Add zpool_events_seek() functionality

The ZFS_IOC_EVENTS_SEEK ioctl was added to allow user space callers
to seek around the zevent file descriptor by EID.  When a specific
EID is passed and it exists the cursor will be positioned there.
If the EID is no longer cached by the kernel ENOENT is returned.
The caller may also pass ZEVENT_SEEK_START or ZEVENT_SEEK_END to seek
to those respective locations.

Signed-off-by: Brian Behlendorf <[email protected]>
Signed-off-by: Chris Dunlap <[email protected]>
Issue #2

1 files changed, 36 insertions, 0 deletions

diff --git a/lib/libzfs/libzfs_pool.c b/lib/libzfs/libzfs_pool.c
index b822ace68..1b8f3b63a 100644
--- a/lib/libzfs/libzfs_pool.c
+++ b/lib/libzfs/libzfs_pool.c
@@ -3870,6 +3870,42 @@ zpool_events_clear(libzfs_handle_t *hdl, int *count)
 	return (0);
 }
 
+/*
+ * Seek to a specific EID, ZEVENT_SEEK_START, or ZEVENT_SEEK_END for
+ * the passed zevent_fd file handle.  On success zero is returned,
+ * otherwise -1 is returned and hdl->libzfs_error is set to the errno.
+ */
+int
+zpool_events_seek(libzfs_handle_t *hdl, uint64_t eid, int zevent_fd)
+{
+	zfs_cmd_t zc = {"\0"};
+	int error = 0;
+
+	zc.zc_guid = eid;
+	zc.zc_cleanup_fd = zevent_fd;
+
+	if (zfs_ioctl(hdl, ZFS_IOC_EVENTS_SEEK, &zc) != 0) {
+		switch (errno) {
+		case ENOENT:
+			error = zfs_error_fmt(hdl, EZFS_NOENT,
+			    dgettext(TEXT_DOMAIN, "cannot get event"));
+			break;
+
+		case ENOMEM:
+			error = zfs_error_fmt(hdl, EZFS_NOMEM,
+			    dgettext(TEXT_DOMAIN, "cannot get event"));
+			break;
+
+		default:
+			error = zpool_standard_error_fmt(hdl, errno,
+			    dgettext(TEXT_DOMAIN, "cannot get event"));
+			break;
+		}
+	}
+
+	return (error);
+}
+
 void
 zpool_obj_to_path(zpool_handle_t *zhp, uint64_t dsobj, uint64_t obj,
     char *pathname, size_t len)