MFC r331701: MFV r331695, 331700: 9166 zfs storage pool checkpoint

illumos/illumos-gate@8671400134a11c848244896ca51a7db4d0f69da4

The idea of Storage Pool Checkpoint (aka zpool checkpoint) deals with
exactly that.  It can be thought of as a “pool-wide snapshot” (or a
variation of extreme rewind that doesn’t corrupt your data).  It remembers
the entire state of the pool at the point that it was taken and the user
can revert back to it later or discard it.  Its generic use case is an
administrator that is about to perform a set of destructive actions to ZFS
as part of a critical procedure.  She takes a checkpoint of the pool before
performing the actions, then rewinds back to it if one of them fails or puts
the pool into an unexpected state.  Otherwise, she discards it.  With the
assumption that no one else is making modifications to ZFS, she basically
wraps all these actions into a “high-level transaction”.

Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Reviewed by: John Kennedy <john.kennedy@delphix.com>
Reviewed by: Dan Kimmel <dan.kimmel@delphix.com>
Approved by: Richard Lowe <richlowe@richlowe.net>
Author: Serapheim Dimitropoulos <serapheim.dimitro@delphix.com>

2 files changed, 71 insertions, 0 deletions

diff --git a/cddl/contrib/opensolaris/lib/libzfs_core/common/libzfs_core.c b/cddl/contrib/opensolaris/lib/libzfs_core/common/libzfs_core.c
index a7c973f..3dda533 100644
--- a/cddl/contrib/opensolaris/lib/libzfs_core/common/libzfs_core.c
+++ b/cddl/contrib/opensolaris/lib/libzfs_core/common/libzfs_core.c
@@ -999,6 +999,74 @@ lzc_channel_program(const char *pool, const char *program, uint64_t instrlimit,
 }
 
 /*
+ * Creates a checkpoint for the specified pool.
+ *
+ * If this function returns 0 the pool was successfully checkpointed.
+ *
+ * This method may also return:
+ *
+ * ZFS_ERR_CHECKPOINT_EXISTS
+ *	The pool already has a checkpoint. A pools can only have one
+ *	checkpoint at most, at any given time.
+ *
+ * ZFS_ERR_DISCARDING_CHECKPOINT
+ * 	ZFS is in the middle of discarding a checkpoint for this pool.
+ * 	The pool can be checkpointed again once the discard is done.
+ *
+ * ZFS_DEVRM_IN_PROGRESS
+ * 	A vdev is currently being removed. The pool cannot be
+ * 	checkpointed until the device removal is done.
+ *
+ * ZFS_VDEV_TOO_BIG
+ * 	One or more top-level vdevs exceed the maximum vdev size
+ * 	supported for this feature.
+ */
+int
+lzc_pool_checkpoint(const char *pool)
+{
+	int error;
+
+	nvlist_t *result = NULL;
+	nvlist_t *args = fnvlist_alloc();
+
+	error = lzc_ioctl(ZFS_IOC_POOL_CHECKPOINT, pool, args, &result);
+
+	fnvlist_free(args);
+	fnvlist_free(result);
+
+	return (error);
+}
+
+/*
+ * Discard the checkpoint from the specified pool.
+ *
+ * If this function returns 0 the checkpoint was successfully discarded.
+ *
+ * This method may also return:
+ *
+ * ZFS_ERR_NO_CHECKPOINT
+ * 	The pool does not have a checkpoint.
+ *
+ * ZFS_ERR_DISCARDING_CHECKPOINT
+ * 	ZFS is already in the middle of discarding the checkpoint.
+ */
+int
+lzc_pool_checkpoint_discard(const char *pool)
+{
+	int error;
+
+	nvlist_t *result = NULL;
+	nvlist_t *args = fnvlist_alloc();
+
+	error = lzc_ioctl(ZFS_IOC_POOL_DISCARD_CHECKPOINT, pool, args, &result);
+
+	fnvlist_free(args);
+	fnvlist_free(result);
+
+	return (error);
+}
+
+/*
  * Executes a read-only channel program.
  *
  * A read-only channel program works programmatically the same way as a
diff --git a/cddl/contrib/opensolaris/lib/libzfs_core/common/libzfs_core.h b/cddl/contrib/opensolaris/lib/libzfs_core/common/libzfs_core.h
index 5202fd1..0eaa89c 100644
--- a/cddl/contrib/opensolaris/lib/libzfs_core/common/libzfs_core.h
+++ b/cddl/contrib/opensolaris/lib/libzfs_core/common/libzfs_core.h
@@ -92,6 +92,9 @@ int lzc_channel_program(const char *, const char *, uint64_t,
 int lzc_channel_program_nosync(const char *, const char *, uint64_t,
     uint64_t, nvlist_t *, nvlist_t **);
 
+int lzc_pool_checkpoint(const char *);
+int lzc_pool_checkpoint_discard(const char *);
+
 #ifdef	__cplusplus
 }
 #endif