zonefs: add zone-capacity support

In the zoned storage model, the sectors within a zone are typically all
writeable. With the introduction of the Zoned Namespace (ZNS) Command
Set in the NVM Express organization, the model was extended to have a
specific writeable capacity.

This zone capacity can be less than the overall zone size for a NVMe ZNS
device or null_blk in zoned-mode. For other ZBC/ZAC devices the zone
capacity is always equal to the zone size.

Use the zone capacity field instead from blk_zone for determining the
maximum inode size and inode blocks in zonefs.

Signed-off-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>

fs/zonefs/zonefs.h

@@ -56,6 +56,9 @@ struct zonefs_inode_info {
 	/* File maximum size */
 	loff_t			i_max_size;
 
+	/* File zone size */
+	loff_t			i_zone_size;
+
 	/*
 	 * To serialise fully against both syscall and mmap based IO and
 	 * sequential file truncation, two locks are used. For serializing