Re: [PATCH] f2fs: Reduce zoned block device memory usage

[Christoph Hellwig <hch@infradead.org>]

On Tue, Feb 20, 2018 at 03:06:10PM +0900, Damien Le Moal wrote:
> For a zoned block device mount, an array of zone types for the device is
> allocated and initialized in order to determine if a section is stored
> on a sequential zone (zone reset needed) or a conventional zone (no zone
> reset needed and regular discard applies). Considering this usage, the
> zone types stored in memory can be replaced with a bitmap to indicate
> equivalent information, that is, if a zone is sequential or not. This
> reduces the memory usage for the device mount by roughly 8 (on a 14TB
> disk with zones of 256 MB, the zone type array consumes 13x4KB pages
> while the bitmap uses only 2x4KB pages.
> 
> This patch changes the f2fs_dev_info structure blkz_type field to the
> bitmap blkz_seq. Access to this bitmap is done using the function
> f2fs_blkz_is_seq(), which is a rewrite of the function get_blkz_type().

Is there any way we could just provide a block layer helper to
figure this out so that the file system code could be simplified even
more?