Re: [PATCH] libxfs: detect zoned disks and prevent their raw use

["Darrick J. Wong" <darrick.wong@oracle.com>]

On Fri, Jun 15, 2018 at 01:50:11PM -0700, Luis R. Rodriguez wrote:
> Using raw zoned disks by filesystems requires special handling, only
> f2fs currently supports this. All other filesystems do not support
> dealing with zoned disks directly.
> 
> As such using raw zoned disks is not supported by XFS, to use them you
> need to use dm-zoned-tools, format them with dzadm, set the scheduler to
> deadline, and then setup a dmsetup with zoned type, and somehow set
> this up on every boot to live a semi-happy life for now.
> 
> Even if you use dmsetup on every boot, the zoned disk is still exposed,
> and a user may still think they have to run mkfs.xfs on it instead
> of the /dev/mapper/ disk, and then mount it by mistake.
> 
> In either case you may seem to believe your disk works and only eventually
> end up with alignmet issues and perhaps lose you data. For instance:
> 
> [10869.959501] device-mapper: zoned reclaim: (sda): Align zone 865 wp 28349 to 30842 (wp+2493) blocks failed -5
> [10870.014488] sd 0:0:0:0: [sda] tag#0 FAILED Result: hostbyte=DID_OK driverbyte=DRIVER_SENSE
> [10870.016137] sd 0:0:0:0: [sda] tag#0 Sense Key : Illegal Request [current]
> [10870.017696] sd 0:0:0:0: [sda] tag#0 Add. Sense: Unaligned write command
> 
> We have to prevent these mistakes by avoiding mkfs.xfs use on zoned disks.
> 
> Note that this not enough yet, if users are on old AHCI controllers,
> the disks may not be detected as zoned. More work through udev may be
> required to detect this situation old old parent PCI IDs for zoned
> disks, and then prevent their use somehow.
> 
> If you are stuck on using XFS there a udev rule out there [0], this is
> far from perfect, and not fully what we want done upstream on Linux
> distributions long term but it should at least help developers for now
> enjoy their shiny big fat zoned disks with XFS.
> 
> This check should help avoid having folks shoot themselves in the foot
> for now with zoned disks. If you make the mistake to use mkfs.xfs
> on a zoned disk, you will now get:
> 
>  # mkfs.xfs /dev/sda
> /dev/sda: zoned disk detected, refer to dm-zoned-tools for how to use with XFS
> 
> [0] https://lkml.kernel.org/r/20180614001147.1545-1-mcgrof@kernel.org
> 
> Cc: Damien Le Moal <damien.lemoal@wdc.com>
> Cc: Bart Van Assche <Bart.VanAssche@wdc.com>
> Signed-off-by: Luis R. Rodriguez <mcgrof@kernel.org>
> ---
>  libxfs/init.c | 41 +++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 41 insertions(+)
> 
> diff --git a/libxfs/init.c b/libxfs/init.c
> index a65c86c3..cca33ec7 100644
> --- a/libxfs/init.c
> +++ b/libxfs/init.c
> @@ -98,6 +98,32 @@ libxfs_device_to_fd(dev_t device)
>  	/* NOTREACHED */
>  }
>  
> +static int
> +is_zoned_disk(char *path)
> +{
> +	char str[PATH_MAX];
> +	char *devname = basename(path);
> +	FILE *file;
> +	int len;
> +
> +
> +	len = snprintf(str, sizeof(str), "/sys/block/%s/queue/zoned", devname);
> +
> +	/* Indicates truncation */
> +	if (len >= PATH_MAX) {
> +		errno = ENAMETOOLONG;
> +		return -1;
> +	}
> +
> +	file = fopen(str, "r");
> +	if (!file)
> +		return 0;
> +

Shouldn't we read the *file contents and return 0 if the contents
are 'none'?

$ lsscsi
[0:0:0:0]    disk    ATA      Samsung SSD 850  1B6Q  /dev/sda
$ cat /sys/block/sda/queue/zoned
none

--D

> +	fclose(file);
> +
> +	return 1;
> +}
> +
>  /* libxfs_device_open:
>   *     open a device and return its device number
>   */
> @@ -108,6 +134,7 @@ libxfs_device_open(char *path, int creat, int xflags, int setblksize)
>  	int		fd, d, flags;
>  	int		readonly, dio, excl;
>  	struct stat	statb;
> +	int ret;
>  
>  	readonly = (xflags & LIBXFS_ISREADONLY);
>  	excl = (xflags & LIBXFS_EXCLUSIVELY) && !creat;
> @@ -119,6 +146,20 @@ retry:
>  		(dio ? O_DIRECT : 0) | \
>  		(excl ? O_EXCL : 0);
>  
> +	ret = is_zoned_disk(path);
> +	if (ret < 0) {
> +		fprintf(stderr, _("%s: error opening %s\n"),
> +			path, strerror(errno));
> +		exit(1);
> +	}
> +
> +	if (ret == 1) {
> +		fprintf(stderr,
> +_("%s: zoned disk detected, refer to dm-zoned-tools for how to use with XFS\n"),
> +			path);
> +		exit(1);
> +	}
> +
>  	if ((fd = open(path, flags, 0666)) < 0) {
>  		if (errno == EINVAL && --dio == 0)
>  			goto retry;
> -- 
> 2.17.1
> 
> --
> To unsubscribe from this list: send the line "unsubscribe linux-xfs" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html