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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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fs/nfs/callback.h
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@ -38,6 +38,7 @@ enum nfs4_callback_opnum {
struct cb_process_state {
__be32 drc_status;
struct nfs_client *clp;
int slotid;
};
struct cb_compound_hdr_arg {
@ -166,7 +167,6 @@ extern unsigned nfs4_callback_layoutrecall(
void *dummy, struct cb_process_state *cps);
extern void nfs4_check_drain_bc_complete(struct nfs4_session *ses);
extern void nfs4_cb_take_slot(struct nfs_client *clp);
struct cb_devicenotifyitem {
uint32_t cbd_notify_type;