Messages in this thread | | | From | Chuck Lever <> | Subject | Re: [PATCH] SUNRPC: have soft RPC tasks return -ETIMEDOUT instead of -EIO on major connect timeout | Date | Mon, 31 Mar 2008 15:53:58 -0400 |
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On Mar 29, 2008, at 12:44 PM, Trond Myklebust wrote: > On Sat, 2008-03-29 at 08:49 -0400, Jeff Layton wrote: >> NFSv4 background mounts do not currently work correctly. While we >> could >> try to fix this in userspace, I think it's really a kernel problem... >> >> When a soft RPC tasks experiences a major timeout during a connection >> attempt, it does an rpc_exit with a return code of -EIO. For NFSv4 >> mounts, this makes the mount() syscall return -EIO. mount.nfs4 then >> interprets that as a "permanent" error, and won't attempt a >> background >> mount when bg is specified. Fix this by making call_timeout() do the >> rpc_exit() with an error of -ETIMEDOUT. >> >> This fixes the background mount issue, but does make other syscalls >> on soft mounts return ETIMEDOUT instead of EIO in this situation. >> >> Comments welcome. >> >> Signed-off-by: Jeff Layton <jlayton@redhat.com> >> --- >> net/sunrpc/clnt.c | 2 +- >> 1 files changed, 1 insertions(+), 1 deletions(-) >> >> diff --git a/net/sunrpc/clnt.c b/net/sunrpc/clnt.c >> index 8c6a7f1..b6d409e 100644 >> --- a/net/sunrpc/clnt.c >> +++ b/net/sunrpc/clnt.c >> @@ -1162,7 +1162,7 @@ call_timeout(struct rpc_task *task) >> if (RPC_IS_SOFT(task)) { >> printk(KERN_NOTICE "%s: server %s not responding, timed out\n", >> clnt->cl_protname, clnt->cl_server); >> - rpc_exit(task, -EIO); >> + rpc_exit(task, -ETIMEDOUT); >> return; >> } > > While that may be acceptable for the mount() syscall, I don't think > POSIX applications are quite ready to deal with ETIMEDOUT as an error > for stat() or chdir().
Having the RPC client throw -EIO on a timeout always seemed a little crude to me. EIO is quite overloaded -- the same error is returned if there's a XDR decoding error, for example. Clearly other consumers of RPC (mount, for example) would like a distinction between a timeout and an outright I/O error.
The fact that applications using NFS files can't deal with -ETIMEDOUT should probably be managed in the NFS client, not in the RPC client. Perhaps it could be handled with a wrapper function, like the NFS client handles EJUKEBOX.
So I agree that Jeff's patch is insufficient as it stands, but the underlying idea is probably a good one.
> Userland has the clnt_geterr() function that returns more detailed > 'RPC > level' errors. While that 'error function call' approach doesn't > work in > a multi-threaded environment, we might still be able to add the > equivalent of a pointer to an 'rpc_err' structure to the rpc_task, and > then have functions like call_timeout() (and especially call_verify > ()!) > fill in more detailed error info if that pointer is non-zero?
That's not a bad idea either.
-- Chuck Lever chuck[dot]lever[at]oracle[dot]com
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