnew(int set_iodwant)
 {
 	int error, i;
 	int newiod;
+	struct nfsiod_str *nip;
 
 	if (nfs_numasync >= nfs_iodmax)
 		return (-1);
@@ -179,9 +209,16 @@ nfs_nfsiodnew(int set_iodwant)
 	if (set_iodwant > 0)
 		nfs_iodwant[i] = NFSIOD_CREATED_FOR_NFS_ASYNCIO;
 	mtx_unlock(&nfs_iod_mtx);
-	error = kproc_create(nfssvc_iod, nfs_asyncdaemon + i, NULL, RFHIGHPID,
-	    0, "nfsiod %d", newiod);
+	nip = malloc(sizeof(*nip), M_TEMP, M_WAITOK | M_ZERO);
+	nip->ni_inst = nfs_asyncdaemon + i;
+	nip->ni_iod = newiod;
 	mtx_lock(&nfs_iod_mtx);
+	STAILQ_INSERT_TAIL(&nfsiodhead, nip, ni_links);
+	taskqueue_enqueue(taskqueue_thread, &nfs_nfsiodnew_task);
+	while (!nip->ni_done)
+		mtx_sleep(nip, &nfs_iod_mtx, 0, "niwt", 0);
+	error = nip->ni_error;
+	free(nip, M_TEMP);
 	if (error) {
 		if (set_iodwant > 0)
 			nfs_iodwant[i] = NFSIOD_NOT_AVAILABLE;