#7177 NORM Never A: mostly harmless JFFS2 notice: check_node_data: wrong data CRC in data node

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#7177: mostly harmless JFFS2 notice: check_node_data:  wrong data CRC in data node
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 Reporter:  jpritikin    |       Owner:  jg            
     Type:  enhancement  |      Status:  new           
 Priority:  normal       |   Milestone:  Never Assigned
Component:  distro       |     Version:  Update.1      
 Keywords:               |    Verified:  0             
 Blocking:               |   Blockedby:                
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 [http://lists.laptop.org/pipermail/devel/2008-June/014970.html see mailing
 list for original report]

 According to Dave Woodhouse, who wrote JFFS2, these notices typically
 mean that at some point you've hard powered off, and as a result JFFS
 has some uncommitted data lying around on flash.  It's almost always
 harmless, a part of the journal which was never committed: "either it
 was a new write which hadn't yet been synced, or it was a GC write
 which just doesn't achieve anything now."  However, these messages
 *could* indicate an actual problem -- "we never came up with a good
 heuristic for when _not_ to complain".  Woodhouse suggests that in the
 future "perhaps we should write a 'yes, I know there's a CRC failure'
 node _after_ the offending node, when we reboot and find it" since
 directly rewriting the node is not an option due to the mechanics of
 NAND flash; that would help confine these messages to immediately
 after a hard reboot.  At present, you'll keep seeing a "bad CRC"
 message every time that particular JFFS node is accessed until it is
 eventually GC'ed.

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Ticket URL: <http://dev.laptop.org/ticket/7177>
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