mds: trim empty non-auth dirfrags

Fragmenting a non-auth dirfrag results several smaller dirfrags. Some
of the resulting dirfrags can be empty, which are not used to connected
to auth subtree.

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
mds: don't trim ambiguous import dirfrags

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

return NULL if there is no opened dirfrag

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
mds: journal EFragment::OP_COMMIT before drop locks

Dropping locks can dispatch other requests. These request can submit
log entry.

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
mds: fix null pointer dereference in MDCache::rejoin_send_rejoins()

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
mds: skip non-opened session when flushing client sessions

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
mds: explicitly set nonce for imported dirfrag

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
mds: don't clear scatter dirty when cache rejoin ack is received

The auth mds has received dirty scatterlock state. But it hasn't
journaled the dirty state yet. The log segment that marked the
scatterlock dirty need to be preserved. Therefore, we can't clear
the dirty flag of scatterlock.

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
mds: fix stack overflow caused by nested dispatch

Commit bc3325b37 fixes a stack overflow bug happens when replaying
client requests. Similar stack overflow can happens when processing
finished contexts.

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
mds: fix negative dirstat assertion

When splitting dirfrag, delta dirstat is always added to the first new
dirfrag. Before the delta dirstat is propagated to inode, unlinking file
from the rest dirfrags can cause nagtive inode dirstat.

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
mds: allow sending MMDSFindIno to MDS who is in clientreplay state

Because MDCache::kick_find_ino_peers() is called when a MDS enters
clientreplay state.

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
mds: don't increase nlink when rollback stray reintegration

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
mds: include authority of the overwrited inode in rename witnesses

Rename operation needs to adjust the overwrited inode's link count.

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