open() and ESTALE error

[Andrey Alekseyev]

Terry,

Thanks much for you comments, but see below.

> The real problem here is that you know you did an operation
> on the file which would break the name/nfsnode relationship,
> but did not flush the cached name and nfsnode data.

nfs_request() actually calls cache_purge() on ESTALE, and vn_open()
frees vnode with vput() if a lookup was successful but there were
an error from the underlying filesystem (like ESTALE resulting from
nfs_request() which is eventually called from VOP_ACCESS or VOP_OPEN).

> A more correct solution would resync the nfsnode.

I think this is exactly what happens :) Actually, I believe, I'm just
getting another namecache entry with another vnode/nfsnode/file handle.

> The main problem with your solution is that it doesn't work
> in the case that you don't know the name of the remote file
> (in which case, all you really have is a stale file handle,
> with no way to unstale it).

I think, in this case (if the file was rm'd on the server), I'll just
get ENOENT from the second vn_open() attempt, which would be more
than appropriate. A real drawback is that for a stale "current"
directory it'll take another lookup to detect "true" ESTALE.

> This would fix a lot more cases than the single failure you
> are fixing.

Actually, as I said, I played with different parts of the code to solve
this (including, nfs_open(), nfs_access(), nfs_lookup() and vn_open())
only to find the previously mentioned solution to be the simpliest and
most suitable for all situations (for me!)  :)