Merge tag 'md-3.3' of git://neil.brown.name/md

md update for 3.3

Big change is new hot-replacement.
A slot in an array can hold 2 devices - one that
wants-replacement and one that is the replacement.
Once the replacement is built - either from the
original or (in the case of errors) from elsewhere,
the wants-replacement device will be removed.

* tag 'md-3.3' of git://neil.brown.name/md: (36 commits)
  md/raid1: Mark device want_replacement when we see a write error.
  md/raid1: If there is a spare and a want_replacement device, start replacement.
  md/raid1: recognise replacements when assembling arrays.
  md/raid1: handle activation of replacement device when recovery completes.
  md/raid1: Allow a failed replacement device to be removed.
  md/raid1: Allocate spare to store replacement devices and their bios.
  md/raid1:  Replace use of mddev->raid_disks with conf->raid_disks.
  md/raid10: If there is a spare and a want_replacement device, start replacement.
  md/raid10: recognise replacements when assembling array.
  md/raid10: Allow replacement device to be replace old drive.
  md/raid10: handle recovery of replacement devices.
  md/raid10:  Handle replacement devices during resync.
  md/raid10: writes should get directed to replacement as well as original.
  md/raid10: allow removal of failed replacement devices.
  md/raid10: preferentially read from replacement device if possible.
  md/raid10:  change read_balance to return an rdev
  md/raid10: prepare data structures for handling replacement.
  md/raid5: Mark device want_replacement when we see a write error.
  md/raid5: If there is a spare and a want_replacement device, start replacement.
  md/raid5: recognise replacements when assembling array.
  ...

1 files changed, 18 insertions, 4 deletions

diff --git a/Documentation/md.txt b/Documentation/md.txt
index fc94770f44ab..993fba37b7d1 100644
--- a/Documentation/md.txt
+++ b/Documentation/md.txt
@@ -357,14 +357,14 @@ Each directory contains:
         written to, that device.
 
       state
-        A file recording the current state of the device in the array
+        A file recording the current state of the device in the array
         which can be a comma separated list of
               faulty   - device has been kicked from active use due to
-                         a detected fault or it has unacknowledged bad
-                         blocks
+                         a detected fault, or it has unacknowledged bad
+                         blocks
               in_sync  - device is a fully in-sync member of the array
               writemostly - device will only be subject to read
-                         requests if there are no other options.
+                         requests if there are no other options.
                          This applies only to raid1 arrays.
               blocked  - device has failed, and the failure hasn't been
                          acknowledged yet by the metadata handler.
@@ -374,6 +374,13 @@ Each directory contains:
                          This includes spares that are in the process
                          of being recovered to
               write_error - device has ever seen a write error.
+              want_replacement - device is (mostly) working but probably
+                         should be replaced, either due to errors or
+                         due to user request.
+              replacement - device is a replacement for another active
+                         device with same raid_disk.
+
+
         This list may grow in future.
         This can be written to.
         Writing "faulty"  simulates a failure on the device.
@@ -386,6 +393,13 @@ Each directory contains:
         Writing "in_sync" sets the in_sync flag.
         Writing "write_error" sets writeerrorseen flag.
         Writing "-write_error" clears writeerrorseen flag.
+        Writing "want_replacement" is allowed at any time except to a
+                replacement device or a spare.  It sets the flag.
+        Writing "-want_replacement" is allowed at any time.  It clears
+                the flag.
+        Writing "replacement" or "-replacement" is only allowed before
+                starting the array.  It sets or clears the flag.
+
 
         This file responds to select/poll. Any change to 'faulty'
         or 'blocked' causes an event.