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[Ltib] RE: JFFS2 crc errors

From: Chris Westervelt
Subject: [Ltib] RE: JFFS2 crc errors
Date: Fri, 6 Aug 2010 07:27:03 -0500

Thanks Kevin and Giri.  I have looked at the pages sent by Giri and I have a much better understanding of the whole thing now.


From: Kevin Wells [mailto:address@hidden
Sent: Thursday, August 05, 2010 4:48 PM
To: Bangaragiri G; Chris Westervelt
Cc: address@hidden
Subject: RE: JFFS2 crc errors


Hi Chris,


I think you’re ok and it’s just an artifact of stopping the garbage collector daemon….but this question might be better suited for the MTD/JFFS2 forums.

In the link Giri provided, I think you’re looking at unclean reboot case when the GC was working.


I did run a test on my board where I filled a JFFS2 partition with files, erased them all, and then refilled them again with other files. And then shut down the system (safely) with the garbage collector daemon still running and before it was complete without un-mounting the partition. On my next boot, the thread found the same type of error. If I un-mounted the partition and shut down, it was ok.


During garbage collection, you’ll see this running…

  436     2 root     RWN      0   0%  39% [jffs2_gcd_mtd4]


And here is the error on my board. On my board, the error showed up about 20 seconds after the partition was mounted and when gcd was running…

address@hidden /]# JFFS2 notice: (436) check_node_data: wrong data CRC in data node at 0x03200000: read 0xb0b6030f, calculated 0x95e2caad.


You can also test out the MTD subsystem using the kernel MTD tests if you want to check the MTD support. These install as modules and will help verify NAND and the MTD driver are working correctly.





Subject: [Ltib] RE: JFFS2 crc errors


Hi Chris,


   More info regarding JFFS2 messages






From: address@hidden [mailto:address@hidden On Behalf Of Chris Westervelt
Sent: 2010 Aug 05 2:12 AM
To: address@hidden
Subject: [Ltib] RE: JFFS2 crc errors


No I  just made some changes to the rootfs and saved them back.  After a power down and reboot, it started reporting this.  The product cannot be software shut down and must tolerate abrupt power loss.  If that is something we must consider in design then I need to get any appropriate changes made to the hardware/software to correct or tolerate this condition.  This is not the first time I have seen this in fact it almost always happens when we change the rootfs in any way.  I just wanted to better understand it and make sure it’s not a problem.



From: Kevin Wells [mailto:address@hidden
Sent: Wednesday, August 04, 2010 3:53 PM
To: Chris Westervelt; address@hidden
Subject: RE: JFFS2 crc errors


Hi Chris,


This can happen if something is writing to the NAND when the system is abruptly powered off or reset. Only part of the data will have been written to NAND.

Was the board shut down with the ‘reboot’ or ‘poweroff’ commands? This should give you a safe shutdown of JFFS2. An abrupt power cycle or reset can lead to issues with JFFS2 data (similar to any file system).






Subject: [Ltib] JFFS2 crc errors




I have started the phase of our project where we are weaning off NFS and using JFFS2.  Now my understanding is the flash should work just like a normal drive but I am seeing errors about failed CRCs that I don’t understand.  Is this normal or do we have a real problem here?  Also, if it is normal, is there a way to suppress these messages and or automatic checks.  The following is what I see.


address@hidden /]# JFFS2 notice: (309) check_node_data: wrong data CRC in data node at 0x01dd4000: read 0x971bfcf, calculated 0xe401df4b.

JFFS2 notice: (309) check_node_data: wrong data CRC in data node at 0x01dd59b0: read 0x7299d564, calculated 0x4a339945.


Chris Westervelt

Senior Product Development Engineer

Infrasafe, Inc.
12612 Challenger Pkwy
Suite 300
Orlando, FL
Office:   (407) 926-6983

Mobile: (407) 595-7023       
Fax:    (407) 857-1635

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