Re: [PATCH v14 03/42] btrfs: defer loading zone info after opening trees

From: Anand Jain <anand.jain@oracle.com>
To: Naohiro Aota <naohiro.aota@wdc.com>,
	linux-btrfs@vger.kernel.org, dsterba@suse.com
Cc: hare@suse.com, linux-fsdevel@vger.kernel.org,
	Jens Axboe <axboe@kernel.dk>,
	Christoph Hellwig <hch@infradead.org>,
	"Darrick J. Wong" <darrick.wong@oracle.com>,
	Josef Bacik <josef@toxicpanda.com>
Subject: Re: [PATCH v14 03/42] btrfs: defer loading zone info after opening trees
Date: Sun, 31 Jan 2021 06:09:48 +0800	[thread overview]
Message-ID: <bfecca45-0a0a-1b00-1e9b-3020577b1f5f@oracle.com> (raw)
In-Reply-To: <d995c6d145d65b93fc1be56d5c5dfab869f50911.1611627788.git.naohiro.aota@wdc.com>

On 1/26/2021 10:24 AM, Naohiro Aota wrote:
> This is preparation patch to implement zone emulation on a regular device.
> 
> To emulate zoned mode on a regular (non-zoned) device, we need to decide an
> emulating zone size. Instead of making it compile-time static value, we'll
> make it configurable at mkfs time. Since we have one zone == one device
> extent restriction, we can determine the emulated zone size from the size
> of a device extent. We can extend btrfs_get_dev_zone_info() to show a
> regular device filled with conventional zones once the zone size is
> decided.
> 
> The current call site of btrfs_get_dev_zone_info() during the mount process
> is earlier than reading the trees, so we can't slice a regular device to
> conventional zones. This patch defers the loading of zone info to
> open_ctree() to load the emulated zone size from a device extent.
> 
> Reviewed-by: Josef Bacik <josef@toxicpanda.com>
> Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>

Patches are already in for-next. My apologies for the delay in review 
here and in the following patches how many ever I could.

Reviewed-by: Anand Jain <anand.jain@oracle.com>

Thanks.

> ---
>   fs/btrfs/disk-io.c | 13 +++++++++++++
>   fs/btrfs/volumes.c |  4 ----
>   fs/btrfs/zoned.c   | 24 ++++++++++++++++++++++++
>   fs/btrfs/zoned.h   |  7 +++++++
>   4 files changed, 44 insertions(+), 4 deletions(-)
> 
> diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
> index 5473bed6a7e8..39cbe10a81b6 100644
> --- a/fs/btrfs/disk-io.c
> +++ b/fs/btrfs/disk-io.c
> @@ -3257,6 +3257,19 @@ int __cold open_ctree(struct super_block *sb, struct btrfs_fs_devices *fs_device
>   	if (ret)
>   		goto fail_tree_roots;
>   
> +	/*
> +	 * Get zone type information of zoned block devices. This will also
> +	 * handle emulation of the zoned mode for btrfs if a regular device has
> +	 * the zoned incompat feature flag set.
> +	 */
> +	ret = btrfs_get_dev_zone_info_all_devices(fs_info);
> +	if (ret) {
> +		btrfs_err(fs_info,
> +			  "failed to read device zone info: %d",
> +			  ret);
> +		goto fail_block_groups;
> +	}
> +
>   	/*
>   	 * If we have a uuid root and we're not being told to rescan we need to
>   	 * check the generation here so we can set the
> diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
> index badb972919eb..bb3f341f6a22 100644
> --- a/fs/btrfs/volumes.c
> +++ b/fs/btrfs/volumes.c
> @@ -669,10 +669,6 @@ static int btrfs_open_one_device(struct btrfs_fs_devices *fs_devices,
>   	clear_bit(BTRFS_DEV_STATE_IN_FS_METADATA, &device->dev_state);
>   	device->mode = flags;
>   
> -	ret = btrfs_get_dev_zone_info(device);
> -	if (ret != 0)
> -		goto error_free_page;
> -
>   	fs_devices->open_devices++;
>   	if (test_bit(BTRFS_DEV_STATE_WRITEABLE, &device->dev_state) &&
>   	    device->devid != BTRFS_DEV_REPLACE_DEVID) {
> diff --git a/fs/btrfs/zoned.c b/fs/btrfs/zoned.c
> index c38846659019..bcabdb2c97f1 100644
> --- a/fs/btrfs/zoned.c
> +++ b/fs/btrfs/zoned.c
> @@ -143,6 +143,30 @@ static int btrfs_get_dev_zones(struct btrfs_device *device, u64 pos,
>   	return 0;
>   }
>   
> +int btrfs_get_dev_zone_info_all_devices(struct btrfs_fs_info *fs_info)
> +{
> +	struct btrfs_fs_devices *fs_devices = fs_info->fs_devices;
> +	struct btrfs_device *device;
> +	int ret = 0;
> +
> +	if (!btrfs_fs_incompat(fs_info, ZONED))
> +		return 0;
> +
> +	mutex_lock(&fs_devices->device_list_mutex);
> +	list_for_each_entry(device, &fs_devices->devices, dev_list) {
> +		/* We can skip reading of zone info for missing devices */
> +		if (!device->bdev)
> +			continue;
> +
> +		ret = btrfs_get_dev_zone_info(device);
> +		if (ret)
> +			break;
> +	}
> +	mutex_unlock(&fs_devices->device_list_mutex);
> +
> +	return ret;
> +}
> +
>   int btrfs_get_dev_zone_info(struct btrfs_device *device)
>   {
>   	struct btrfs_zoned_device_info *zone_info = NULL;
> diff --git a/fs/btrfs/zoned.h b/fs/btrfs/zoned.h
> index 8abe2f83272b..5e0e7de84a82 100644
> --- a/fs/btrfs/zoned.h
> +++ b/fs/btrfs/zoned.h
> @@ -25,6 +25,7 @@ struct btrfs_zoned_device_info {
>   #ifdef CONFIG_BLK_DEV_ZONED
>   int btrfs_get_dev_zone(struct btrfs_device *device, u64 pos,
>   		       struct blk_zone *zone);
> +int btrfs_get_dev_zone_info_all_devices(struct btrfs_fs_info *fs_info);
>   int btrfs_get_dev_zone_info(struct btrfs_device *device);
>   void btrfs_destroy_dev_zone_info(struct btrfs_device *device);
>   int btrfs_check_zoned_mode(struct btrfs_fs_info *fs_info);
> @@ -42,6 +43,12 @@ static inline int btrfs_get_dev_zone(struct btrfs_device *device, u64 pos,
>   	return 0;
>   }
>   
> +static inline int btrfs_get_dev_zone_info_all_devices(
> +	struct btrfs_fs_info *fs_info)
> +{
> +	return 0;
> +}
> +
>   static inline int btrfs_get_dev_zone_info(struct btrfs_device *device)
>   {
>   	return 0;
> 