md: add 'recovery_start' per-device sysfs attribute

Enable external metadata arrays to manage rebuild checkpointing via a
md/dev-XXX/recovery_start attribute which reflects rdev->recovery_offset

Also update resync_start_store to allow 'none' to be written, for
consistency.

Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: NeilBrown <neilb@suse.de>

1 files changed, 23 insertions, 4 deletions

diff --git a/Documentation/md.txt b/Documentation/md.txt
index 21d26fb5d02b..188f4768f1d5 100644
--- a/Documentation/md.txt
+++ b/Documentation/md.txt
@@ -233,9 +233,9 @@ All md devices contain:
 
   resync_start
      The point at which resync should start.  If no resync is needed,
-     this will be a very large number.  At array creation it will
-     default to 0, though starting the array as 'clean' will
-     set it much larger.
+     this will be a very large number (or 'none' since 2.6.30-rc1).  At
+     array creation it will default to 0, though starting the array as
+     'clean' will set it much larger.
 
    new_dev
      This file can be written but not read.  The value written should
@@ -379,8 +379,9 @@ Each directory contains:
         Writing "writemostly" sets the writemostly flag.
         Writing "-writemostly" clears the writemostly flag.
         Writing "blocked" sets the "blocked" flag.
-        Writing "-blocked" clear the "blocked" flag and allows writes
+        Writing "-blocked" clears the "blocked" flag and allows writes
                 to complete.
+        Writing "in_sync" sets the in_sync flag.
 
         This file responds to select/poll. Any change to 'faulty'
         or 'blocked' causes an event.
@@ -417,6 +418,24 @@ Each directory contains:
         array.  If a value less than the current component_size is
         written, it will be rejected.
 
+      recovery_start
+
+        When the device is not 'in_sync', this records the number of
+        sectors from the start of the device which are known to be
+        correct.  This is normally zero, but during a recovery
+        operation is will steadily increase, and if the recovery is
+        interrupted, restoring this value can cause recovery to
+        avoid repeating the earlier blocks.  With v1.x metadata, this
+        value is saved and restored automatically.
+
+        This can be set whenever the device is not an active member of
+        the array, either before the array is activated, or before
+        the 'slot' is set.
+
+        Setting this to 'none' is equivalent to setting 'in_sync'.
+        Setting to any other value also clears the 'in_sync' flag.
+        
+
 
 An active md device will also contain and entry for each active device
 in the array.  These are named