btrfs: zoned: implement zoned chunk allocator
Implement a zoned chunk and device extent allocator. One device zone becomes a device extent so that a zone reset affects only this device extent and does not change the state of blocks in the neighbor device extents. To implement the allocator, we need to extend the following functions for a zoned filesystem. - init_alloc_chunk_ctl - dev_extent_search_start - dev_extent_hole_check - decide_stripe_size init_alloc_chunk_ctl_zoned() is mostly the same as regular one. It always set the stripe_size to the zone size and aligns the parameters to the zone size. dev_extent_search_start() only aligns the start offset to zone boundaries. We don't care about the first 1MB like in regular filesystem because we anyway reserve the first two zones for superblock logging. dev_extent_hole_check_zoned() checks if zones in given hole are either conventional or empty sequential zones. Also, it skips zones reserved for superblock logging. With the change to the hole, the new hole may now contain pending extents. So, in this case, loop again to check that. Finally, decide_stripe_size_zoned() should shrink the number of devices instead of stripe size because we need to honor stripe_size == zone_size. Reviewed-by: Anand Jain <anand.jain@oracle.com> Reviewed-by: Josef Bacik <josef@toxicpanda.com> Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
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