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nfsd: avoid races with wake_up_var()

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wake_up_var() needs a barrier after the important change is made in the
var and before wake_up_var() is called, else it is possible that a wake
up won't be sent when it should.

In each case here the var is changed in an "atomic" manner, so
smb_mb__after_atomic() is sufficient.

In one case the important change (removing the lease) is performed
*after* the wake_up, which is backwards.  The code survives in part
because the wait_var_event is given a timeout.

This patch adds the required barriers and calls destroy_delegation()
*before* waking any threads waiting for the delegation to be destroyed.

Signed-off-by: NeilBrown <neilb@suse.de>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
This commit is contained in:
NeilBrown
2024-08-30 17:03:17 +10:00
committed by Chuck Lever
parent 985eeae9c8
commit 15392c8cd1
1 changed files with 4 additions and 1 deletions
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5
fs/nfsd/nfs4state.c
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@@ -4706,6 +4706,7 @@ void nfsd4_cstate_clear_replay(struct nfsd4_compound_state *cstate)
if (so != NULL) {
cstate->replay_owner = NULL;
atomic_set(&so->so_replay.rp_locked, RP_UNLOCKED);
smp_mb__after_atomic();
wake_up_var(&so->so_replay.rp_locked);
nfs4_put_stateowner(so);
}
@@ -5006,6 +5007,7 @@ move_to_close_lru(struct nfs4_ol_stateid *s, struct net *net)
* so tell them to stop waiting.
*/
atomic_set(&oo->oo_owner.so_replay.rp_locked, RP_UNHASHED);
smp_mb__after_atomic();
wake_up_var(&oo->oo_owner.so_replay.rp_locked);
wait_event(close_wq, refcount_read(&s->st_stid.sc_count) == 2);
@@ -7475,8 +7477,9 @@ nfsd4_delegreturn(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
goto put_stateid;
trace_nfsd_deleg_return(stateid);
wake_up_var(d_inode(cstate->current_fh.fh_dentry));
destroy_delegation(dp);
smp_mb__after_atomic();
wake_up_var(d_inode(cstate->current_fh.fh_dentry));
put_stateid:
nfs4_put_stid(&dp->dl_stid);
out: