[Midnightbsd-cvs] src [9330] trunk/sys: When an NFS unmount occurs, once vflush() writes the last dirty

[laffer1 at midnightbsd.org]

Revision: 9330
          http://svnweb.midnightbsd.org/src/?rev=9330
Author:   laffer1
Date:     2017-03-04 10:59:04 -0500 (Sat, 04 Mar 2017)
Log Message:
-----------
When an NFS unmount occurs, once vflush() writes the last dirty
buffer for the last vnode on the mount back to the server, it
returns. At that point, the code continues with the unmount,
including freeing up the nfs specific part of the mount structure.
It is possible that an nfsiod thread will try to check for an
empty I/O queue in the nfs specific part of the mount structure
after it has been free'd by the unmount. This patch avoids this problem by
setting the iodmount entries for the mount back to NULL while holding the
mutex in the unmount and checking the appropriate entry is non-NULL after
acquiring the mutex in the nfsiod thread.

Obtained from: FreeBSD svn 250258

Modified Paths:
--------------
    trunk/sys/fs/nfsclient/nfs_clnfsiod.c
    trunk/sys/fs/nfsclient/nfs_clvfsops.c
    trunk/sys/nfsclient/nfs_nfsiod.c
    trunk/sys/nfsclient/nfs_vfsops.c

Modified: trunk/sys/fs/nfsclient/nfs_clnfsiod.c
===================================================================
--- trunk/sys/fs/nfsclient/nfs_clnfsiod.c	2017-03-04 15:58:07 UTC (rev 9329)
+++ trunk/sys/fs/nfsclient/nfs_clnfsiod.c	2017-03-04 15:59:04 UTC (rev 9330)
@@ -304,6 +304,14 @@
 		}
 		mtx_lock(&ncl_iod_mutex);
 		/*
+		 * Make sure the nmp hasn't been dismounted as soon as
+		 * ncl_doio() completes for the last buffer.
+		 */
+		nmp = ncl_iodmount[myiod];
+		if (nmp == NULL)
+			break;
+
+		/*
 		 * If there are more than one iod on this mount, then defect
 		 * so that the iods can be shared out fairly between the mounts
 		 */

Modified: trunk/sys/fs/nfsclient/nfs_clvfsops.c
===================================================================
--- trunk/sys/fs/nfsclient/nfs_clvfsops.c	2017-03-04 15:58:07 UTC (rev 9329)
+++ trunk/sys/fs/nfsclient/nfs_clvfsops.c	2017-03-04 15:59:04 UTC (rev 9330)
@@ -80,6 +80,9 @@
 extern struct timeval nfsboottime;
 extern struct nfsstats	newnfsstats;
 extern int nfsrv_useacl;
+extern enum nfsiod_state ncl_iodwant[NFS_MAXASYNCDAEMON];
+extern struct nfsmount *ncl_iodmount[NFS_MAXASYNCDAEMON];
+extern struct mtx ncl_iod_mutex;
 
 MALLOC_DEFINE(M_NEWNFSREQ, "newnfsclient_req", "New NFS request header");
 MALLOC_DEFINE(M_NEWNFSMNT, "newnfsmnt", "New NFS mount struct");
@@ -1410,7 +1413,7 @@
 {
 	struct thread *td;
 	struct nfsmount *nmp;
-	int error, flags = 0, trycnt = 0;
+	int error, flags = 0, i, trycnt = 0;
 
 	td = curthread;
 
@@ -1445,6 +1448,14 @@
 	 */
 	if ((mntflags & MNT_FORCE) == 0)
 		nfscl_umount(nmp, td);
+	/* Make sure no nfsiods are assigned to this mount. */
+	mtx_lock(&ncl_iod_mutex);
+	for (i = 0; i < NFS_MAXASYNCDAEMON; i++)
+		if (ncl_iodmount[i] == nmp) {
+			ncl_iodwant[i] = NFSIOD_AVAILABLE;
+			ncl_iodmount[i] = NULL;
+		}
+	mtx_unlock(&ncl_iod_mutex);
 	newnfs_disconnect(&nmp->nm_sockreq);
 	crfree(nmp->nm_sockreq.nr_cred);
 	FREE(nmp->nm_nam, M_SONAME);

Modified: trunk/sys/nfsclient/nfs_nfsiod.c
===================================================================
--- trunk/sys/nfsclient/nfs_nfsiod.c	2017-03-04 15:58:07 UTC (rev 9329)
+++ trunk/sys/nfsclient/nfs_nfsiod.c	2017-03-04 15:59:04 UTC (rev 9330)
@@ -308,6 +308,14 @@
 			mtx_unlock(&Giant);
 		mtx_lock(&nfs_iod_mtx);
 		/*
+		 * Make sure the nmp hasn't been dismounted as soon as
+		 * nfs_doio() completes for the last buffer.
+		 */
+		nmp = nfs_iodmount[myiod];
+		if (nmp == NULL)
+			break;
+
+		/*
 		 * If there are more than one iod on this mount, then defect
 		 * so that the iods can be shared out fairly between the mounts
 		 */

Modified: trunk/sys/nfsclient/nfs_vfsops.c
===================================================================
--- trunk/sys/nfsclient/nfs_vfsops.c	2017-03-04 15:58:07 UTC (rev 9329)
+++ trunk/sys/nfsclient/nfs_vfsops.c	2017-03-04 15:59:04 UTC (rev 9330)
@@ -1362,7 +1362,7 @@
 nfs_unmount(struct mount *mp, int mntflags)
 {
 	struct nfsmount *nmp;
-	int error, flags = 0;
+	int error, flags = 0, i;
 
 	if (mntflags & MNT_FORCE)
 		flags |= FORCECLOSE;
@@ -1387,6 +1387,14 @@
 	/*
 	 * We are now committed to the unmount.
 	 */
+	/* Make sure no nfsiods are assigned to this mount. */
+	mtx_lock(&nfs_iod_mtx);
+	for (i = 0; i < NFS_MAXASYNCDAEMON; i++)
+		if (nfs_iodmount[i] == nmp) {
+			nfs_iodwant[i] = NFSIOD_AVAILABLE;
+			nfs_iodmount[i] = NULL;
+		}
+	mtx_unlock(&nfs_iod_mtx);
 	nfs_disconnect(nmp);
 	free(nmp->nm_nam, M_SONAME);