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nfs_localio: simplify interface to nfsd for getting nfsd_file
The nfsd_localio_operations structure contains nfsd_file_get() to get a
reference to an nfsd_file. This is only used in one place, where
nfsd_open_local_fh() is also used.
This patch combines the two, calling nfsd_open_local_fh() passing a
pointer to where the nfsd_file pointer might be stored. If there is a
pointer there an nfsd_file_get() can get a reference, that reference is
returned. If not a new nfsd_file is acquired, stored at the pointer,
and returned. When we store a reference we also increase the refcount
on the net, as that refcount is decrements when we clear the stored
pointer.
We now get an extra reference *before* storing the new nfsd_file at the
given location. This avoids possible races with the nfsd_file being
freed before the final reference can be taken.
This patch moves the rcu_dereference() needed after fetching from
ro_file or rw_file into the nfsd code where the 'struct nfs_file' is
fully defined. This avoids an error reported by older versions of gcc
such as gcc-8 which complain about rcu_dereference() use in contexts
where the structure (which will supposedly be accessed) is not fully
defined.
Reported-by: Pali Rohár <pali@kernel.org>
Reported-by: Vincent Mailhol <mailhol.vincent@wanadoo.fr>
Fixes: 86e0041225 ("nfs: cache all open LOCALIO nfsd_file(s) in client")
Signed-off-by: NeilBrown <neil@brown.name>
Signed-off-by: Anna Schumaker <anna.schumaker@oracle.com>
This commit is contained in:
NeilBrown
Anna Schumaker
parent
77e82fb2c6
commit
e6f7e1487a
3 changed files with 55 additions and 44 deletions
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@ -209,11 +209,6 @@ void nfs_local_probe_async(struct nfs_client *clp)
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}
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EXPORT_SYMBOL_GPL(nfs_local_probe_async);
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static inline struct nfsd_file *nfs_local_file_get(struct nfsd_file *nf)
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{
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return nfs_to->nfsd_file_get_local(nf);
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}
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static inline void nfs_local_file_put(struct nfsd_file *nf)
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{
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nfs_to_nfsd_file_put_local(nf);
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@ -228,12 +223,13 @@ static inline void nfs_local_file_put(struct nfsd_file *nf)
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static struct nfsd_file *
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__nfs_local_open_fh(struct nfs_client *clp, const struct cred *cred,
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struct nfs_fh *fh, struct nfs_file_localio *nfl,
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struct nfsd_file __rcu **pnf,
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const fmode_t mode)
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{
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struct nfsd_file *localio;
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localio = nfs_open_local_fh(&clp->cl_uuid, clp->cl_rpcclient,
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cred, fh, nfl, mode);
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cred, fh, nfl, pnf, mode);
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if (IS_ERR(localio)) {
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int status = PTR_ERR(localio);
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trace_nfs_local_open_fh(fh, mode, status);
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@ -260,7 +256,7 @@ nfs_local_open_fh(struct nfs_client *clp, const struct cred *cred,
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struct nfs_fh *fh, struct nfs_file_localio *nfl,
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const fmode_t mode)
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{
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struct nfsd_file *nf, *new, __rcu **pnf;
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struct nfsd_file *nf, __rcu **pnf;
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if (!nfs_server_is_local(clp))
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return NULL;
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@ -272,24 +268,9 @@ nfs_local_open_fh(struct nfs_client *clp, const struct cred *cred,
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else
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pnf = &nfl->ro_file;
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new = NULL;
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rcu_read_lock();
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nf = rcu_dereference(*pnf);
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if (!nf) {
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rcu_read_unlock();
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new = __nfs_local_open_fh(clp, cred, fh, nfl, mode);
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if (IS_ERR(new))
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nf = __nfs_local_open_fh(clp, cred, fh, nfl, pnf, mode);
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if (IS_ERR(nf))
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return NULL;
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rcu_read_lock();
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/* try to swap in the pointer */
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nf = unrcu_pointer(cmpxchg(pnf, NULL, RCU_INITIALIZER(new)));
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if (!nf)
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swap(nf, new);
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}
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nf = nfs_local_file_get(nf);
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rcu_read_unlock();
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if (new)
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nfs_to_nfsd_file_put_local(new);
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return nf;
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}
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EXPORT_SYMBOL_GPL(nfs_local_open_fh);
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@ -237,6 +237,7 @@ static void nfs_uuid_add_file(nfs_uuid_t *nfs_uuid, struct nfs_file_localio *nfl
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struct nfsd_file *nfs_open_local_fh(nfs_uuid_t *uuid,
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struct rpc_clnt *rpc_clnt, const struct cred *cred,
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const struct nfs_fh *nfs_fh, struct nfs_file_localio *nfl,
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struct nfsd_file __rcu **pnf,
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const fmode_t fmode)
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{
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struct net *net;
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@ -261,7 +262,7 @@ struct nfsd_file *nfs_open_local_fh(nfs_uuid_t *uuid,
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rcu_read_unlock();
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/* We have an implied reference to net thanks to nfsd_net_try_get */
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localio = nfs_to->nfsd_open_local_fh(net, uuid->dom, rpc_clnt,
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cred, nfs_fh, fmode);
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cred, nfs_fh, pnf, fmode);
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nfs_to_nfsd_net_put(net);
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if (!IS_ERR(localio))
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nfs_uuid_add_file(uuid, nfl);
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@ -24,20 +24,6 @@
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#include "filecache.h"
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#include "cache.h"
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static const struct nfsd_localio_operations nfsd_localio_ops = {
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.nfsd_net_try_get = nfsd_net_try_get,
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.nfsd_net_put = nfsd_net_put,
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.nfsd_open_local_fh = nfsd_open_local_fh,
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.nfsd_file_put_local = nfsd_file_put_local,
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.nfsd_file_get_local = nfsd_file_get_local,
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.nfsd_file_file = nfsd_file_file,
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};
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void nfsd_localio_ops_init(void)
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{
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nfs_to = &nfsd_localio_ops;
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}
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/**
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* nfsd_open_local_fh - lookup a local filehandle @nfs_fh and map to nfsd_file
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*
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@ -46,6 +32,7 @@ void nfsd_localio_ops_init(void)
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* @rpc_clnt: rpc_clnt that the client established
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* @cred: cred that the client established
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* @nfs_fh: filehandle to lookup
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* @nfp: place to find the nfsd_file, or store it if it was non-NULL
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* @fmode: fmode_t to use for open
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*
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* This function maps a local fh to a path on a local filesystem.
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@ -56,10 +43,11 @@ void nfsd_localio_ops_init(void)
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* set. Caller (NFS client) is responsible for calling nfsd_net_put and
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* nfsd_file_put (via nfs_to_nfsd_file_put_local).
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*/
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struct nfsd_file *
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static struct nfsd_file *
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nfsd_open_local_fh(struct net *net, struct auth_domain *dom,
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struct rpc_clnt *rpc_clnt, const struct cred *cred,
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const struct nfs_fh *nfs_fh, const fmode_t fmode)
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const struct nfs_fh *nfs_fh, struct nfsd_file __rcu **pnf,
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const fmode_t fmode)
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{
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int mayflags = NFSD_MAY_LOCALIO;
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struct svc_cred rq_cred;
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@ -73,6 +61,12 @@ nfsd_open_local_fh(struct net *net, struct auth_domain *dom,
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if (!nfsd_net_try_get(net))
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return ERR_PTR(-ENXIO);
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rcu_read_lock();
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localio = nfsd_file_get(rcu_dereference(*pnf));
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rcu_read_unlock();
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if (localio)
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return localio;
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/* nfs_fh -> svc_fh */
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fh_init(&fh, NFS4_FHSIZE);
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fh.fh_handle.fh_size = nfs_fh->size;
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@ -94,12 +88,47 @@ nfsd_open_local_fh(struct net *net, struct auth_domain *dom,
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if (rq_cred.cr_group_info)
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put_group_info(rq_cred.cr_group_info);
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if (IS_ERR(localio))
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if (!IS_ERR(localio)) {
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struct nfsd_file *new;
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if (!nfsd_net_try_get(net)) {
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nfsd_file_put(localio);
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nfsd_net_put(net);
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return ERR_PTR(-ENXIO);
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}
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nfsd_file_get(localio);
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again:
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new = unrcu_pointer(cmpxchg(pnf, NULL, RCU_INITIALIZER(localio)));
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if (new) {
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/* Some other thread installed an nfsd_file */
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if (nfsd_file_get(new) == NULL)
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goto again;
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/*
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* Drop the ref we were going to install and the
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* one we were going to return.
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*/
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nfsd_file_put(localio);
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nfsd_file_put(localio);
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localio = new;
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}
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} else
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nfsd_net_put(net);
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return localio;
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}
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EXPORT_SYMBOL_GPL(nfsd_open_local_fh);
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static const struct nfsd_localio_operations nfsd_localio_ops = {
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.nfsd_net_try_get = nfsd_net_try_get,
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.nfsd_net_put = nfsd_net_put,
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.nfsd_open_local_fh = nfsd_open_local_fh,
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.nfsd_file_put_local = nfsd_file_put_local,
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.nfsd_file_get_local = nfsd_file_get_local,
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.nfsd_file_file = nfsd_file_file,
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};
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void nfsd_localio_ops_init(void)
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{
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nfs_to = &nfsd_localio_ops;
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}
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/*
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* UUID_IS_LOCAL XDR functions
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