[PATCH 3.10 16/23] md: fix problem when adding device to read-only array with bitmap.

From: Greg Kroah-Hartman
Date: Thu Jan 23 2014 - 13:42:36 EST


3.10-stable review patch. If anyone has any objections, please let me know.

------------------

From: NeilBrown <neilb@xxxxxxx>

commit 8313b8e57f55b15e5b7f7fc5d1630bbf686a9a97 upstream.

If an array is started degraded, and then the missing device
is found it can be re-added and a minimal bitmap-based recovery
will bring it fully up-to-date.

If the array is read-only a recovery would not be allowed.
But also if the array is read-only and the missing device was
present very recently, then there could be no need for any
recovery at all, so we simply include the device in the read-only
array without any recovery.

However... if the missing device was removed a little longer ago
it could be missing some updates, but if a bitmap is present it will
be conditionally accepted pending a bitmap-based update. We don't
currently detect this case properly and will include that old
device into the read-only array with no recovery even though it really
needs a recovery.

This patch keeps track of whether a bitmap-based-recovery is really
needed or not in the new Bitmap_sync rdev flag. If that is set,
then the device will not be added to a read-only array.

Cc: Andrei Warkentin <andreiw@xxxxxxxxxx>
Fixes: d70ed2e4fafdbef0800e73942482bb075c21578b
Signed-off-by: NeilBrown <neilb@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
drivers/md/md.c | 18 +++++++++++++++---
drivers/md/md.h | 3 +++
2 files changed, 18 insertions(+), 3 deletions(-)

--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -1118,6 +1118,7 @@ static int super_90_validate(struct mdde
rdev->raid_disk = -1;
clear_bit(Faulty, &rdev->flags);
clear_bit(In_sync, &rdev->flags);
+ clear_bit(Bitmap_sync, &rdev->flags);
clear_bit(WriteMostly, &rdev->flags);

if (mddev->raid_disks == 0) {
@@ -1196,6 +1197,8 @@ static int super_90_validate(struct mdde
*/
if (ev1 < mddev->bitmap->events_cleared)
return 0;
+ if (ev1 < mddev->events)
+ set_bit(Bitmap_sync, &rdev->flags);
} else {
if (ev1 < mddev->events)
/* just a hot-add of a new device, leave raid_disk at -1 */
@@ -1604,6 +1607,7 @@ static int super_1_validate(struct mddev
rdev->raid_disk = -1;
clear_bit(Faulty, &rdev->flags);
clear_bit(In_sync, &rdev->flags);
+ clear_bit(Bitmap_sync, &rdev->flags);
clear_bit(WriteMostly, &rdev->flags);

if (mddev->raid_disks == 0) {
@@ -1686,6 +1690,8 @@ static int super_1_validate(struct mddev
*/
if (ev1 < mddev->bitmap->events_cleared)
return 0;
+ if (ev1 < mddev->events)
+ set_bit(Bitmap_sync, &rdev->flags);
} else {
if (ev1 < mddev->events)
/* just a hot-add of a new device, leave raid_disk at -1 */
@@ -2829,6 +2835,7 @@ slot_store(struct md_rdev *rdev, const c
else
rdev->saved_raid_disk = -1;
clear_bit(In_sync, &rdev->flags);
+ clear_bit(Bitmap_sync, &rdev->flags);
err = rdev->mddev->pers->
hot_add_disk(rdev->mddev, rdev);
if (err) {
@@ -5761,6 +5768,7 @@ static int add_new_disk(struct mddev * m
info->raid_disk < mddev->raid_disks) {
rdev->raid_disk = info->raid_disk;
set_bit(In_sync, &rdev->flags);
+ clear_bit(Bitmap_sync, &rdev->flags);
} else
rdev->raid_disk = -1;
} else
@@ -7694,7 +7702,8 @@ static int remove_and_add_spares(struct
if (test_bit(Faulty, &rdev->flags))
continue;
if (mddev->ro &&
- rdev->saved_raid_disk < 0)
+ ! (rdev->saved_raid_disk >= 0 &&
+ !test_bit(Bitmap_sync, &rdev->flags)))
continue;

rdev->recovery_offset = 0;
@@ -7775,9 +7784,12 @@ void md_check_recovery(struct mddev *mdd
* As we only add devices that are already in-sync,
* we can activate the spares immediately.
*/
- clear_bit(MD_RECOVERY_NEEDED, &mddev->recovery);
remove_and_add_spares(mddev, NULL);
- mddev->pers->spare_active(mddev);
+ /* There is no thread, but we need to call
+ * ->spare_active and clear saved_raid_disk
+ */
+ md_reap_sync_thread(mddev);
+ clear_bit(MD_RECOVERY_NEEDED, &mddev->recovery);
goto unlock;
}

--- a/drivers/md/md.h
+++ b/drivers/md/md.h
@@ -129,6 +129,9 @@ struct md_rdev {
enum flag_bits {
Faulty, /* device is known to have a fault */
In_sync, /* device is in_sync with rest of array */
+ Bitmap_sync, /* ..actually, not quite In_sync. Need a
+ * bitmap-based recovery to get fully in sync
+ */
Unmerged, /* device is being added to array and should
* be considerred for bvec_merge_fn but not
* yet for actual IO


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