svn commit: r249630 - in head/sys: fs/nfsclient nfsclient

[Rick Macklem]

Author: rmacklem
Date: Thu Apr 18 23:20:16 2013
New Revision: 249630
URL: http://svnweb.freebsd.org/changeset/base/249630

Log:
  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.
  
  Reported and tested by:	pho
  Reviewed by:	kib
  MFC after:	2 weeks

Modified:
  head/sys/fs/nfsclient/nfs_clnfsiod.c
  head/sys/fs/nfsclient/nfs_clvfsops.c
  head/sys/nfsclient/nfs_nfsiod.c
  head/sys/nfsclient/nfs_vfsops.c

Modified: head/sys/fs/nfsclient/nfs_clnfsiod.c
==============================================================================
--- head/sys/fs/nfsclient/nfs_clnfsiod.c	Thu Apr 18 22:54:41 2013	(r249629)
+++ head/sys/fs/nfsclient/nfs_clnfsiod.c	Thu Apr 18 23:20:16 2013	(r249630)
@@ -304,6 +304,14 @@ nfssvc_iod(void *instance)
 		}
 		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: head/sys/fs/nfsclient/nfs_clvfsops.c
==============================================================================
--- head/sys/fs/nfsclient/nfs_clvfsops.c	Thu Apr 18 22:54:41 2013	(r249629)
+++ head/sys/fs/nfsclient/nfs_clvfsops.c	Thu Apr 18 23:20:16 2013	(r249630)
@@ -81,6 +81,9 @@ extern struct timeval nfsboottime;
 extern struct nfsstats	newnfsstats;
 extern int nfsrv_useacl;
 extern int nfscl_debuglevel;
+extern enum nfsiod_state ncl_iodwant[NFS_MAXASYNCDAEMON];
+extern struct nfsmount *ncl_iodmount[NFS_MAXASYNCDAEMON];
+extern struct mtx ncl_iod_mutex;
 NFSCLSTATEMUTEX;
 
 MALLOC_DEFINE(M_NEWNFSREQ, "newnfsclient_req", "New NFS request header");
@@ -1472,7 +1475,7 @@ nfs_unmount(struct mount *mp, int mntfla
 {
 	struct thread *td;
 	struct nfsmount *nmp;
-	int error, flags = 0, trycnt = 0;
+	int error, flags = 0, i, trycnt = 0;
 	struct nfsclds *dsp, *tdsp;
 
 	td = curthread;
@@ -1508,6 +1511,14 @@ nfs_unmount(struct mount *mp, int mntfla
 	 */
 	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: head/sys/nfsclient/nfs_nfsiod.c
==============================================================================
--- head/sys/nfsclient/nfs_nfsiod.c	Thu Apr 18 22:54:41 2013	(r249629)
+++ head/sys/nfsclient/nfs_nfsiod.c	Thu Apr 18 23:20:16 2013	(r249630)
@@ -308,6 +308,14 @@ nfssvc_iod(void *instance)
 			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: head/sys/nfsclient/nfs_vfsops.c
==============================================================================
--- head/sys/nfsclient/nfs_vfsops.c	Thu Apr 18 22:54:41 2013	(r249629)
+++ head/sys/nfsclient/nfs_vfsops.c	Thu Apr 18 23:20:16 2013	(r249630)
@@ -1362,7 +1362,7 @@ static int
 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 @@ nfs_unmount(struct mount *mp, int mntfla
 	/*
 	 * 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);