btrfs-progs: add option for recursive subvol snapshots

Documentation/btrfs-subvolume.rst

@@ -112,6 +112,15 @@ delete [options] [<subvolume> [<subvolume>...]], delete -i|--subvolid <subvolid>
         -i|--subvolid <subvolid>
                 subvolume id to be removed instead of the <path> that should point to the
                 filesystem with the subvolume
+
+        -R|--recursive
+                delete subvolumes beneath each subvolume recursively
+
+                This requires either `CAP_SYS_ADMIN` or the filesystem must be
+                mounted with `user_subvol_rm_allowed` mount option.
+                In the unprivileged case, subvolumes which cannot be accessed
+                are skipped.  The deletion is not atomic.
+
         -v|--verbose
                 (deprecated) alias for global *-v* option
 
@@ -243,17 +252,23 @@ show [options] <path>
         -u|--uuid UUID
                 show details about subvolume with the given *UUID*, looked up in *path*
 
-snapshot [-r] [-i <qgroupid>] <source> <dest>|[<dest>/]<name>
+snapshot [-r|-R|--recursive] [-i <qgroupid>] <source> <dest>|[<dest>/]<name>
         Create a snapshot of the subvolume *source* with the
         name *name* in the *dest* directory.
 
         If only *dest* is given, the subvolume will be named the basename of *source*.
         If *source* is not a subvolume, btrfs returns an error.
 
+        If you wish to recursively create a readonly snapshot, you can run
+        :command:`btrfs property set <path> ro true` on each subvolume after this command completes.
+
         ``Options``
 
         -r
                 Make the new snapshot read only.
+        -R|--recursive
+                Recursively snapshot subvolumes beneath the source. This option cannot be
+                combined with -r.
         -i <qgroupid>
                 Add the newly created subvolume to a qgroup. This option can be given multiple
                 times.

Documentation/mkfs.btrfs.rst

@@ -155,6 +155,29 @@ OPTIONS
                 contain the files from *rootdir*. Since version 4.14.1 the filesystem size is
                 not minimized. Please see option *--shrink* if you need that functionality.
 
+-u|--subvol <subdir>:<flags>
+        Specify that *subdir* is to be created as a subvolume rather than a regular
+        directory.  The option *--rootdir* must also be specified, and *subdir* must be an
+        existing subdirectory within it.  This option can be specified multiple times.
+
+        *flags* is an optional comma-separated list of modifiers. Valid choices are:
+
+        * *default*: create as default subvolume (this can only be specified once)
+        * *ro*: create as readonly subvolume
+
+	If there are hard links inside *rootdir* and *subdir* will split the
+	subvolumes, like the following case::
+
+		rootdir/
+		|- hardlink1
+		|- hardlink2
+		|- subdir/  <- will be a subvolume
+		   |- hardlink3
+
+	In that case we cannot create `hardlink3` as hardlinks of
+	`hardlink1` and `hardlink2` because hardlink3 will be inside a new
+	subvolume.
+
 --shrink
         Shrink the filesystem to its minimal size, only works with *--rootdir* option.