Date:   Fri, 15 Jun 2018 18:28:20 -0600
From:   Andreas Dilger <adilger@...ger.ca>
To:     "Luis R. Rodriguez" <mcgrof@...nel.org>
Cc:     Theodore Ts'o <tytso@....edu>, Jan Kara <jack@...e.com>,
        Ext4 Developers List <linux-ext4@...r.kernel.org>,
        Mike Snitzer <snitzer@...hat.com>, hare@...e.de,
        Jens Axboe <axboe@...nel.dk>, mwilck@...e.com,
        Damien Le Moal <damien.lemoal@....com>,
        Bart Van Assche <Bart.VanAssche@....com>
Subject: Re: [PATCH] e2fsprogs: detect zoned disks and prevent their raw use

On Jun 15, 2018, at 2:56 PM, Luis R. Rodriguez <mcgrof@...nel.org> 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 e2fsprogs, 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.ext[234] 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 the
> below was observed with XFS but its expected ext[234] users would see
> the same:

If you are interested in ext4 and SMR drives, there were some patches
developed to allow ext4 to work on zoned disks, essentially converting
it to be a "lazy-journal log-structured" filesystem.  That makes almost
all of the filesystem IO linear (though we could avoid duplicate journal
writes by writing large IOs directly to disk).

This was presented at FAST'17 as "ext4-lazy", though I'm unable to find the
patch that implemented this feature (it is not landed in the kernel yet).

Maybe Ted could send out a URL for the patch, even if it is a WIP?

Cheers, Andreas


> [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 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 ext[234] 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 ext[234].
> 
> 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.ext4
> on a zoned disk, you will now get:
> 
> # mkfs.ext4  /dev/sda
> mke2fs 1.44.2 (14-May-2018)
> /dev/sda: zoned disk detected, refer to dm-zoned-tools for how to use while setting up superblock
> 
> [0] https://lkml.kernel.org/r/20180614001147.1545-1-mcgrof@kernel.org
> 
> Cc: Damien Le Moal <damien.lemoal@....com>
> Cc: Bart Van Assche <Bart.VanAssche@....com>
> Signed-off-by: Luis R. Rodriguez <mcgrof@...nel.org>
> ---
> lib/ext2fs/ext2_err.et.in |  3 +++
> lib/ext2fs/initialize.c   | 30 ++++++++++++++++++++++++++++++
> 2 files changed, 33 insertions(+)
> 
> diff --git a/lib/ext2fs/ext2_err.et.in b/lib/ext2fs/ext2_err.et.in
> index 16abd23d..34ee5793 100644
> --- a/lib/ext2fs/ext2_err.et.in
> +++ b/lib/ext2fs/ext2_err.et.in
> @@ -545,4 +545,7 @@ ec	EXT2_ET_INODE_CORRUPTED,
> ec	EXT2_ET_EA_INODE_CORRUPTED,
> 	"Inode containing extended attribute value is corrupted"
> 
> +ec	EXT2_ET_ZONE_UNSUPPORTED,
> +	"zoned disk detected, refer to dm-zoned-tools for how to use"
> +
> 	end
> diff --git a/lib/ext2fs/initialize.c b/lib/ext2fs/initialize.c
> index dbe798b2..cef8ebb2 100644
> --- a/lib/ext2fs/initialize.c
> +++ b/lib/ext2fs/initialize.c
> @@ -32,6 +32,10 @@
> #define O_BINARY 0
> #endif
> 
> +#ifndef PATH_MAX
> +#define PATH_MAX 1024
> +#endif
> +
> #if defined(__linux__)    &&	defined(EXT2_OS_LINUX)
> #define CREATOR_OS EXT2_OS_LINUX
> #else
> @@ -85,6 +89,28 @@ static unsigned int calc_reserved_gdt_blocks(ext2_filsys fs)
> 	return rsv_gdb;
> }
> 
> +static errcode_t is_zoned_disk(const 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)
> +		return EXT2_ET_INVALID_ARGUMENT;
> +
> +	file = fopen(str, "r");
> +	if (!file)
> +		return 0;
> +
> +	fclose(file);
> +
> +	return EXT2_ET_ZONE_UNSUPPORTED;
> +}
> +
> errcode_t ext2fs_initialize(const char *name, int flags,
> 			    struct ext2_super_block *param,
> 			    io_manager manager, ext2_filsys *ret_fs)
> @@ -112,6 +138,10 @@ errcode_t ext2fs_initialize(const char *name, int flags,
> 	if (!param || !ext2fs_blocks_count(param))
> 		return EXT2_ET_INVALID_ARGUMENT;
> 
> +	retval = is_zoned_disk(name);
> +	if (retval != 0)
> +		return retval;
> +
> 	retval = ext2fs_get_mem(sizeof(struct struct_ext2_filsys), &fs);
> 	if (retval)
> 		return retval;
> --
> 2.17.1
> 


Cheers, Andreas






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