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Date:   Thu, 13 Jun 2019 09:57:11 -0400
From:   Josef Bacik <josef@toxicpanda.com>
To:     Naohiro Aota <naohiro.aota@wdc.com>
Cc:     linux-btrfs@vger.kernel.org, David Sterba <dsterba@suse.com>,
        Chris Mason <clm@fb.com>, Josef Bacik <josef@toxicpanda.com>,
        Qu Wenruo <wqu@suse.com>, Nikolay Borisov <nborisov@suse.com>,
        linux-kernel@vger.kernel.org, Hannes Reinecke <hare@suse.com>,
        linux-fsdevel@vger.kernel.org,
        Damien Le Moal <damien.lemoal@wdc.com>,
        Matias =?utf-8?B?QmrDuHJsaW5n?= <mb@lightnvm.io>,
        Johannes Thumshirn <jthumshirn@suse.de>,
        Bart Van Assche <bvanassche@acm.org>
Subject: Re: [PATCH 03/19] btrfs: Check and enable HMZONED mode
Message-ID: <20190613135710.nu5r5bpcwdm4we2w@MacBook-Pro-91.local>
References: <20190607131025.31996-1-naohiro.aota@wdc.com>
 <20190607131025.31996-4-naohiro.aota@wdc.com>
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On Fri, Jun 07, 2019 at 10:10:09PM +0900, Naohiro Aota wrote:
> HMZONED mode cannot be used together with the RAID5/6 profile for now.
> Introduce the function btrfs_check_hmzoned_mode() to check this. This
> function will also check if HMZONED flag is enabled on the file system and
> if the file system consists of zoned devices with equal zone size.
> 
> Additionally, as updates to the space cache are in-place, the space cache
> cannot be located over sequential zones and there is no guarantees that the
> device will have enough conventional zones to store this cache. Resolve
> this problem by disabling completely the space cache.  This does not
> introduces any problems with sequential block groups: all the free space is
> located after the allocation pointer and no free space before the pointer.
> There is no need to have such cache.
> 
> Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
> Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
> ---
>  fs/btrfs/ctree.h       |  3 ++
>  fs/btrfs/dev-replace.c |  7 +++
>  fs/btrfs/disk-io.c     |  7 +++
>  fs/btrfs/super.c       | 12 ++---
>  fs/btrfs/volumes.c     | 99 ++++++++++++++++++++++++++++++++++++++++++
>  fs/btrfs/volumes.h     |  1 +
>  6 files changed, 124 insertions(+), 5 deletions(-)
> 
> diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
> index b81c331b28fa..6c00101407e4 100644
> --- a/fs/btrfs/ctree.h
> +++ b/fs/btrfs/ctree.h
> @@ -806,6 +806,9 @@ struct btrfs_fs_info {
>  	struct btrfs_root *uuid_root;
>  	struct btrfs_root *free_space_root;
>  
> +	/* Zone size when in HMZONED mode */
> +	u64 zone_size;
> +
>  	/* the log root tree is a directory of all the other log roots */
>  	struct btrfs_root *log_root_tree;
>  
> diff --git a/fs/btrfs/dev-replace.c b/fs/btrfs/dev-replace.c
> index ee0989c7e3a9..fbe5ea2a04ed 100644
> --- a/fs/btrfs/dev-replace.c
> +++ b/fs/btrfs/dev-replace.c
> @@ -201,6 +201,13 @@ static int btrfs_init_dev_replace_tgtdev(struct btrfs_fs_info *fs_info,
>  		return PTR_ERR(bdev);
>  	}
>  
> +	if ((bdev_zoned_model(bdev) == BLK_ZONED_HM &&
> +	     !btrfs_fs_incompat(fs_info, HMZONED)) ||
> +	    (!bdev_is_zoned(bdev) && btrfs_fs_incompat(fs_info, HMZONED))) {

You do this in a few places, turn this into a helper please.

> +		ret = -EINVAL;
> +		goto error;
> +	}
> +
>  	filemap_write_and_wait(bdev->bd_inode->i_mapping);
>  
>  	devices = &fs_info->fs_devices->devices;
> diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
> index 663efce22d98..7c1404c76768 100644
> --- a/fs/btrfs/disk-io.c
> +++ b/fs/btrfs/disk-io.c
> @@ -3086,6 +3086,13 @@ int open_ctree(struct super_block *sb,
>  
>  	btrfs_free_extra_devids(fs_devices, 1);
>  
> +	ret = btrfs_check_hmzoned_mode(fs_info);
> +	if (ret) {
> +		btrfs_err(fs_info, "failed to init hmzoned mode: %d",
> +				ret);
> +		goto fail_block_groups;
> +	}
> +
>  	ret = btrfs_sysfs_add_fsid(fs_devices, NULL);
>  	if (ret) {
>  		btrfs_err(fs_info, "failed to init sysfs fsid interface: %d",
> diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
> index 2c66d9ea6a3b..740a701f16c5 100644
> --- a/fs/btrfs/super.c
> +++ b/fs/btrfs/super.c
> @@ -435,11 +435,13 @@ int btrfs_parse_options(struct btrfs_fs_info *info, char *options,
>  	bool saved_compress_force;
>  	int no_compress = 0;
>  
> -	cache_gen = btrfs_super_cache_generation(info->super_copy);
> -	if (btrfs_fs_compat_ro(info, FREE_SPACE_TREE))
> -		btrfs_set_opt(info->mount_opt, FREE_SPACE_TREE);
> -	else if (cache_gen)
> -		btrfs_set_opt(info->mount_opt, SPACE_CACHE);
> +	if (!btrfs_fs_incompat(info, HMZONED)) {
> +		cache_gen = btrfs_super_cache_generation(info->super_copy);
> +		if (btrfs_fs_compat_ro(info, FREE_SPACE_TREE))
> +			btrfs_set_opt(info->mount_opt, FREE_SPACE_TREE);
> +		else if (cache_gen)
> +			btrfs_set_opt(info->mount_opt, SPACE_CACHE);
> +	}
>  

This disables the free space tree as well as the cache, sounds like you only
need to disable the free space cache?  Thanks,

Josef