On (24/12/12 00:37), Theodore Ts'o wrote:

The blocks which are getting modified while a write is in flight are
ext4 metadata blocks, which are in the buffer cache.  Ext4 is
modifying those blocks via bh->b_data, and ext4 isn't issuing the
write; those are happenig via the buffer cache's writeback functions.

Hmmm.... was the user using an ext4 file system with the journal
disabled, by any chance?

I believe you are right, at least that's what caiqingfu said [1]:

echo 524288000 > /sys/devices/virtual/block/zram0/disksize
mkfs.ext4 -O ^has_journal -b 4096 -F -L TEMP -m 0 /dev/zram0
mkdir /tmp/zram
mount -t ext4 -o errors=continue,nosuid,nodev,noatime /dev/zram0 /tmp/zram

[1] https://lore.kernel.org/mm-commits/20241202100753.139305-1-baicaiaichibaicai@gmail.com/ (local)