linux-ext4 - ext4 and dd of emmc

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Date:   Thu, 22 Oct 2020 10:46:18 -0700
From:   Radivoje Jovanovic <radivojejovanovic@...il.com>
To:     linux-ext4@...r.kernel.org
Subject: ext4 and dd of emmc

Hello,
I am creating empty  4GB ext4 partition on emmc with parted like this:
parted -s -a optimal /dev/emmcblk0 mkpart data ext4 1024 5120
mkfs.ext4 /dev/mmcblk0p7 (this is the partition that was created in
the previous step)

I do not mount this partition before I do dd of the emmc.
dd of the emmc is done like this:
dd if=/dev/emmcblk0 | gzip -c | dd of=./image.bin

after this I write back the emmc with the same binary file:
dd if=./image.bin | gunzip -c | dd of=. /dev/emmcblk0

now I boot the system and mount the partition from the emmc.

at the boot the kernel reports:
EXT4-fs (mmcblk0p7): warning: mounting fs with errors, running e2fsck
is recommended

after the system is fully booted I see errors such as:
EXT4-fs error (device mmcblk0p7): ext4_journal_check_start:61:
Detected aborted journal
Buffer I/O error on dev mmcblk0p7, logical block 0, lost sync page write
EXT4-fs (mmcblk0p7): I/O error while writing superblock

All other partitions on the system are ReadOnly so probably that is
why I do not see errors for them

I am running custom Yocto build on this.
the kernel is vanilla 5.4.57 with an additional pci driver we have.

Any idea why this is happening?

Thanks
Ogi