[Nexus 7 Q&A, Help & Troubleshooting] XMChrizzz:
I have a strange problem with my 8GB Nexus 7 and I hope, its not a hardware fault.

I buyed the Tablet in 08/2012 at googles playstore and installed CWM Recovery.

After Updating to Android 4.2 at 11/2012, the Tablet works 2 days without any Problems.

After a restart (battery was empty), the Tablet boots and stops at a screen for unlocking encrypted storage. It asks for a password.

Because i never entered a password, and never encrypt the Tablet, i try a wipe at CWM. It ends with an error message:

-- wiping data

Formatting /data

Error mounting /data

...

So i checked dmesg at ADB (cutted, full LOG is attached):

<6>[ 0.000000] Initializing cgroup subsys cpu
<5>[ 0.000000] Linux version 3.1.10-g52027f9 (android-build@vpbs1.mtv.corp.google.com) (gcc version 4.6.x-google 20120106 (prerelease) (GCC) ) #1 SMP PREEMPT Thu Jun 28 16:19:26 PDT 2012
<6>[ 7.684297] mmc1: new high speed SDIO card at address 0001
<6>[ 7.691530] [mmc]:mmc_rescan_try_freq:1892 mmc1: sdio completed
<6>[ 9.020863] EXT4-fs (mmcblk0p4): recovery complete
<6>[ 9.021726] EXT4-fs (mmcblk0p4): mounted filesystem with ordered data mode. Opts:
<6>[ 9.070219] cable_detection_work_handler(): vbus_active = 0 and is_active = 1
<6>[ 9.070227] The USB cable is connected
<3>[ 9.088156] mmcblk0: error -110 transferring data, sector 1391352, nr 64, cmd response 0x900, card status 0x4000d00
<3>[ 9.088301] end_request: I/O error, dev mmcblk0, sector 1391352
<3>[ 9.088379] end_request: I/O error, dev mmcblk0, sector 1391360
<3>[ 9.088515] end_request: I/O error, dev mmcblk0, sector 1391368
<3>[ 9.088590] end_request: I/O error, dev mmcblk0, sector 1391376
<3>[ 9.088725] end_request: I/O error, dev mmcblk0, sector 1391384
<3>[ 9.088800] end_request: I/O error, dev mmcblk0, sector 1391392
<3>[ 9.088935] end_request: I/O error, dev mmcblk0, sector 1391400
<3>[ 9.089011] end_request: I/O error, dev mmcblk0, sector 1391408
<3>[ 9.089177] Aborting journal on device mmcblk0p4-8.
<0>[ 9.090018] journal commit I/O error
<4>[ 28.937444] adbd (125): /proc/125/oom_adj is deprecated, please use /proc/125/oom_score_adj instead.

i tried to mount /dev/block/mmcblk0p9 with the following error:

<3>[ 1252.621408] EXT3-fs (mmcblk0p9): error: couldn't mount because of unsupported optional features (40)
<3>[ 1252.670984] EXT2-fs (mmcblk0p9): error: couldn't mount because of unsupported optional features (44)
<3>[ 1255.510979] mmcblk0: error -110 transferring data, sector 5997888, nr 40, cmd response 0x900, card status 0x4000d00
<3>[ 1255.511068] end_request: I/O error, dev mmcblk0, sector 5997888
<4>[ 1255.511204] quiet_error: 2283 callbacks suppressed
<3>[ 1255.511279] Buffer I/O error on device mmcblk0p9, logical block 458792
<4>[ 1255.511412] lost page write due to I/O error on mmcblk0p9
<3>[ 1255.511489] end_request: I/O error, dev mmcblk0, sector 5997896
<3>[ 1255.511624] Buffer I/O error on device mmcblk0p9, logical block 458793
<4>[ 1255.511755] lost page write due to I/O error on mmcblk0p9
<3>[ 1255.511828] end_request: I/O error, dev mmcblk0, sector 5997904
<3>[ 1255.511962] Buffer I/O error on device mmcblk0p9, logical block 458794
<4>[ 1255.512036] lost page write due to I/O error on mmcblk0p9
<3>[ 1255.512172] end_request: I/O error, dev mmcblk0, sector 5997912
<3>[ 1255.512247] Buffer I/O error on device mmcblk0p9, logical block 458795
<4>[ 1255.512379] lost page write due to I/O error on mmcblk0p9
<3>[ 1255.512454] end_request: I/O error, dev mmcblk0, sector 5997920
<3>[ 1255.512588] Buffer I/O error on device mmcblk0p9, logical block 458796
<4>[ 1255.512661] lost page write due to I/O error on mmcblk0p9
<3>[ 1255.543050] mmcblk0: error -110 transferring data, sector 6526376, nr 40, cmd response 0x900, card status 0x4000d00
<3>[ 1255.543191] end_request: I/O error, dev mmcblk0, sector 6526376
<3>[ 1255.543268] Buffer I/O error on device mmcblk0p9, logical block 524853
<4>[ 1255.543400] lost page write due to I/O error on mmcblk0p9
<3>[ 1255.543476] end_request: I/O error, dev mmcblk0, sector 6526384
<3>[ 1255.543607] Buffer I/O error on device mmcblk0p9, logical block 524854
<4>[ 1255.543679] lost page write due to I/O error on mmcblk0p9
<3>[ 1255.543811] end_request: I/O error, dev mmcblk0, sector 6526392
<3>[ 1255.543885] Buffer I/O error on device mmcblk0p9, logical block 524855
<4>[ 1255.544015] lost page write due to I/O error on mmcblk0p9
<3>[ 1255.544089] end_request: I/O error, dev mmcblk0, sector 6526400
<3>[ 1255.544221] Buffer I/O error on device mmcblk0p9, logical block 524856
<4>[ 1255.544351] lost page write due to I/O error on mmcblk0p9
<3>[ 1255.544426] end_request: I/O error, dev mmcblk0, sector 6526408
<3>[ 1255.544571] Buffer I/O error on device mmcblk0p9, logical block 524857
<4>[ 1255.544644] lost page write due to I/O error on mmcblk0p9
<3>[ 1255.573641] mmcblk0: error -110 transferring data, sector 13861888, nr 40, cmd response 0x900, card status 0x4000d00
<3>[ 1255.573780] end_request: I/O error, dev mmcblk0, sector 13861888
<3>[ 1255.573870] end_request: I/O error, dev mmcblk0, sector 13861896
<3>[ 1255.574004] end_request: I/O error, dev mmcblk0, sector 13861904
<3>[ 1255.574080] end_request: I/O error, dev mmcblk0, sector 13861912
<3>[ 1255.574215] end_request: I/O error, dev mmcblk0, sector 13861920
<3>[ 1255.583454] mmcblk0: error -110 transferring data, sector 13862120, nr 40, cmd response 0x900, card status 0x4000d00
<3>[ 1255.583593] end_request: I/O error, dev mmcblk0, sector 13862120
<3>[ 1255.583732] end_request: I/O error, dev mmcblk0, sector 13862128
<3>[ 1255.583808] end_request: I/O error, dev mmcblk0, sector 13862136
<3>[ 1255.583944] end_request: I/O error, dev mmcblk0, sector 13862144
<3>[ 1255.584019] end_request: I/O error, dev mmcblk0, sector 13862152
<4>[ 1255.597238] JBD: recovery failed
<3>[ 1255.597322] EXT4-fs (mmcblk0p9): error loading journal

I tried to erase the Memory with "dd if=/dev/zero of=/dev/block/mmcblk0p9". Dmesg was flooding with:

<3>[ 150.817559] end_request: I/O error, dev mmcblk0, sector 2503504
<3>[ 150.817665] end_request: I/O error, dev mmcblk0, sector 2503512
<3>[ 150.817842] end_request: I/O error, dev mmcblk0, sector 2503520

Also fastboot flash recovery/system etc. wont work.

It looks like the eMMC Chip died and got Read-Only.

I backed up the data by mounting with "-o loop,ro,noexec,noload" and ADB Pull. The chip dont write any changes back.

Any suggestions to fix the eMMC Chip?

Thanks