xfs: make tr_growdata a permanent transaction

xfs: make tr_growdata a permanent transaction

The growdata transaction is used by growfs operations to increase
the data size of the filesystem. Part of this sequence involves
extending the size of the last preexisting AG in the fs, if
necessary. This is implemented by freeing the newly available
physical range to the AG.

tr_growdata is not a permanent transaction, however, and block
allocation transactions must be permanent to handle deferred frees
of AGFL blocks. If the grow operation extends an existing AG that
requires AGFL fixing, assert failures occur due to a populated dfops
list on a non-permanent transaction and the AGFL free does not
occur. This is reproduced (rarely) by xfs/104.

Change tr_growdata to a permanent transaction with a default log
count. This increases initial transaction reservation size, but
growfs is an infrequent and non-performance critical operation and
so should have minimal impact.

Reported-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
[darrick: add a comment to the assert]
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>