Re: [PATCH for-5.15.y] btrfs: zoned: cache reported zone during mount

[Greg KH <greg@kroah.com>]

On Thu, Feb 17, 2022 at 01:50:56PM +0900, Naohiro Aota wrote:
> commit 16beac87e95e2fb278b552397c8260637f8a63f7 upstream.
> 
> When mounting a device, we are reporting the zones twice: once for
> checking the zone attributes in btrfs_get_dev_zone_info and once for
> loading block groups' zone info in
> btrfs_load_block_group_zone_info(). With a lot of block groups, that
> leads to a lot of REPORT ZONE commands and slows down the mount
> process.
> 
> This patch introduces a zone info cache in struct
> btrfs_zoned_device_info. The cache is populated while in
> btrfs_get_dev_zone_info() and used for
> btrfs_load_block_group_zone_info() to reduce the number of REPORT ZONE
> commands. The zone cache is then released after loading the block
> groups, as it will not be much effective during the run time.
> 
> Benchmark: Mount an HDD with 57,007 block groups
> Before patch: 171.368 seconds
> After patch: 64.064 seconds
> 
> While it still takes a minute due to the slowness of loading all the
> block groups, the patch reduces the mount time by 1/3.
> 
> Link: https://lore.kernel.org/linux-btrfs/CAHQ7scUiLtcTqZOMMY5kbWUBOhGRwKo6J6wYPT5WY+C=cD49nQ@mail.gmail.com/
> Fixes: 5b316468983d ("btrfs: get zone information of zoned block devices")
> CC: stable@vger.kernel.org
> Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
> Signed-off-by: David Sterba <dsterba@suse.com>
> ---
>  fs/btrfs/dev-replace.c |  2 +-
>  fs/btrfs/disk-io.c     |  2 +
>  fs/btrfs/volumes.c     |  2 +-
>  fs/btrfs/zoned.c       | 85 ++++++++++++++++++++++++++++++++++++++----
>  fs/btrfs/zoned.h       |  8 +++-
>  5 files changed, 87 insertions(+), 12 deletions(-)

Now queued up, thanks.

greg k-h