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nfsd: hold a lighter-weight client reference over CB_RECALL_ANY 

Currently the CB_RECALL_ANY job takes a cl_rpc_users reference to the
client. While a callback job is technically an RPC that counter is
really more for client-driven RPCs, and this has the effect of
preventing the client from being unhashed until the callback completes.

If nfsd decides to send a CB_RECALL_ANY just as the client reboots, we
can end up in a situation where the callback can't complete on the (now
dead) callback channel, but the new client can't connect because the old
client can't be unhashed. This usually manifests as a NFS4ERR_DELAY
return on the CREATE_SESSION operation.

The job is only holding a reference to the client so it can clear a flag
after the RPC completes. Fix this by having CB_RECALL_ANY instead hold a
reference to the cl_nfsdfs.cl_ref. Typically we only take that sort of
reference when dealing with the nfsdfs info files, but it should work
appropriately here to ensure that the nfs4_client doesn't disappear.

Fixes: 44df6f439a ("NFSD: add delegation reaper to react to low memory condition")
Reported-by: Vladimir Benes <vbenes@redhat.com>
Signed-off-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
This commit is contained in:
Jeff Layton 2024-04-05 13:56:18 -04:00 committed by Chuck Lever
parent 05258a0a69
commit 10396f4df8
1 changed files with 2 additions and 5 deletions
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7
fs/nfsd/nfs4state.c
View File

@ -3042,12 +3042,9 @@ static void
nfsd4_cb_recall_any_release(struct nfsd4_callback *cb)
{
struct nfs4_client *clp = cb->cb_clp;
struct nfsd_net *nn = net_generic(clp->net, nfsd_net_id);
spin_lock(&nn->client_lock);
clear_bit(NFSD4_CLIENT_CB_RECALL_ANY, &clp->cl_flags);
put_client_renew_locked(clp);
spin_unlock(&nn->client_lock);
drop_client(clp);
}
static int
@ -6616,7 +6613,7 @@ deleg_reaper(struct nfsd_net *nn)
list_add(&clp->cl_ra_cblist, &cblist);
/* release in nfsd4_cb_recall_any_release */
atomic_inc(&clp->cl_rpc_users);
kref_get(&clp->cl_nfsdfs.cl_ref);
set_bit(NFSD4_CLIENT_CB_RECALL_ANY, &clp->cl_flags);
clp->cl_ra_time = ktime_get_boottime_seconds();
}