[Pvfs2-developers] concurrent ls and rm

[Rob Ross]

Are those cookies not somehow tied to a particular client?

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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