OpenZFS 7180 - potential race between zfs_suspend_fs+zfs_resume_fs and zfs_ioc_rename

Authored by: Andriy Gapon <[email protected]>
Reviewed by: Matt Ahrens <[email protected]>
Reviewed by: Pavel Zakharov <[email protected]>
Approved by: Richard Lowe <[email protected]>
Reviewed-by: Brian Behlendorf <[email protected]>
Ported-by: George Melikov <[email protected]>

OpenZFS-issue: https://www.illumos.org/issues/7180
OpenZFS-commit: https://github.com/openzfs/openzfs/commit/690041b
Closes #5627 

3 files changed, 18 insertions, 11 deletions

diff --git a/include/sys/zfs_vfsops.h b/include/sys/zfs_vfsops.h
index b59ace5b1..870eb9727 100644
--- a/include/sys/zfs_vfsops.h
+++ b/include/sys/zfs_vfsops.h
@@ -181,7 +181,7 @@ typedef struct zfid_long {
 extern uint_t zfs_fsyncer_key;
 
 extern int zfs_suspend_fs(zfs_sb_t *zsb);
-extern int zfs_resume_fs(zfs_sb_t *zsb, const char *osname);
+extern int zfs_resume_fs(zfs_sb_t *zsb, struct dsl_dataset *ds);
 extern int zfs_userspace_one(zfs_sb_t *zsb, zfs_userquota_prop_t type,
     const char *domain, uint64_t rid, uint64_t *valuep);
 extern int zfs_userspace_many(zfs_sb_t *zsb, zfs_userquota_prop_t type,
diff --git a/module/zfs/zfs_ioctl.c b/module/zfs/zfs_ioctl.c
index 659345917..8ae4300f5 100644
--- a/module/zfs/zfs_ioctl.c
+++ b/module/zfs/zfs_ioctl.c
@@ -3645,12 +3645,15 @@ zfs_ioc_rollback(const char *fsname, nvlist_t *args, nvlist_t *outnvl)
 	int error;
 
 	if (get_zfs_sb(fsname, &zsb) == 0) {
+		dsl_dataset_t *ds;
+
+		ds = dmu_objset_ds(zsb->z_os);
 		error = zfs_suspend_fs(zsb);
 		if (error == 0) {
 			int resume_err;
 
 			error = dsl_dataset_rollback(fsname, zsb, outnvl);
-			resume_err = zfs_resume_fs(zsb, fsname);
+			resume_err = zfs_resume_fs(zsb, ds);
 			error = error ? error : resume_err;
 		}
 		deactivate_super(zsb->z_sb);
@@ -4248,8 +4251,10 @@ zfs_ioc_recv_impl(char *tofs, char *tosnap, char *origin,
 
 		if (get_zfs_sb(tofs, &zsb) == 0) {
 			/* online recv */
+			dsl_dataset_t *ds;
 			int end_err;
 
+			ds = dmu_objset_ds(zsb->z_os);
 			error = zfs_suspend_fs(zsb);
 			/*
 			 * If the suspend fails, then the recv_end will
@@ -4257,7 +4262,7 @@ zfs_ioc_recv_impl(char *tofs, char *tosnap, char *origin,
 			 */
 			end_err = dmu_recv_end(&drc, zsb);
 			if (error == 0)
-				error = zfs_resume_fs(zsb, tofs);
+				error = zfs_resume_fs(zsb, ds);
 			error = error ? error : end_err;
 			deactivate_super(zsb->z_sb);
 		} else if ((zv = zvol_suspend(tofs)) != NULL) {
@@ -4944,11 +4949,14 @@ zfs_ioc_userspace_upgrade(zfs_cmd_t *zc)
 			 * objset needs to be closed & reopened (to grow the
 			 * objset_phys_t).  Suspend/resume the fs will do that.
 			 */
+			dsl_dataset_t *ds;
+
+			ds = dmu_objset_ds(zsb->z_os);
 			error = zfs_suspend_fs(zsb);
 			if (error == 0) {
 				dmu_objset_refresh_ownership(zsb->z_os,
 				    zsb);
-				error = zfs_resume_fs(zsb, zc->zc_name);
+				error = zfs_resume_fs(zsb, ds);
 			}
 		}
 		if (error == 0)
diff --git a/module/zfs/zfs_vfsops.c b/module/zfs/zfs_vfsops.c
index 65efcdce5..20ff165d9 100644
--- a/module/zfs/zfs_vfsops.c
+++ b/module/zfs/zfs_vfsops.c
@@ -1710,7 +1710,7 @@ EXPORT_SYMBOL(zfs_suspend_fs);
  * Reopen zfs_sb_t and release VFS ops.
  */
 int
-zfs_resume_fs(zfs_sb_t *zsb, const char *osname)
+zfs_resume_fs(zfs_sb_t *zsb, dsl_dataset_t *ds)
 {
 	int err, err2;
 	znode_t *zp;
@@ -1720,13 +1720,12 @@ zfs_resume_fs(zfs_sb_t *zsb, const char *osname)
 	ASSERT(RW_WRITE_HELD(&zsb->z_teardown_inactive_lock));
 
 	/*
-	 * We already own this, so just hold and rele it to update the
-	 * objset_t, as the one we had before may have been evicted.
+	 * We already own this, so just update the objset_t, as the one we
+	 * had before may have been evicted.
 	 */
-	VERIFY0(dmu_objset_hold(osname, zsb, &zsb->z_os));
-	VERIFY3P(zsb->z_os->os_dsl_dataset->ds_owner, ==, zsb);
-	VERIFY(dsl_dataset_long_held(zsb->z_os->os_dsl_dataset));
-	dmu_objset_rele(zsb->z_os, zsb);
+	VERIFY3P(ds->ds_owner, ==, zsb);
+	VERIFY(dsl_dataset_long_held(ds));
+	VERIFY0(dmu_objset_from_ds(ds, &zsb->z_os));
 
 	/*
 	 * Make sure version hasn't changed