btrfs-progs: docs: convert btrfs-rescue to rst

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

Documentation/btrfs-rescue.rst

@@ -0,0 +1,116 @@
+btrfs-rescue(8)
+===============
+
+SYNOPSIS
+--------
+
+**btrfs rescue** <subcommand> <args>
+
+DESCRIPTION
+-----------
+
+**btrfs rescue** is used to try to recover a damaged btrfs filesystem.
+
+SUBCOMMAND
+----------
+
+chunk-recover [options] <device>
+        Recover the chunk tree by scanning the devices
+
+        ``Options``
+
+        -y
+                assume an answer of *yes* to all questions.
+        -h
+                help.
+        -v
+                (deprecated) alias for global *-v* option
+
+
+.. note::
+   Since **chunk-recover** will scan the whole device, it will be very
+   slow especially executed on a large device.
+
+fix-device-size <device>
+        fix device size and super block total bytes values that are do not match
+
+        Kernel 4.11 starts to check the device size more strictly and this might
+        mismatch the stored value of total bytes. See the exact error message below.
+        Newer kernel will refuse to mount the filesystem where the values do not match.
+        This error is not fatal and can be fixed.  This command will fix the device
+        size values if possible.
+
+        .. code-block:: none
+
+                BTRFS error (device sdb): super_total_bytes 92017859088384 mismatch with fs_devices total_rw_bytes 92017859094528
+
+        The mismatch may also exhibit as a kernel warning:
+
+        .. code-block:: none
+
+                WARNING: CPU: 3 PID: 439 at fs/btrfs/ctree.h:1559 btrfs_update_device+0x1c5/0x1d0 [btrfs]
+
+super-recover [options] <device>
+        Recover bad superblocks from good copies.
+
+        ``Options``
+
+        -y
+                assume an answer of *yes* to all questions.
+        -v
+                (deprecated) alias for global *-v* option
+
+zero-log <device>
+        clear the filesystem log tree
+
+        This command will clear the filesystem log tree. This may fix a specific
+        set of problem when the filesystem mount fails due to the log replay. See below
+        for sample stacktraces that may show up in system log.
+
+        The common case where this happens was fixed a long time ago,
+        so it is unlikely that you will see this particular problem, but the command is
+        kept around.
+
+        .. note::
+                Clearing the log may lead to loss of changes that were made
+                since the last transaction commit. This may be up to 30 seconds
+                (default commit period) or less if the commit was implied by
+                other filesystem activity.
+
+        One can determine whether **zero-log** is needed according to the kernel
+        backtrace:
+
+        .. code-block:: none
+
+                ? replay_one_dir_item+0xb5/0xb5 [btrfs]
+                ? walk_log_tree+0x9c/0x19d [btrfs]
+                ? btrfs_read_fs_root_no_radix+0x169/0x1a1 [btrfs]
+                ? btrfs_recover_log_trees+0x195/0x29c [btrfs]
+                ? replay_one_dir_item+0xb5/0xb5 [btrfs]
+                ? btree_read_extent_buffer_pages+0x76/0xbc [btrfs]
+                ? open_ctree+0xff6/0x132c [btrfs]
+
+        If the errors are like above, then **zero-log** should be used to clear
+        the log and the filesystem may be mounted normally again. The keywords to look
+        for are 'open_ctree' which says that it's during mount and function names
+        that contain *replay*, *recover* or *log_tree*.
+
+EXIT STATUS
+-----------
+
+**btrfs rescue** returns a zero exit status if it succeeds. Non zero is
+returned in case of failure.
+
+AVAILABILITY
+------------
+
+*btrfs* is part of btrfs-progs.
+Please refer to the btrfs wiki http://btrfs.wiki.kernel.org for
+further details.
+
+SEE ALSO
+--------
+
+``mkfs.btrfs(8)``,
+``btrfs-scrub(8)``,
+``btrfs-check(8)``

Documentation/conf.py

@@ -46,4 +46,5 @@ man_pages = [
     ('btrfs-send', 'btrfs-send', 'generate a stream of changes between two subvolume snapshots', '', 8),
     ('btrfs-scrub', 'btrfs-scrub', 'scrub btrfs filesystem, verify block checksums', '', 8),
     ('btrfs-restore', 'btrfs-restore', 'try to restore files from a damaged filesystem image', '', 8),
+    ('btrfs-rescue', 'btrfs-rescue', 'recover a damaged btrfs filesystem', '', 8),
 ]

Documentation/man-index.rst

@@ -6,6 +6,7 @@ Manual pages
 .. toctree::
    :maxdepth: 1
 
+   btrfs-rescue
    btrfs-restore
    btrfs-scrub
    btrfs-select-super