Re: [f2fs-dev] [PATCH v2 3/3] f2fs: fix handling of zoned block devices with max_open_zones == 0

[Jaegeuk Kim via Linux-f2fs-devel <linux-f2fs-devel@lists.sourceforge.net>]

This breaks the device giving 0 open zone which was working. Hence, I dropped
the change.

On 11/10, Yongpeng Yang wrote:
> From: Yongpeng Yang <yangyongpeng@xiaomi.com>
> 
> When emulating a ZNS SSD on qemu with zoned.max_open set to 0, the
> F2FS can still be mounted successfully. The sysfs entry shows
> sbi->max_open_zones as UINT_MAX.
> 
> root@fedora-vm:~# cat /sys/block/nvme0n1/queue/zoned
> host-managed
> root@fedora-vm:~# cat /sys/block/nvme0n1/queue/max_open_zones
> 0
> root@fedora-vm:~# mkfs.f2fs -m -c /dev/nvme0n1 /dev/vda
> root@fedora-vm:~# mount /dev/vda /mnt/f2fs/
> root@fedora-vm:~# cat /sys/fs/f2fs/vda/max_open_zones
> 4294967295
> 
> The root cause is that sbi->max_open_zones is initialized to UINT_MAX
> and only updated when the device’s max_open_zones is greater than 0.
> However, both the scsi driver (sd_zbc_read_zones may assigns 0 to
> device's max_open_zones) and the nvme driver (nvme_query_zone_info don't
> check max_open_zones) allow max_open_zones to be 0.
> 
> This patch fixes the issue by preventing mounting on zoned SSDs when
> max_open_zones is 0, while still allowing SMR HDDs to be mounted.
> init_blkz_info() is only called by f2fs_scan_devices(), and the
> blkzoned feature has already been checked there. So, this patch also
> remove redundant zoned device checks.
> 
> Signed-off-by: Yongpeng Yang <yangyongpeng@xiaomi.com>
> ---
>  fs/f2fs/super.c | 36 +++++++++++++++++++++---------------
>  1 file changed, 21 insertions(+), 15 deletions(-)
> 
> diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
> index db7afb806411..6dc8945e24af 100644
> --- a/fs/f2fs/super.c
> +++ b/fs/f2fs/super.c
> @@ -4353,21 +4353,6 @@ static int init_blkz_info(struct f2fs_sb_info *sbi, int devi)
>  	unsigned int max_open_zones;
>  	int ret;
>  
> -	if (!f2fs_sb_has_blkzoned(sbi))
> -		return 0;
> -
> -	if (bdev_is_zoned(FDEV(devi).bdev)) {
> -		max_open_zones = bdev_max_open_zones(bdev);
> -		if (max_open_zones && (max_open_zones < sbi->max_open_zones))
> -			sbi->max_open_zones = max_open_zones;
> -		if (sbi->max_open_zones < F2FS_OPTION(sbi).active_logs) {
> -			f2fs_err(sbi,
> -				"zoned: max open zones %u is too small, need at least %u open zones",
> -				sbi->max_open_zones, F2FS_OPTION(sbi).active_logs);
> -			return -EINVAL;
> -		}
> -	}
> -
>  	zone_sectors = bdev_zone_sectors(bdev);
>  	if (sbi->blocks_per_blkz && sbi->blocks_per_blkz !=
>  				SECTOR_TO_BLOCK(zone_sectors))
> @@ -4378,6 +4363,27 @@ static int init_blkz_info(struct f2fs_sb_info *sbi, int devi)
>  	if (nr_sectors & (zone_sectors - 1))
>  		FDEV(devi).nr_blkz++;
>  
> +	max_open_zones = bdev_max_open_zones(bdev);
> +	if (!max_open_zones) {
> +		/*
> +		 * SSDs require max_open_zones > 0 to be mountable.
> +		 * For HDDs, if max_open_zones is reported as 0, it doesn't matter,
> +		 * set it to FDEV(devi).nr_blkz.
> +		 */
> +		if (bdev_nonrot(bdev)) {
> +			f2fs_err(sbi, "zoned: SSD device %s without open zones", FDEV(devi).path);
> +			return -EINVAL;
> +		}
> +		max_open_zones = FDEV(devi).nr_blkz;
> +	}
> +	sbi->max_open_zones = min_t(unsigned int, max_open_zones, sbi->max_open_zones);
> +	if (sbi->max_open_zones < F2FS_OPTION(sbi).active_logs) {
> +		f2fs_err(sbi,
> +			"zoned: max open zones %u is too small, need at least %u open zones",
> +			sbi->max_open_zones, F2FS_OPTION(sbi).active_logs);
> +		return -EINVAL;
> +	}
> +
>  	FDEV(devi).blkz_seq = f2fs_kvzalloc(sbi,
>  					BITS_TO_LONGS(FDEV(devi).nr_blkz)
>  					* sizeof(unsigned long),
> -- 
> 2.43.0


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