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Subject: Re: [RFC PATCH 03/17] btrfs: Check and enable HMZONED mode
To:     Naohiro Aota <naota@elisp.net>, David Sterba <dsterba@suse.com>,
        linux-btrfs@vger.kernel.org
Cc:     Chris Mason <clm@fb.com>, Josef Bacik <jbacik@fb.com>,
        linux-kernel@vger.kernel.org,
        Damien Le Moal <damien.lemoal@wdc.com>,
        Bart Van Assche <bart.vanassche@wdc.com>,
        Matias Bjorling <mb@lightnvm.io>
References: <20180809180450.5091-1-naota@elisp.net>
 <20180809180450.5091-4-naota@elisp.net>
From:   Hannes Reinecke <hare@suse.com>
Message-ID: <51ed0d0b-7574-b9a9-bae5-2cc8042913e6@suse.com>
Date:   Fri, 10 Aug 2018 14:25:33 +0200
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On 08/09/2018 08:04 PM, Naohiro Aota wrote:
> HMZONED mode cannot be used together with the RAID5/6 profile. 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 <naota@elisp.net>
> ---
>  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     | 87 ++++++++++++++++++++++++++++++++++++++++++
>  fs/btrfs/volumes.h     |  1 +
>  6 files changed, 112 insertions(+), 5 deletions(-)
> 
> diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
> index 66f1d3895bca..14f880126532 100644
> --- a/fs/btrfs/ctree.h
> +++ b/fs/btrfs/ctree.h
> @@ -763,6 +763,9 @@ 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 dec01970d8c5..839a35008fd8 100644
> --- a/fs/btrfs/dev-replace.c
> +++ b/fs/btrfs/dev-replace.c
> @@ -202,6 +202,13 @@ 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))) {
> +		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 5124c15705ce..14f284382ba7 100644
> --- a/fs/btrfs/disk-io.c
> +++ b/fs/btrfs/disk-io.c
> @@ -3057,6 +3057,13 @@ 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 5fdd95e3de05..cc812e459197 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);
> +	}
>  
>  	/*
>  	 * Even the options are empty, we still need to do extra check
> diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
> index 35b3a2187653..ba7ebb80de4d 100644
> --- a/fs/btrfs/volumes.c
> +++ b/fs/btrfs/volumes.c
> @@ -1293,6 +1293,80 @@ int btrfs_open_devices(struct btrfs_fs_devices *fs_devices,
>  	return ret;
>  }
>  
> +int btrfs_check_hmzoned_mode(struct btrfs_fs_info *fs_info)
> +{
> +	struct btrfs_fs_devices *fs_devices = fs_info->fs_devices;
> +	struct btrfs_device *device;
> +	u64 hmzoned_devices = 0;
> +	u64 nr_devices = 0;
> +	u64 zone_size = 0;
> +	int incompat_hmzoned = btrfs_fs_incompat(fs_info, HMZONED);
> +	int ret = 0;
> +
> +	/* Count zoned devices */
> +	list_for_each_entry(device, &fs_devices->devices, dev_list) {
> +		if (!device->bdev)
> +			continue;
> +		if (bdev_zoned_model(device->bdev) == BLK_ZONED_HM ||
> +		    (bdev_zoned_model(device->bdev) == BLK_ZONED_HA &&
> +		     incompat_hmzoned)) {
> +			hmzoned_devices++;
> +			if (!zone_size) {
> +				zone_size = device->zone_size;
> +			} else if (device->zone_size != zone_size) {
> +				btrfs_err(fs_info,
> +					  "Zoned block devices must have equal zone sizes");
> +				ret = -EINVAL;
> +				goto out;
> +			}
> +		}
> +		nr_devices++;
> +	}
> +
> +	if (!hmzoned_devices && incompat_hmzoned) {
> +		/* No zoned block device, disable HMZONED */
> +		btrfs_err(fs_info, "HMZONED enabled file system should have zoned devices");
> +		ret = -EINVAL;
> +		goto out;
> +	}
> +
> +	fs_info->zone_size = zone_size;
> +
> +	if (hmzoned_devices != nr_devices) {
> +		btrfs_err(fs_info,
> +			  "zoned devices mixed with regular devices");
> +		ret = -EINVAL;
> +		goto out;
> +	}
> +
This breaks existing setups; as we're not checking if the device
specified by fs_info is a zoned device we'll fail here for normal devices.

You need this patch to fix it:

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 43eaf0142062..8609776c9a9e 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -1314,6 +1314,9 @@ int btrfs_check_hmzoned_mode(struct btrfs_fs_info
*fs_info)
        int incompat_hmzoned = btrfs_fs_incompat(fs_info, HMZONED);
        int ret = 0;

+       if (!incompat_hmzoned)
+               return 0;
+
        /* Count zoned devices */
        list_for_each_entry(device, &fs_devices->devices, dev_list) {
                if (!device->bdev)


Cheers,

Hannes
-- 
Dr. Hannes Reinecke		               zSeries & Storage
hare@suse.com			               +49 911 74053 688
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