btrfs-progs: docs: update check options

Signed-off-by: David Sterba <dsterba@suse.com>

Documentation/btrfs-check.asciidoc

@@ -25,8 +25,12 @@ OPTIONS
 -s|--super <superblock>::
 use <superblock>th superblock copy, valid values are 0 up to 2 if the
 respective superblock offset is within the filesystem
+-b|--backup::
+use the first backup roots stored in the superblock that is valid
 --repair::
 try to repair the filesystem
+--readonly::
+run in read-only mode (default)
 --init-csum-tree::
 create a new CRC tree and recalculate all checksums
 --init-extent-tree::
@@ -37,10 +41,12 @@ verify checksums of data blocks
 indicate progress at various checking phases
 --qgroup-report::
 verify qgroup accounting and compare against filesystem accounting
---subvol-extents <subvolid>::
-show extent state for a subvolume
---tree-root <bytenr>::
+-E|--subvol-extents <subvolid>::
+show extent state for the given subvolume
+-r|--tree-root <bytenr>::
 use the given bytenr for the tree root
+--chunk-root <bytenr>::
+use the given bytenr for the chunk tree root
 
 EXIT STATUS
 -----------

cmds-check.c

@@ -9470,7 +9470,7 @@ const char * const cmd_check_usage[] = {
 	"WARNING: the repair mode is considered dangerous",
 	"",
 	"-s|--super <superblock>     use this superblock copy",
-	"-b|--backup                 use the backup root copy",
+	"-b|--backup                 use the first valid backup root copy",
 	"--repair                    try to repair the filesystem",
 	"--readonly                  run in read-only mode (default)",
 	"--init-csum-tree            create a new CRC tree",