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// SPDX-License-Identifier: GPL-2.0-only
/*
* Helper for knfsd's SSC to access ops in NFS client modules
*
* Author: Dai Ngo <dai.ngo@oracle.com>
*
* Copyright (c) 2020, Oracle and/or its affiliates.
*/
#include <linux/module.h>
#include <linux/fs.h>
#include <linux/nfs_ssc.h>
#include <linux/nfsd_ssc.h>
struct nfs_ssc_client_ops_tbl {
const struct nfs4_ssc_client_ops __rcu *ssc_nfs4_ops;
};
static struct nfs_ssc_client_ops_tbl nfs_ssc_client_tbl __read_mostly;
/**
* nfsd42_ssc_open - Open a file to be used for server-to-server copy
* @ss_mnt: active mount point on which the source file resides
* @src_fh: file handle of the source file to be copied
* @stateid: stateid to use for COPY operation
*
* Caller must close the returned file using nfsd42_ssc_close().
*
* Return: an open file, or an ERR_PTR on error
*/
struct file *nfsd42_ssc_open(struct vfsmount *ss_mnt, struct nfs_fh *src_fh,
nfs4_stateid *stateid)
{
/*
* Built under CONFIG_NFS_V4_2_SSC_HELPER, which the NFS client
* enables on its own. The dispatch below is live only when the
* server also sets CONFIG_NFSD_V4_2_INTER_SSC; without it the
* source file cannot be opened, so callers get -EIO.
*/
#if IS_ENABLED(CONFIG_NFSD_V4_2_INTER_SSC)
const struct nfs4_ssc_client_ops *ops;
struct file *res;
/*
* sco_open() sleeps and must not run inside an RCU read-side
* section. Pin the provider module so the open runs with the
* module held; try_module_get() fails once unregister begins,
* and the copy then gets -EIO.
*/
rcu_read_lock();
ops = rcu_dereference(nfs_ssc_client_tbl.ssc_nfs4_ops);
if (ops && try_module_get(ops->owner)) {
rcu_read_unlock();
res = ops->sco_open(ss_mnt, src_fh, stateid);
module_put(ops->owner);
return res;
}
rcu_read_unlock();
#endif
return ERR_PTR(-EIO);
}
EXPORT_SYMBOL_GPL(nfsd42_ssc_open);
/**
* nfsd42_ssc_close - Close a file opened with nfsd42_ssc_open()
* @filp: struct file to be closed
*
* The real cleanup happens unconditionally in nfsd4_cleanup_inter_ssc().
* The client ops table is read under RCU; nfs42_ssc_unregister() calls
* synchronize_rcu() so unregistration cannot complete while a close is
* in flight.
*/
void nfsd42_ssc_close(struct file *filp)
{
/* Live only under CONFIG_NFSD_V4_2_INTER_SSC; see nfsd42_ssc_open(). */
#if IS_ENABLED(CONFIG_NFSD_V4_2_INTER_SSC)
const struct nfs4_ssc_client_ops *ops;
rcu_read_lock();
ops = rcu_dereference(nfs_ssc_client_tbl.ssc_nfs4_ops);
if (ops)
ops->sco_close(filp);
rcu_read_unlock();
#endif
}
EXPORT_SYMBOL_GPL(nfsd42_ssc_close);
#ifdef CONFIG_NFS_V4_2
/**
* nfs42_ssc_register - install the NFS_V4 client ops in the nfs_ssc_client_tbl
* @ops: NFS_V4 ops to be installed
*
* Return values:
* None
*/
void nfs42_ssc_register(const struct nfs4_ssc_client_ops *ops)
{
rcu_assign_pointer(nfs_ssc_client_tbl.ssc_nfs4_ops, ops);
}
EXPORT_SYMBOL_GPL(nfs42_ssc_register);
/**
* nfs42_ssc_unregister - uninstall the NFS_V4 client ops from
* the nfs_ssc_client_tbl
* @ops: ops to be uninstalled
*
* Return values:
* None
*/
void nfs42_ssc_unregister(const struct nfs4_ssc_client_ops *ops)
{
if (rcu_dereference_protected(nfs_ssc_client_tbl.ssc_nfs4_ops,
true) != ops)
return;
rcu_assign_pointer(nfs_ssc_client_tbl.ssc_nfs4_ops, NULL);
synchronize_rcu();
}
EXPORT_SYMBOL_GPL(nfs42_ssc_unregister);
#endif /* CONFIG_NFS_V4_2 */
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