[Pvfs2-developers] concurrent ls and rm

[Phil Carns]

>> I just stumbled on to something while trying to clean up my  previous 
>> tests.  If I have the pcache disabled, then rm -rf of a  large 
>> directory never works right, even if all of the other clients  are 
>> idle.  It is possible that we have the opposite problem?  That  
>> actually the pcache works fine it but it is the pcache miss case  that 
>> is broken?
>>
>> I'll switch back and forth a couple more times to confirm, but I'm  
>> pretty sure this is consistent.
> 
> 
> Yeah possibly.  It would make sense that ls while rm -rf would cause  
> that too.  The pcache is FIFO, so the pos->name entries might be  
> getting FIFO-ed out of the cache by the entries that ls is adding.   
> When the pcache misses, it uses the step_to function based on the  value 
> of the position (walks through all the entries).  It could just  be a 
> bug in that code, but honestly the readdir with removes always  confuses 
> me when the index is meant to keep track of the position.   How did it 
> work in the previous impl when we had a db per directory?
> 
> -sam

I confirmed that it seems to be a problem with the "pcache miss" path. 
If I disable the pcache, then rm -rf of a directory with just 50 entries 
fails.  Everything works fine if the pcache is enabled.  Here is an example:

# mkdir /mnt/pvfs2/testdir6

# for i in `seq 1 50`; do cp /etc/hosts /mnt/pvfs2/testdir6/$i; done

# rm -rf /mnt/pvfs2/testdir6
rm: cannot remove directory `/mnt/pvfs2/testdir6': Directory not empty

# ls /mnt/pvfs2/testdir6
33  34  35  36  37  38  39  40  41  42  43  44  45  46  47  48  49  50

# ls /mnt/pvfs2/testdir6 |wc
      18      18      54

-Phil