[Crash-utility] transaction_t in jbd module vs. transaction_t in jbd2 module

[Dave Anderson]

----- Original Message -----
> Hello,
> 
> We recently encountered an issue where a transaction_t struct appeared
> to be corrupt but this ended up being a symbol conflict as the customer
> was using ext3 and ext4 and had both modules in use. Unloading the jbd
> module did not help and the only way to see the correct representation
> of the the transaction_t struct in question was to restart crash without
> any modules loaded and load only the jbd2 module.

That may be the best way to deal with it, however...

> Is this a known issue? Is there a strategy that needs to be followed for
> dealing with duplicate symbols?

Yes it is a known issue.  You may be able to use "set scope <text-addr>"
using a text address from the jbd2 module that would "see" the relevant
structure:

 crash> help set
  NAME
    set - set a process context or internal crash variable
  
  SYNOPSIS
    set [[-a] [pid | taskp] | [-c cpu] | -p] | [crash_variable [setting]] | -v
  
  ... [ cut ] ...
  
    This command may also be used to set internal crash variables.  If no value
    argument is entered, the current value of the crash variable is shown.  These
    are the crash variables, acceptable arguments, and purpose:
  
  ... [ cut ] ...
  
             scope  text-addr    sets the text scope for viewing the definition
                                 of data structures; the "text-addr" argument
                                 must be a kernel or module text address, which
                                 may be expressed symbolically or as a hexadecimal
                                 value.
  
It sets the internal gdb block scope based upon the text address, but I can't
guarantee that it will always work.

Dave