md-cluster: Improve md_reload_sb to be less error prone

md_reload_sb is too simplistic and it explicitly needs to determine
the changes made by the writing node. However, there are multiple areas
where a simple reload could fail.

Instead, read the superblock of one of the "good" rdevs and update
the necessary information:

- read the superblock into a newly allocated page, by temporarily
  swapping out rdev->sb_page and calling ->load_super.
- if that fails return
- if it succeeds, call check_sb_changes
  1. iterates over list of active devices and checks the matching
   dev_roles[] value.
   	If that is 'faulty', the device must be  marked as faulty
	 - call md_error to mark the device as faulty. Make sure
	   not to set CHANGE_DEVS and wakeup mddev->thread or else
	   it would initiate a resync process, which is the responsibility
	   of the "primary" node.
	 - clear the Blocked bit
	 - Call remove_and_add_spares() to hot remove the device.
	If the device is 'spare':
	 - call remove_and_add_spares() to get the number of spares
	   added in this operation.
	 - Reduce mddev->degraded to mark the array as not degraded.
  2. reset recovery_cp
- read the rest of the rdevs to update recovery_offset. If recovery_offset
  is equal to MaxSector, call spare_active() to set it In_sync

This required that recovery_offset be initialized to MaxSector, as
opposed to zero so as to communicate the end of sync for a rdev.

Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com>

1 files changed, 9 insertions, 0 deletions

diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
index 1dd13bb52940..b54fefc85b66 100644
--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -1592,6 +1592,15 @@ static int raid1_add_disk(struct mddev *mddev, struct md_rdev *rdev)
 	if (rdev->raid_disk >= 0)
 		first = last = rdev->raid_disk;
 
+	/*
+	 * find the disk ... but prefer rdev->saved_raid_disk
+	 * if possible.
+	 */
+	if (rdev->saved_raid_disk >= 0 &&
+	    rdev->saved_raid_disk >= first &&
+	    conf->mirrors[rdev->saved_raid_disk].rdev == NULL)
+		first = last = rdev->saved_raid_disk;
+
 	for (mirror = first; mirror <= last; mirror++) {
 		p = conf->mirrors+mirror;
 		if (!p->rdev) {