Merge pull request openzfs#6 from bgly/spp-10.1.6

SPPSUP-1149: Fix sharenfs issues with locking

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);

include/sys/fs/zfs.h

@@ -1142,6 +1142,7 @@ typedef struct ddt_histogram {
 #define	ZFS_DRIVER	"zfs"
 #define	ZFS_DEV		"/dev/zfs"
 #define	ZFS_SHARETAB	"/etc/dfs/sharetab"
+#define	ZFS_SHARETAB_LOCK	"/etc/dfs/sharetab.lck"
 
 #define	ZFS_SUPER_MAGIC	0x2fc12fc1
 

lib/libshare/libshare.c

@@ -26,6 +26,7 @@
 
 #include <stdio.h>
 #include <stdlib.h>
+#include <fcntl.h>
 #include <errno.h>
 #include <strings.h>
 #include <libintl.h>
@@ -165,6 +166,57 @@ parse_sharetab(sa_handle_impl_t impl_handle)
 	fclose(fp);
 }
 
+static int sharetab_fd = -1;
+
+int
+sharetab_lock(void)
+{
+	struct flock lock;
+
+	verify(sharetab_fd == -1);
+
+	if (mkdir("/etc/dfs", 0755) < 0 && errno != EEXIST) {
+		perror("sharetab_lock: failed to create /etc/dfs");
+		return (errno);
+	}
+
+	sharetab_fd = open(ZFS_SHARETAB_LOCK, (O_RDWR | O_CREAT), 0600);
+
+	if (sharetab_fd < 0) {
+		perror("sharetab_lock: failed to open");
+		return (errno);
+	}
+
+	lock.l_type = F_WRLCK;
+	lock.l_whence = SEEK_SET;
+	lock.l_start = 0;
+	lock.l_len = 0;
+	if (fcntl(sharetab_fd, F_SETLKW, &lock) < 0) {
+		perror("sharetab_lock: failed to lock");
+		return (errno);
+	}
+	return (0);
+}
+
+int
+sharetab_unlock(void)
+{
+	struct flock lock;
+	int retval = -1;
+
+	if (sharetab_fd < 0)
+		return (-1);
+	lock.l_type = F_UNLCK;
+	lock.l_whence = SEEK_SET;
+	lock.l_start = 0;
+	lock.l_len = 0;
+	if (fcntl(sharetab_fd, F_SETLK, &lock) == 0)
+		retval = 0;
+	close(sharetab_fd);
+	sharetab_fd = -1;
+	return (retval);
+}
+
 static void
 update_sharetab(sa_handle_impl_t impl_handle)
 {
@@ -175,10 +227,6 @@ update_sharetab(sa_handle_impl_t impl_handle)
 	sa_fstype_t *fstype;
 	const char *resource;
 
-	if (mkdir("/etc/dfs", 0755) < 0 && errno != EEXIST) {
-		return;
-	}
-
 	temp_fd = mkstemp(tempfile);
 
 	if (temp_fd < 0)

lib/libspl/include/libshare.h

@@ -83,6 +83,9 @@ extern sa_share_t sa_find_share(sa_handle_t, char *);
 extern int sa_enable_share(sa_group_t, char *);
 extern int sa_disable_share(sa_share_t, char *);
 
+extern int sharetab_lock(void);
+extern int sharetab_unlock(void);
+
 /* protocol specific interfaces */
 extern int sa_parse_legacy_options(sa_group_t, char *, char *);
 

tests/test-runner/bin/zts-report.py

@@ -272,6 +272,7 @@
     'snapshot/clone_001_pos': ['FAIL', known_reason],
     'snapshot/snapshot_009_pos': ['FAIL', '7961'],
     'snapshot/snapshot_010_pos': ['FAIL', '7961'],
+    'snapshot/rollback_003_pos': ['FAIL', '6143'],
     'snapused/snapused_004_pos': ['FAIL', '5513'],
     'tmpfile/setup': ['SKIP', tmpfile_reason],
     'threadsappend/threadsappend_001_pos': ['FAIL', '6136'],