On Sun, Nov 06, 2016 at 12:24:20PM +0000, Luis de Bethencourt wrote: > On 05/11/16 22:03, NeilBrown wrote: > > On Sat, Nov 05 2016, Luis de Bethencourt wrote: > > > >> Hi all, > >> > >> I recently played with adding the basics to make befs exportable via NFS [0]. > >> > >> I want to implement the get_parent member of the export_operations struct as > >> well, but I can't seem to trigger this member being called. I have implemented > >> a solution which I feel is wrong [1], but want to be able to test it before > >> moving forward. > >> > >> When is this member triggered? Any advice? > > > > This is required when a filehandle for a directory arrives, but the > > directory is not in the dcache. > > NFSD needs to find dentries for the directory, the parent, the > > grandparent etc all the way up to the root. > > > > The simplest way to trigger this is to mount the filesystem onto a > > different machine, 'cd' into a fairly deep directory, then reboot the > > server (or unexport, unmount, remount, re-export). > > Now 'ls -l' on the client. That should trigger calls to ->get_parent. > > > > ->get_parent() is a log like performing a lookup of "..". > > > > NeilBrown > > > > Nice! > > This makes a lot of sense. I just rebooted the server and saw the get_parent > being called. Before I was mistakenly trying without a reboot, but thanks to your > explanation now understand this better, the directory was still in the dcache and > it was using this instead. I've also tested get_parent with "echo 2>/proc/sys/vm/drop_caches", after first creating a 2000-deep subdirectory heirarchy (to stress performance, and to make sure dcache had enough entries that drop_caches would reliably drop what I wanted). And I used the filehandle syscalls directly, to take nfsd out of the equation. See deep-fh-lookup in git://linux-nfs.org/~bfields/fragments.git for my kludgey script. OK, rebooting may be easier. --b. -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
