[Pvfs2-developers] ncache causes shared creat problems

[Phil Carns]

Pete Wyckoff wrote:
> The simul code, test #14, does a shared create:  all processes
> try to do "creat(file, 0644)" at the same time through the VFS.
> There is no O_EXCL, so what should happen here is that they all
> succeed, although under the hood, all but one will probably have
> to unwind the SYS_CREATE when they notice that the dirent already
> exists from another process.
> 
> This used to work just fine.  With the addition of the ncache code
> to pvfs2-client, I'm guessing, things break.  The test works again
> if I add "-n 0" to the pvfs2-client command line.
> 
> My setup is all x86_64.  Two IO servers, one of which does MD too.
> Two other nodes as clients, running:
> 
>     mpiexec -pernode -np 2 $simul/simul -d /pvfs-ib -i 14 -n 200 -N 1
> 
> eventually one will fail, usually around the second iteration, with
> 
>     14:46:54: Process 1(ib26): FAILED in simul_creat, creat failed:
>     No such file or directory
> 
> Does anybody know the ncache code well enough to figure this out?
> I find the -EEXIST fixup code in client-core, but can't see what
> kind of ncache invalidation should presumably happen around there.
> 
> 		-- Pete

What happens on each iteration?  Does the code at some point delete a 
file with a particular name and then create a new one with the same name?

-Phil