LX-1396 umount failed (part deux)

https://github.com/delphix/zfs/pull/36/files/f75f7d2c9082d5e6d9e6a5c3670bc81fe03d87bb

Signed-off-by: Bryant G. Ly <bly@catalogicsoftware.com>

cmd/zfs/zfs_main.c

@@ -596,6 +596,20 @@ parseprop(nvlist_t *props, char *propname)
 		    "specified multiple times\n"), propname);
 		return (B_FALSE);
 	}
+
+	/*
+	 * If we are setting the sharenfs property, lock the sharetab to
+	 * ensure concurrent writers don't update the file simultaneously.
+	 * The sharetab will remain locked until the process exits.
+	 */
+	if (strcmp(propname, zfs_prop_to_name(ZFS_PROP_SHARENFS)) == 0) {
+		if (sharetab_lock() != 0) {
+			(void) fprintf(stderr, gettext("unable to set "
+			    "property: %s\n"), strerror(errno));
+			exit(1);
+		}
+	}
+
 	if (nvlist_add_string(props, propname, propval) != 0)
 		nomem();
 	return (B_TRUE);

cmd/zpool/zpool_main.c

@@ -66,6 +66,7 @@
 
 #include <libzfs.h>
 #include <libzutil.h>
+#include <libshare.h>
 
 #include "zpool_util.h"
 #include "zfs_comutil.h"
@@ -1614,12 +1615,15 @@ zpool_do_destroy(int argc, char **argv)
 		return (1);
 	}
 
+	verify(sharetab_lock() == 0);
 	if (zpool_disable_datasets(zhp, force) != 0) {
 		(void) fprintf(stderr, gettext("could not destroy '%s': "
 		    "could not unmount datasets\n"), zpool_get_name(zhp));
 		zpool_close(zhp);
+		verify(sharetab_unlock() == 0);
 		return (1);
 	}
+	verify(sharetab_unlock() == 0);
 
 	/* The history must be logged as part of the export */
 	log_history = B_FALSE;
@@ -1644,8 +1648,12 @@ zpool_export_one(zpool_handle_t *zhp, void *data)
 {
 	export_cbdata_t *cb = data;
 
-	if (zpool_disable_datasets(zhp, cb->force || cb->hardforce) != 0)
+	verify(sharetab_lock() == 0);
+	if (zpool_disable_datasets(zhp, cb->force || cb->hardforce) != 0) {
+		verify(sharetab_unlock() == 0);
 		return (1);
+	}
+	verify(sharetab_unlock() == 0);
 
 	/* The history must be logged as part of the export */
 	log_history = B_FALSE;
@@ -2827,12 +2835,15 @@ do_import(nvlist_t *config, const char *newname, const char *mntopts,
 			ret = 1;
 	}
 
+	verify(sharetab_lock() == 0);
 	if (zpool_get_state(zhp) != POOL_STATE_UNAVAIL &&
 	    !(flags & ZFS_IMPORT_ONLY) &&
 	    zpool_enable_datasets(zhp, mntopts, 0) != 0) {
 		zpool_close(zhp);
+		verify(sharetab_unlock() == 0);
 		return (1);
 	}
+	verify(sharetab_unlock() == 0);
 
 	zpool_close(zhp);
 	return (ret);

lib/libshare/libshare.c

@@ -173,18 +173,18 @@ sharetab_lock(void)
 {
 	struct flock lock;
 
-	assert(sharetab_fd == -1);
+	verify(sharetab_fd == -1);
 
 	if (mkdir("/etc/dfs", 0755) < 0 && errno != EEXIST) {
 		perror("sharetab_lock: failed to create /etc/dfs");
-		return (-1);
+		return (errno);
 	}
 
 	sharetab_fd = open(ZFS_SHARETAB_LOCK, (O_RDWR | O_CREAT), 0600);
 
 	if (sharetab_fd < 0) {
 		perror("sharetab_lock: failed to open");
-		return (-1);
+		return (errno);
 	}
 
 	lock.l_type = F_WRLCK;
@@ -193,7 +193,7 @@ sharetab_lock(void)
 	lock.l_len = 0;
 	if (fcntl(sharetab_fd, F_SETLKW, &lock) < 0) {
 		perror("sharetab_lock: failed to lock");
-		return (-1);
+		return (errno);
 	}
 	return (0);
 }
@@ -217,7 +217,6 @@ sharetab_unlock(void)
 	return (retval);
 }
 
-
 static void
 update_sharetab(sa_handle_impl_t impl_handle)
 {
@@ -228,7 +227,6 @@ update_sharetab(sa_handle_impl_t impl_handle)
 	sa_fstype_t *fstype;
 	const char *resource;
 
-
 	temp_fd = mkstemp(tempfile);
 
 	if (temp_fd < 0)

lib/libzfs/libzfs_mount.c

@@ -871,7 +871,6 @@ zfs_share_proto(zfs_handle_t *zhp, zfs_share_proto_t *proto)
 	if (!zfs_is_mountable(zhp, mountpoint, sizeof (mountpoint), NULL))
 		return (0);
 
-	verify(sharetab_lock() == 0);
 	for (curr_proto = proto; *curr_proto != PROTO_END; curr_proto++) {
 		/*
 		 * Return success if there are no share options.
@@ -887,7 +886,6 @@ zfs_share_proto(zfs_handle_t *zhp, zfs_share_proto_t *proto)
 			(void) zfs_error_fmt(hdl, EZFS_SHARENFSFAILED,
 			    dgettext(TEXT_DOMAIN, "cannot share '%s': %s"),
 			    zfs_get_name(zhp), sa_errorstr(ret));
-			verify(sharetab_unlock() == 0);
 			return (-1);
 		}
 
@@ -919,7 +917,6 @@ zfs_share_proto(zfs_handle_t *zhp, zfs_share_proto_t *proto)
 				    proto_table[*curr_proto].p_share_err,
 				    dgettext(TEXT_DOMAIN, "cannot share '%s'"),
 				    zfs_get_name(zhp));
-				verify(sharetab_unlock() == 0);
 				return (-1);
 			}
 			hdl->libzfs_shareflags |= ZFSSHARE_MISS;
@@ -935,20 +932,17 @@ zfs_share_proto(zfs_handle_t *zhp, zfs_share_proto_t *proto)
 				    proto_table[*curr_proto].p_share_err,
 				    dgettext(TEXT_DOMAIN, "cannot share '%s'"),
 				    zfs_get_name(zhp));
-				verify(sharetab_unlock() == 0);
 				return (-1);
 			}
 		} else {
 			(void) zfs_error_fmt(hdl,
 			    proto_table[*curr_proto].p_share_err,
 			    dgettext(TEXT_DOMAIN, "cannot share '%s'"),
 			    zfs_get_name(zhp));
-			verify(sharetab_unlock() == 0);
 			return (-1);
 		}
 
 	}
-	verify(sharetab_unlock() == 0);
 	return (0);
 }