xfs: handle too many open zones when mounting

xfs: handle too many open zones when mounting

When running on conventional zones or devices, the zoned allocator does
not have a real write pointer, but instead fakes it up at mount time
based on the last block recorded in the rmap.  This can create spurious
"open" zones when the last written blocks in a conventional zone are
invalidated.  Add a loop to the mount code to find the conventional zone
with the highest used block in the rmap tree and "finish" it until we
are below the open zones limit.

While we're at it, also error out if there are too many open sequential
zones, which can only happen when the user overrode the max open zones
limit (or with really buggy hardware reducing the limit, but not much
we can do about that).

Fixes: 4e4d52075577 ("xfs: add the zoned space allocator")
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Hans Holmberg <hans.holmberg@wdc.com>
Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
Signed-off-by: Carlos Maiolino <cem@kernel.org>