There is problem with previous communication mechanism, and we got below
deadlock scenario with cluster which has 3 nodes.
Sender Receiver Receiver
token(EX)
message(EX)
writes message
downconverts message(CR)
requests ack(EX)
get message(CR) gets message(CR)
reads message reads message
requests EX on message requests EX on message
To fix this problem, we do the following changes:
1. the sender downconverts MESSAGE to CW rather than CR.
2. and the receiver request PR lock not EX lock on message.
And in case we failed to down-convert EX to CW on message, it is better to
unlock message otherthan still hold the lock.
Reviewed-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
Signed-off-by: Lidong Zhong <ldzhong@suse.com>
Signed-off-by: Guoqing Jiang <gqjiang@suse.com>
Signed-off-by: NeilBrown <neilb@suse.com>
When node A stops an array while the array is doing a resync, we need
to let another node B take over the resync task.
To achieve the goal, we need the A send an explicit BITMAP_NEEDS_SYNC
message to the cluster. And the node B which received that message will
invoke __recover_slot to do resync.
Reviewed-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
Signed-off-by: Guoqing Jiang <gqjiang@suse.com>
Signed-off-by: NeilBrown <neilb@suse.com>
Make recover_slot as a wraper to __recover_slot, since the
logic of __recover_slot can be reused for the condition
when other nodes need to take over the resync job.
Signed-off-by: Guoqing Jiang <gqjiang@suse.com>
Signed-off-by: NeilBrown <neilb@suse.com>
During a node failure, We need to suspend read balancing so that the
reads are directed to the first device and stale data is not read.
Suspending writes is not required because these would be recorded and
synced eventually.
A new flag MD_CLUSTER_SUSPEND_READ_BALANCING is set in recover_prep().
area_resyncing() will respond true for the entire devices if this
flag is set and the request type is READ. The flag is cleared
in recover_done().
Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
Reported-By: David Teigland <teigland@redhat.com>
Signed-off-by: NeilBrown <neilb@suse.com>
When "re-add" is writted to /sys/block/mdXX/md/dev-YYY/state,
the clustered md:
1. Sends RE_ADD message with the desc_nr. Nodes receiving the message
clear the Faulty bit in their respective rdev->flags.
2. The node initiating re-add, gathers the bitmaps of all nodes
and copies them into the local bitmap. It does not clear the bitmap
from which it is copying.
3. Initiating node schedules a md recovery to sync the devices.
Signed-off-by: Guoqing Jiang <gqjiang@suse.com>
Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
Signed-off-by: NeilBrown <neilb@suse.de>
This adds "remove" capabilities for the clustered environment.
When a user initiates removal of a device from the array, a
REMOVE message with disk number in the array is sent to all
the nodes which kick the respective device in their own array.
This facilitates the removal of failed devices.
Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
Signed-off-by: NeilBrown <neilb@suse.de>
Since the node num of md-cluster is from zero, and
cinfo->slot_number represents the slot num of dlm,
no need to check for equality.
Signed-off-by: Guoqing Jiang <gqjiang@suse.com>
Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
Signed-off-by: NeilBrown <neilb@suse.de>
drivers/md/md-cluster.c:190:6: sparse: symbol 'recover_bitmaps' was not declared. Should it be static?
Signed-off-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: NeilBrown <neilb@suse.de>
A --cluster-confirm without an --add (by another node) can
crash the kernel.
Fix it by guarding it using a state.
Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
Signed-off-by: NeilBrown <neilb@suse.de>
Algorithm:
1. Node 1 issues mdadm --manage /dev/mdX --add /dev/sdYY which issues
ioctl(ADD_NEW_DISC with disc.state set to MD_DISK_CLUSTER_ADD)
2. Node 1 sends NEWDISK with uuid and slot number
3. Other nodes issue kobject_uevent_env with uuid and slot number
(Steps 4,5 could be a udev rule)
4. In userspace, the node searches for the disk, perhaps
using blkid -t SUB_UUID=""
5. Other nodes issue either of the following depending on whether the disk
was found:
ioctl(ADD_NEW_DISK with disc.state set to MD_DISK_CANDIDATE and
disc.number set to slot number)
ioctl(CLUSTERED_DISK_NACK)
6. Other nodes drop lock on no-new-devs (CR) if device is found
7. Node 1 attempts EX lock on no-new-devs
8. If node 1 gets the lock, it sends METADATA_UPDATED after unmarking the disk
as SpareLocal
9. If not (get no-new-dev lock), it fails the operation and sends METADATA_UPDATED
10. Other nodes understand if the device is added or not by reading the superblock again after receiving the METADATA_UPDATED message.
Signed-off-by: Lidong Zhong <lzhong@suse.com>
Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
If there is a resync going on, all nodes must suspend writes to the
range. This is recorded in the suspend_info/suspend_list.
If there is an I/O within the ranges of any of the suspend_info,
should_suspend will return 1.
Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
When a RESYNC_START message arrives, the node removes the entry
with the current slot number and adds the range to the
suspend_list.
Simlarly, when a RESYNC_FINISHED message is received, node clears
entry with respect to the bitmap number.
Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
When a resync is initiated, RESYNCING message is sent to all active
nodes with the range (lo,hi). When the resync is over, a RESYNCING
message is sent with (0,0). A high sector value of zero indicates
that the resync is over.
Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
Re-reads the devices by invalidating the cache.
Since we don't write to faulty devices, this is detected using
events recorded in the devices. If it is old as compared to the mddev
mark it is faulty.
Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
- request to send a message
- make changes to superblock
- send messages telling everyone that the superblock has changed
- other nodes all read the superblock
- other nodes all ack the messages
- updating node release the "I'm sending a message" resource.
Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
The sending part is split in two functions to make sure
atomicity of the operations, such as the MD superblock update.
Signed-off-by: Lidong Zhong <lzhong@suse.com>
Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
1. receive status
sender receiver receiver
ACK:CR ACK:CR ACK:CR
2. sender get EX of TOKEN
sender get EX of MESSAGE
sender receiver receiver
TOKEN:EX ACK:CR ACK:CR
MESSAGE:EX
ACK:CR
3. sender write LVB.
sender down-convert MESSAGE from EX to CR
sender try to get EX of ACK
[ wait until all receiver has *processed* the MESSAGE ]
[ triggered by bast of ACK ]
receiver get CR of MESSAGE
receiver read LVB
receiver processes the message
[ wait finish ]
receiver release ACK
sender receiver receiver
TOKEN:EX MESSAGE:CR MESSAGE:CR
MESSAGE:CR
ACK:EX
4. sender down-convert ACK from EX to CR
sender release MESSAGE
sender release TOKEN
receiver upconvert to EX of MESSAGE
receiver get CR of ACK
receiver release MESSAGE
sender receiver receiver
ACK:CR ACK:CR ACK:CR
Signed-off-by: Lidong Zhong <lzhong@suse.com>
Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
The DLM informs us in case of node failure with the DLM slot number.
cluster_info->recovery_map sets the bit corresponding to the slot number
and wakes up the recovery thread.
The recovery thread:
1. Derives the slot number from the recovery_map
2. Locks the bitmap corresponding to the slot
3. Copies the set bits to the node-local bitmap
Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
When a node joins, it does not know of other nodes performing resync.
So, each node keeps the resync information in it's LVB. When a new
node joins, it reads the LVB of each "online" bitmap.
[TODO] The new node attempts to get the PW lock on other bitmap, if
it is successful, it reads the bitmap and performs the resync (if
required) on it's behalf.
If the node does not get the PW, it requests CR and reads the LVB
for the resync information.
Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
On-disk format:
0 4k 8k 12k
-------------------------------------------------------------------
| idle | md super | bm super [0] + bits |
| bm bits[0, contd] | bm super[1] + bits | bm bits[1, contd] |
| bm super[2] + bits | bm bits [2, contd] | bm super[3] + bits |
| bm bits [3, contd] | | |
Bitmap super has a field nodes, which defines the maximum number
of nodes the device can use. While reading the bitmap super, if
the cluster finds out that the number of nodes is > 0:
1. Requests the md-cluster module.
2. Calls md_cluster_ops->join(), which sets up clustering such as
joining DLM lockspace.
Since the first time, the first bitmap is read. After the call
to the cluster_setup, the bitmap offset is adjusted and the
superblock is re-read. This also ensures the bitmap is read
the bitmap lock (when bitmap lock is introduced in later patches)
Questions:
1. cluster name is repeated in all bitmap supers. Is that okay?
Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
DLM offers callbacks when a node fails and the lock remastery
is performed:
1. recover_prep: called when DLM discovers a node is down
2. recover_slot: called when DLM identifies the node and recovery
can start
3. recover_done: called when all nodes have completed recover_slot
recover_slot() and recover_done() are also called when the node joins
initially in order to inform the node with its slot number. These slot
numbers start from one, so we deduct one to make it start with zero
which the cluster-md code uses.
Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
md_cluster_info stores the cluster information in the MD device.
The join() is called when mddev detects it is a clustered device.
The main responsibilities are:
1. Setup a DLM lockspace
2. Setup all initial locks such as super block locks and bitmap lock (will come later)
The leave() clears up the lockspace and all the locks held.
Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
A dlm_lock_resource is a structure which contains all information
required for locking using DLM. The init function allocates the
lock and acquires the lock in NL mode. The unlock function
converts the lock resource to NL mode. This is done to preserve
LVB and for faster processing of locks. The lock resource is
DLM unlocked only in the lockres_free function, which is the end
of life of the lock resource.
Signed-off-by: Lidong Zhong <lzhong@suse.com>
Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
