On Sep 25, 2009, at 11:01 AM, Trond Myklebust wrote:
On Fri, 2009-09-25 at 07:29 +0300, Benny Halevy wrote:
The client cannot reuse a slot while the server's
still working on the previous RPC using it.
The symptom Bruce saw without this patch was occasional
ESERVERFAULT during Connectathon special tests, 30 MB write/read
test.
Reported-by: J. Bruce Fields <bfields@xxxxxxxxxxxx>
Tested-by: J. Bruce Fields <bfields@xxxxxxxxxxxx>
Signed-off-by: Benny Halevy <bhalevy@xxxxxxxxxxx>
---
fs/nfs/nfs4proc.c | 6 ++++++
1 files changed, 6 insertions(+), 0 deletions(-)
diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index be6544a..70895d6 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -386,6 +386,12 @@ static void nfs41_sequence_done(struct
nfs_client *clp,
spin_unlock(&clp->cl_lock);
return;
}
+
+ /* Do not free slot if retried while operation was in progress */
+ if (res->sr_status == -NFS4ERR_DELAY) {
+ dprintk("%s: Operation in progress\n", __func__);
+ return;
+ }
out:
/* The session may be reset by one of the error handlers. */
dprintk("%s: Error %d free the slot \n", __func__, res->sr_status);
OK... Can somebody please tell me how this is supposed to work? As far
as I can see, most callers of nfs41_sequence_done() are calling
nfs41_sequence_free_slot() themselves.
IOW: Who is responsible for calling nfs41_sequence_free_slot()? Is it
nfs41_sequence_done(), or is it the callers, or is it some combination
of the two (and if so, what determines who calls it)?
It's a combination.
nfs41_sequence_free_slot was separated from nfs41_sequence_done so
that the error handling code such as nfs4_async_handle_error or
calling rpc_restart could retry a call using the same session slot -
we didn't want to give up the slot just to wait for a new slot.
So nfs41_sequence_free_slot is called by the callers of
nfs41_sequence_done when:
1) the caller either does not try to handle and error or restart.
nfs4_sequence_done_free_slot is used for this,
pnfs_layoutcommit_rpc_done is also an example.
2) The restart attempt is also done by the caller. nfs4_close_done is
an example where nfs4_async_handle_error is called in between the
calls to nfs4_sequence_done and nfs4_sequence free_slot.
nfs41_sequence_free_slot is not called by the caller of
nfs41_sequence_done when:
1) the caller does not contain the restart code. The read and write
paths are an example of this. For read, nfs4_sequence_done is called
in nfs4_read_done but the retry code is called in nfs_readpage_retry
which is where the corresponding nfs4_sequence_free_slot is called.
For write, nfs4_sequence_done is called in nfs4_write_done but the
retry code is in nfs_writeback_done where nfs4_sequence_free_slot is
called.
-->Andy
--
Trond Myklebust
Linux NFS client maintainer
NetApp
Trond.Myklebust@xxxxxxxxxx
www.netapp.com
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