linux-ext4 - Re: ext4: failed to convert unwritten extents (6.12.31 regression)

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Message-Id: <8F227773-BD56-4E6F-BB6A-F24931186D77@dilger.ca>
Date: Mon, 22 Sep 2025 14:51:52 -0600
From: Andreas Dilger <adilger@...ger.ca>
To: Andrea Biardi <Andrea.Biardi@...visolutions.com>
Cc: Theodore Ts'o <tytso@....edu>,
 linux-ext4 <linux-ext4@...r.kernel.org>
Subject: Re: ext4: failed to convert unwritten extents (6.12.31 regression)

On Sep 22, 2025, at 8:00 AM, Andrea Biardi <Andrea.Biardi@...visolutions.com> wrote:
> 
> On 22-Sep-2025,  "Theodore Ts'o" <tytso@....edu> wrote:
> 
>>> [  174.903010] I/O error, dev vda, sector 167922 op 0x1:(WRITE) flags 0x0 phys_seg 2 prio class 0
>>> [  174.903023] I/O error, dev vda, sector 167938 op 0x1:(WRITE) flags 0x4000 phys_seg 254 prio class 0
>>> [  174.903027] I/O error, dev vda, sector 169970 op 0x1:(WRITE) flags 0x0 phys_seg 2 prio class 0
>>> [  174.903031] EXT4-fs warning (device vda1): ext4_end_bio:353: I/O error 10 writing to inode 16 starting block 84985)
>> 
>> The failure is coming from the block device, which in your case, is
>> the virtio device.  The only causes for this are:
>> 1)  An underlying hardware failure
>> 2)  A bug in the block virtio device
>> 3)  A bug in the VMM (I assume qemu in your case).
> 
> Thank you for the quick response!
> 
> You do have a point there, the first reported problem is effectively a write failure on vda.
> I tried with virtio-scsi, and can't reproduce the bug. I will try with a newer version of qemu first, and then look into virtio-blk.

It _could_ still be a software issue, if these vda errors are caused by writes
beyond the end of the block device?  These are showing errors at sector 167922+
so if the vda=/boot filesystem is just below 82MiB=83968 blocks=167936 sectors
in size then this might be the issue?

If adding/removing this specific patch shows/hides this patch then it could
also be a bug in how the ext4 extents or uninitialized extent zeroing at the
end of the device is handled, assuming that the /boot device is indeed 82MB.

Have you tried doing a linear read/write of /dev/vda in 1KiB units to confirm
that all of the sectors can be read and written?

It might also be a mismatch between /dev/vda size vs. how many block the
filesystem is formatted to use?

Cheers, Andreas

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