xfs: fix realtime bitmap/summary file truncation when growing rt volume

xfs: fix realtime bitmap/summary file truncation when growing rt volume

The realtime bitmap and summary files are regular files that are hidden
away from the directory tree.  Since they're regular files, inode
inactivation will try to purge what it thinks are speculative
preallocations beyond the incore size of the file.  Unfortunately,
xfs_growfs_rt forgets to update the incore size when it resizes the
inodes, with the result that inactivating the rt inodes at unmount time
will cause their contents to be truncated.

Fix this by updating the incore size when we change the ondisk size as
part of updating the superblock.  Note that we don't do this when we're
allocating blocks to the rt inodes because we actually want those blocks
to get purged if the growfs fails.

This fixes corruption complaints from the online rtsummary checker when
running xfs/233.  Since that test requires rmap, one can also trigger
this by growing an rt volume, cycling the mount, and creating rt files.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Chandan Babu R <chandanrlinux@gmail.com>