mds: don't send resolve message between active MDS

When MDS cluster is resolving, current behavior is sending subtree resolve
message to all other MDS and waiting for all other MDS' resolve message.
The problem is that active MDS can have diffent subtree map due to rename.
Besides gathering active MDS's resolve messages are also racy. The only
function for these messages is disambiguate other MDS' import. We can
replace it by import finish notification.

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
mds: set resolve/rejoin gather MDS set in advance

For active MDS, it may receive resolve/resolve message before receiving
the mdsmap message that claims the MDS cluster is in resolving/rejoning
state. So instead of set the gather MDS set when receiving the mdsmap.
set them in advance when detecting MDS' failure.

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
mds: don't send MDentry{Link,Unlink} before receiving cache rejoin

The active MDS calls MDCache::rejoin_scour_survivor_replicas() when it
receives the cache rejoin message. The function will remove the objects
replicated by MDentry{Link,Unlink} from replica map.

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
mds: send cache rejoin messages after gathering all resolves

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
mds: send resolve acks after master updates are safely logged

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
mds: fix MDS recovery involving cross authority rename

For mds cluster, rename operation may involve multiple MDS. If the
rename source's auth MDS crashes after some witness MDS have prepared
the rename but before the rename is committing. Later when the MDS
recovers, its subtree map and linkages are different from the prepared
MDS'. This causes problems for both subtree resolve and cache rejoin.
The solution is, if the rename source's auth MDS fails, the prepared
witness MDS query the master MDS if the operation is committing. If
it's not, rollback the rename, then send resolve message to the
recovering MDS.

Another similar case is a prepared witness MDS crashes when the
rename source's auth MDS has prepared or is preparing the operation.
when the witness recovers, the master just delay sending the resolve
ack message until the it commits the operation.

This patch also updates Server::handle_client_rename(). Make preparing
the rename source's auth MDS be the final step before committing the
rename.

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
mds: remove MDCache::rejoin_fetch_dirfrags()

In commit 77946dcdae (mds: fetch missing inodes from disk), I introduced
MDCache::rejoin_fetch_dirfrags(). But it basicly duplicates the function
of MDCache::open_undef_dirfrags(), so just remove rejoin_fetch_dirfrags()
and make open_undef_dirfrags() also handle undefined inodes.

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
mds: include replica nonce in MMDSCacheRejoin::inode_strong

So the recovering MDS can properly handle cache expire messages.
Also increase the nonce value when sending the cache rejoin acks.

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
mds: encode dirfrag base in cache rejoin ack

Cache rejoin ack message already encodes inode base, make it also encode
dirfrag base. This allowes the message to replicate stray dentries like
MDentryUnlink message. The function will be used by later patch.

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
mds: handle linkage mismatch during cache rejoin

For MDS cluster, not all file system namespace operations that impact
multiple MDS use two phase commit. Some operations use dentry link/unlink
message to update replica dentry's linkage after they are committed by
the master MDS. It's possible the master MDS crashes after journaling an
operation, but before sending the dentry link/unlink messages. Later when
the MDS recovers and receives cache rejoin messages from the surviving
MDS, it will find linkage mismatch.

The original cache rejoin code does not properly handle the case that
dentry unlink messages were missing. Unlinked inodes were linked to stray
dentries. So the cache rejoin ack message need push replicas of these
stray dentries to the surviving MDS.

This patch also adds code that handles cache expiration in the middle of
cache rejoining.

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
mds: reqid for rejoinning authpin/wrlock need to be list

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
mds: take object's versionlock when rejoinning xlock

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
mds: share inode max size after MDS recovers

The MDS may crash after journaling the new max size, but before sending
the new max size to the client. Later when the MDS recovers, the client
re-requests the new max size, but the MDS finds max size unchanged. So
the client waits for the new max size forever. This issue can be avoided
by checking client cap's last_sent, share inode max size if it is zero.
(reconnected cap's last_sent is zero)

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
mds: issue caps when lock state in replica become SYNC

because client can request READ caps from non-auth MDS.

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
mds: send lock action message when auth MDS is in proper state.

For rejoining object, don't send lock ACK message because lock states
are still uncertain. The lock ACK may confuse object's auth MDS and
trigger assertion.

If object's auth MDS is not active, just skip sending NUDGE, REQRDLOCK
and REQSCATTER messages. MDCache::handle_mds_recovery() will take care
of them.

Also defer caps release message until clientreplay or active

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
mds: add dirty imported dirfrag to LogSegment

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
mds: avoid double auth pin for file recovery

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
mds: check MDS peer's state through mdsmap

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
mds: unfreeze subtree if import aborts in PREPPED state

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
mds: fix export cancel notification

The comment says that if the importer is dead, bystanders thinks the
exporter is the only auth, as per mdcache->handle_mds_failure(). But
there is no such code in MDCache::handle_mds_failure().

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>