Chinese MSM8916 Device, "Could not mount system partition" Error in TWRP - Android Q&A, Help & Troubleshooting

Could not mount system partition.
Hi All,
I need some help, I'm building my own TWRP for my own device. It's a Chinese custom phone running msm8916, 1GO Ram and 8Go of storage.
My TWRP boots fine, adb shell prompt me a nice root shell, I have no error in dmesg or recovery logs
yet when SuperSu or I try to mount the system partition as RW it doesn't work. It's always mounted as RO (I use plain mount command to check)
I tried a lots of command including
Code:
#mount -o remount,rw -t ext4 /dev/block/bootdevice/by-name/system /system
#mount -o remount,rw /system
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I don't have the kernel source code and use a prebuilt kernel extracted from the bootimage.
You can find my code here : github com/supercairos/android_device_doro_hero
If you have any idea why this is happening I would be very glad!
Best,
R.

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When looking a dmesg it outputs :
<6>[ 14.757619] EXT4-fs (mmcblk0p22): mounted filesystem with ordered data mod
e. Opts: (null)
<7>[ 14.757638] SELinux: initialized (dev mmcblk0p22, type ext4), uses xattr
<3>[ 16.049825] mmc0: sdhci_cmd_irq: AUTO CMD err sts 0x00000002
<3>[ 16.049946] mmcblk0: timed out sending r/w cmd command, card status 0x400d
00
<3>[ 16.049951] mmcblk0: command error, retrying timeout
<3>[ 21.069858] mmc0: sdhci_cmd_irq: AUTO CMD err sts 0x00000002
<3>[ 21.069916] mmcblk0: timed out sending r/w cmd command, card status 0x400d
00
<3>[ 21.069921] mmcblk0: command error, retrying timeout
<3>[ 21.070127] mmc0: cache flush timeout
<3>[ 21.070153] mmc0: mmc_interrupt_hpi() failed (-22)
<3>[ 21.070158] mmcblk0: mmc_blk_issue_flush: restart mmc card
<3>[ 21.097327] mmcblk0: mmc_blk_issue_flush: notify flush error to upper laye
rs<3>[ 21.097337] end_request: I/O error, dev mmcblk0, sector 407568
<3>[ 21.097356] Aborting journal on device mmcblk0p22-8.
<3>[ 21.107997] mmc0: sdhci_cmd_irq: AUTO CMD err sts 0x00000002
<3>[ 21.108062] mmcblk0: timed out sending r/w cmd command, card status 0x400d
00
<3>[ 21.108067] mmcblk0: command error, retrying timeout
<2>[ 21.108167] EXT4-fs error (device mmcblk0p22): __ext4_journal_start_sb:62:
Detected aborted journal
<2>[ 21.108175] EXT4-fs (mmcblk0p22): Remounting filesystem read-only
<3>[ 21.108228] mmc0: sdhci_cmd_irq: AUTO CMD err sts 0x00000002
<3>[ 21.108295] mmcblk0: timed out sending r/w cmd command, card status 0x400d
00
<3>[ 21.108300] mmcblk0: command error, retrying timeout
<3>[ 31.138023] mmc0:cache disable operation timeout
<3>[ 31.138059] mmc0: mmc_interrupt_hpi() failed (-22)
<3>[ 31.138074] mmc0: mmc_host_runtime_suspend: suspend host failed: -110
<3>[ 34.268118] mmc0: sdhci_cmd_irq: AUTO CMD err sts 0x00000002
<3>[ 34.268201] mmcblk0: timed out sending r/w cmd command, card status 0x400d
00
<3>[ 34.268207] mmcblk0: command error, retrying timeout
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