xfs: various fixes for 6.2

This is an assorted collection of bug fixes that have been bundled
together.  The first patch fixes a metadump corruption vector resulting
from a three-way race between a slow-running blkid process, the kernel
mounting, changing, and unmounting the fs, and xfs_db reading stale
block device pagecache contents.

The middle two patches address gcc warnings.

The final patch fixes a subtle corruption bug wherein making a delalloc
reservation on a filesystem with quotas enabled would sample the data
mapping, try to attach dquots, unlock the inode to attach the dquots,
relock the inode, and fail to reverify the sampled data.  If another
process updated the data mapping while the inode was unlocked, the
reservation would proceed with stale data and corrupt the data fork.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
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