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NFSv4.1: Fix the callback 'highest_used_slotid' behaviour

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Currently, there is no guarantee that we will call nfs4_cb_take_slot() even
though nfs4_callback_compound() will consistently call
nfs4_cb_free_slot() provided the cb_process_state has set the 'clp' field.
The result is that we can trigger the BUG_ON() upon the next call to
nfs4_cb_take_slot().

This patch fixes the above problem by using the slot id that was taken in
the CB_SEQUENCE operation as a flag for whether or not we need to call
nfs4_cb_free_slot().
It also fixes an atomicity problem: we need to set tbl->highest_used_slotid
atomically with the check for NFS4_SESSION_DRAINING, otherwise we end up
racing with the various tests in nfs4_begin_drain_session().

Cc: stable@kernel.org [2.6.38+]
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
This commit is contained in:
Trond Myklebust
2011-08-02 14:46:29 -04:00
parent 9af7db3228
commit 55a673990e
3 changed files with 22 additions and 24 deletions
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20
fs/nfs/callback_proc.c
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@@ -348,7 +348,7 @@ validate_seqid(struct nfs4_slot_table *tbl, struct cb_sequenceargs * args)
/* Normal */
if (likely(args->csa_sequenceid == slot->seq_nr + 1)) {
slot->seq_nr++;
return htonl(NFS4_OK);
goto out_ok;
}
/* Replay */
@@ -367,11 +367,14 @@ validate_seqid(struct nfs4_slot_table *tbl, struct cb_sequenceargs * args)
/* Wraparound */
if (args->csa_sequenceid == 1 && (slot->seq_nr + 1) == 0) {
slot->seq_nr = 1;
return htonl(NFS4_OK);
goto out_ok;
}
/* Misordered request */
return htonl(NFS4ERR_SEQ_MISORDERED);
out_ok:
tbl->highest_used_slotid = args->csa_slotid;
return htonl(NFS4_OK);
}
/*
@@ -433,26 +436,32 @@ __be32 nfs4_callback_sequence(struct cb_sequenceargs *args,
struct cb_sequenceres *res,
struct cb_process_state *cps)
{
struct nfs4_slot_table *tbl;
struct nfs_client *clp;
int i;
__be32 status = htonl(NFS4ERR_BADSESSION);
cps->clp = NULL;
clp = nfs4_find_client_sessionid(args->csa_addr, &args->csa_sessionid);
if (clp == NULL)
goto out;
tbl = &clp->cl_session->bc_slot_table;
spin_lock(&tbl->slot_tbl_lock);
/* state manager is resetting the session */
if (test_bit(NFS4_SESSION_DRAINING, &clp->cl_session->session_state)) {
status = NFS4ERR_DELAY;
spin_unlock(&tbl->slot_tbl_lock);
status = htonl(NFS4ERR_DELAY);
goto out;
}
status = validate_seqid(&clp->cl_session->bc_slot_table, args);
spin_unlock(&tbl->slot_tbl_lock);
if (status)
goto out;
cps->slotid = args->csa_slotid;
/*
* Check for pending referring calls. If a match is found, a
* related callback was received before the response to the original
@@ -469,7 +478,6 @@ __be32 nfs4_callback_sequence(struct cb_sequenceargs *args,
res->csr_slotid = args->csa_slotid;
res->csr_highestslotid = NFS41_BC_MAX_CALLBACKS - 1;
res->csr_target_highestslotid = NFS41_BC_MAX_CALLBACKS - 1;
nfs4_cb_take_slot(clp);
out:
cps->clp = clp; /* put in nfs4_callback_compound */