Re: FS (dm-0): device supports 4096 byte sectors (not 512)

From: Johnatan Hallman <johnatan-ftm@protonmail.com>
To: Eric Sandeen <sandeen@sandeen.net>
Cc: "linux-xfs@vger.kernel.org" <linux-xfs@vger.kernel.org>
Subject: Re: FS (dm-0): device supports 4096 byte sectors (not 512)
Date: Thu, 23 Mar 2023 19:00:29 +0000	[thread overview]
Message-ID: <LFK3n9vuD50k0XOFPlxBpqoqZvSp70fNnymLOjCly1olnwRPwhbK0EspfTZAtWgUrju2yOCId64YGDXbVhbe7wz2AZNAOU5_hBTmlHBlhJM=@protonmail.com> (raw)
In-Reply-To: <85a9bb82-864e-5532-9252-f8055baeb790@sandeen.net>

Hello,

It's a single luks encrypted disk, nothing complex is going on. I don't get it either how that changed. 

NAME                MAJ:MIN RM   SIZE RO TYPE  MOUNTPOINT
sda                   8:0    0   3.7T  0 disk  
`-test              254:1    0   3.7T  0 crypt 

There is no problem with the encryption it can be opened. 

test	(254:1)

I have tried to open it like this, same story:

cryptsetup --verbose -b 512 luksOpen /dev/sda test

------- Original Message -------
On Thursday, March 23rd, 2023 at 4:39 PM, Eric Sandeen <sandeen@sandeen.net> wrote:

> On 3/23/23 5:45 AM, Johnatan Hallman wrote:
> 
> > Hello List,
> > 
> > I get this error when I try to mount an XFS partition.
> > Fortunately there is no critical data on it as it is just a backup but I would still like to mount it if it's possible.
> > 
> > I have tried with various Linux distros with kernels ranging from 5.6 to 6.1 it's the same result.
> > 
> > xfs_info /dev/mapper/test
> > meta-data=/dev/mapper/test isize=256 agcount=32, agsize=30523559 blks
> > = sectsz=512 attr=2, projid32bit=0
> > = crc=0 finobt=0, sparse=0, rmapbt=0
> > = reflink=0 bigtime=0 inobtcount=0 nrext64=0
> > data = bsize=4096 blocks=976753869, imaxpct=5
> > = sunit=0 swidth=0 blks
> > naming =version 2 bsize=4096 ascii-ci=0, ftype=0
> > log =internal log bsize=4096 blocks=476930, version=2
> > = sectsz=512 sunit=0 blks, lazy-count=1
> > realtime =none extsz=4096 blocks=0, rtextents=0
> > 
> > mount -t xfs -o ro /dev/mapper/test /mnt/
> > mount: /mnt: mount(2) system call failed: Function not implemented.
> > dmesg(1) may have more information after failed mount system call.
> 
> 
> So I assume dmesg contained the error in $SUBJECT:
> 
> FS (dm-0): device supports 4096 byte sectors (not 512)
> 
> It seems that the filesystem was created with 512-byte sectors - at that time, the device
> must have supported them. Perhaps something about the devicemapper target changed from
> a 512 device to a 4k device? I'm not sure what might cause that to happen, but IMHO
> it should never happen... did the dm device recently get reconfigured?
> 
> As a last resort, I think you could dd the filesystem (all 3T) to a file, and use a
> loopback mount to access the files.
> 
> Alternatively, I wonder if we could relax the sector size check for a read-only
> mount (that does not require log replay) - I'm not sure about that though.
> 
> -Eric