[Pvfs2-developers] concurrent ls and rm

[Sam Lang]

On Sep 5, 2007, at 10:47 AM, Rob Ross wrote:

> Are those cookies not somehow tied to a particular client?

No they're not.
-sam

>
> Sam Lang wrote:
>> On Sep 5, 2007, at 10:31 AM, Phil Carns wrote:
>>> We have run into a problem with running "rm -rf" and "ls"  
>>> concurrently on the same directory from different client nodes.   
>>> In the particular case that we are looking at, the directory has  
>>> about 7000 files in it but no subdirectories.  If we do an ls on  
>>> the directory while an "rm -rf" is running from a different  
>>> client, then the rm fails to remove all of the files.  It seems  
>>> to get worse if you do more than one ls while the rm is working.   
>>> This is on RHEL4 with 2.6.9.something kernels.
>>>
>>> Has anyone else seen this?  Any idea what the problem is?
>> Hi Phil,
>> The trove layer caches the position -> name mapping for positions  
>> it returns back to the client on a readdir.  The problem is  
>> probably related to caching those entries, where the readdir for  
>> the rm is iterating over the directory, and so inserting position - 
>> > name entries into the cache, and then ls is coming along and  
>> replacing those entries with its own, where the position is the  
>> same but the name is further down in the directory (because rm has  
>> removed some of them).  That's just a guess though.  You could see  
>> if disabling that position cache helps fix the problem, disabling  
>> it will cause the berkeley db iterate to walk through all the  
>> entries up to the position though, so its going to be much  
>> slower.  The position cache is in dbpf-keyval-pcache.c.
>> Probably the right long term solution is to return the name as the  
>> position, instead of an int.
>> -sam
>>>
>>> thanks,
>>> -Phil
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>