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// SPDX-License-Identifier: GPL-2.0
/*
* Multipath support for RPC
*
* Copyright (c) 2015, 2016, Primary Data, Inc. All rights reserved.
*
* Trond Myklebust <trond.myklebust@primarydata.com>
*
*/
#include <linux/types.h>
#include <linux/kref.h>
#include <linux/list.h>
#include <linux/rcupdate.h>
#include <linux/rculist.h>
#include <linux/slab.h>
#include <asm/cmpxchg.h>
#include <linux/spinlock.h>
#include <linux/sunrpc/xprt.h>
#include <linux/sunrpc/addr.h>
#include <linux/sunrpc/xprtmultipath.h>
typedef struct rpc_xprt *(*xprt_switch_find_xprt_t)(struct list_head *head,
const struct rpc_xprt *cur);
static const struct rpc_xprt_iter_ops rpc_xprt_iter_singular;
static const struct rpc_xprt_iter_ops rpc_xprt_iter_roundrobin;
static const struct rpc_xprt_iter_ops rpc_xprt_iter_listall;
static void xprt_switch_add_xprt_locked(struct rpc_xprt_switch *xps,
struct rpc_xprt *xprt)
{
if (unlikely(xprt_get(xprt) == NULL))
return;
list_add_tail_rcu(&xprt->xprt_switch, &xps->xps_xprt_list);
smp_wmb();
if (xps->xps_nxprts == 0)
xps->xps_net = xprt->xprt_net;
xps->xps_nxprts++;
xps->xps_nactive++;
}
/**
* rpc_xprt_switch_add_xprt - Add a new rpc_xprt to an rpc_xprt_switch
* @xps: pointer to struct rpc_xprt_switch
* @xprt: pointer to struct rpc_xprt
*
* Adds xprt to the end of the list of struct rpc_xprt in xps.
*/
void rpc_xprt_switch_add_xprt(struct rpc_xprt_switch *xps,
struct rpc_xprt *xprt)
{
if (xprt == NULL)
return;
spin_lock(&xps->xps_lock);
if (xps->xps_net == xprt->xprt_net || xps->xps_net == NULL)
xprt_switch_add_xprt_locked(xps, xprt);
spin_unlock(&xps->xps_lock);
}
static void xprt_switch_remove_xprt_locked(struct rpc_xprt_switch *xps,
struct rpc_xprt *xprt)
{
if (unlikely(xprt == NULL))
return;
xps->xps_nactive--;
xps->xps_nxprts--;
if (xps->xps_nxprts == 0)
xps->xps_net = NULL;
smp_wmb();
list_del_rcu(&xprt->xprt_switch);
}
/**
* rpc_xprt_switch_remove_xprt - Removes an rpc_xprt from a rpc_xprt_switch
* @xps: pointer to struct rpc_xprt_switch
* @xprt: pointer to struct rpc_xprt
*
* Removes xprt from the list of struct rpc_xprt in xps.
*/
void rpc_xprt_switch_remove_xprt(struct rpc_xprt_switch *xps,
struct rpc_xprt *xprt)
{
spin_lock(&xps->xps_lock);
xprt_switch_remove_xprt_locked(xps, xprt);
spin_unlock(&xps->xps_lock);
xprt_put(xprt);
}
/**
* xprt_switch_alloc - Allocate a new struct rpc_xprt_switch
* @xprt: pointer to struct rpc_xprt
* @gfp_flags: allocation flags
*
* On success, returns an initialised struct rpc_xprt_switch, containing
* the entry xprt. Returns NULL on failure.
*/
struct rpc_xprt_switch *xprt_switch_alloc(struct rpc_xprt *xprt,
gfp_t gfp_flags)
{
struct rpc_xprt_switch *xps;
xps = kmalloc(sizeof(*xps), gfp_flags);
if (xps != NULL) {
spin_lock_init(&xps->xps_lock);
kref_init(&xps->xps_kref);
xps->xps_nxprts = 0;
INIT_LIST_HEAD(&xps->xps_xprt_list);
xps->xps_iter_ops = &rpc_xprt_iter_singular;
xprt_switch_add_xprt_locked(xps, xprt);
}
return xps;
}
static void xprt_switch_free_entries(struct rpc_xprt_switch *xps)
{
spin_lock(&xps->xps_lock);
while (!list_empty(&xps->xps_xprt_list)) {
struct rpc_xprt *xprt;
xprt = list_first_entry(&xps->xps_xprt_list,
struct rpc_xprt, xprt_switch);
xprt_switch_remove_xprt_locked(xps, xprt);
spin_unlock(&xps->xps_lock);
xprt_put(xprt);
spin_lock(&xps->xps_lock);
}
spin_unlock(&xps->xps_lock);
}
static void xprt_switch_free(struct kref *kref)
{
struct rpc_xprt_switch *xps = container_of(kref,
struct rpc_xprt_switch, xps_kref);
xprt_switch_free_entries(xps);
kfree_rcu(xps, xps_rcu);
}
/**
* xprt_switch_get - Return a reference to a rpc_xprt_switch
* @xps: pointer to struct rpc_xprt_switch
*
* Returns a reference to xps unless the refcount is already zero.
*/
struct rpc_xprt_switch *xprt_switch_get(struct rpc_xprt_switch *xps)
{
if (xps != NULL && kref_get_unless_zero(&xps->xps_kref))
return xps;
return NULL;
}
/**
* xprt_switch_put - Release a reference to a rpc_xprt_switch
* @xps: pointer to struct rpc_xprt_switch
*
* Release the reference to xps, and free it once the refcount is zero.
*/
void xprt_switch_put(struct rpc_xprt_switch *xps)
{
if (xps != NULL)
kref_put(&xps->xps_kref, xprt_switch_free);
}
/**
* rpc_xprt_switch_set_roundrobin - Set a round-robin policy on rpc_xprt_switch
* @xps: pointer to struct rpc_xprt_switch
*
* Sets a round-robin default policy for iterators acting on xps.
*/
void rpc_xprt_switch_set_roundrobin(struct rpc_xprt_switch *xps)
{
if (READ_ONCE(xps->xps_iter_ops) != &rpc_xprt_iter_roundrobin)
WRITE_ONCE(xps->xps_iter_ops, &rpc_xprt_iter_roundrobin);
}
static
const struct rpc_xprt_iter_ops *xprt_iter_ops(const struct rpc_xprt_iter *xpi)
{
if (xpi->xpi_ops != NULL)
return xpi->xpi_ops;
return rcu_dereference(xpi->xpi_xpswitch)->xps_iter_ops;
}
static
void xprt_iter_no_rewind(struct rpc_xprt_iter *xpi)
{
}
static
void xprt_iter_default_rewind(struct rpc_xprt_iter *xpi)
{
WRITE_ONCE(xpi->xpi_cursor, NULL);
}
static
struct rpc_xprt *xprt_switch_find_first_entry(struct list_head *head)
{
return list_first_or_null_rcu(head, struct rpc_xprt, xprt_switch);
}
static
struct rpc_xprt *xprt_iter_first_entry(struct rpc_xprt_iter *xpi)
{
struct rpc_xprt_switch *xps = rcu_dereference(xpi->xpi_xpswitch);
if (xps == NULL)
return NULL;
return xprt_switch_find_first_entry(&xps->xps_xprt_list);
}
static
struct rpc_xprt *xprt_switch_find_current_entry(struct list_head *head,
const struct rpc_xprt *cur)
{
struct rpc_xprt *pos;
list_for_each_entry_rcu(pos, head, xprt_switch) {
if (cur == pos)
return pos;
}
return NULL;
}
static
struct rpc_xprt *xprt_iter_current_entry(struct rpc_xprt_iter *xpi)
{
struct rpc_xprt_switch *xps = rcu_dereference(xpi->xpi_xpswitch);
struct list_head *head;
if (xps == NULL)
return NULL;
head = &xps->xps_xprt_list;
if (xpi->xpi_cursor == NULL || xps->xps_nxprts < 2)
return xprt_switch_find_first_entry(head);
return xprt_switch_find_current_entry(head, xpi->xpi_cursor);
}
bool rpc_xprt_switch_has_addr(struct rpc_xprt_switch *xps,
const struct sockaddr *sap)
{
struct list_head *head;
struct rpc_xprt *pos;
if (xps == NULL || sap == NULL)
return false;
head = &xps->xps_xprt_list;
list_for_each_entry_rcu(pos, head, xprt_switch) {
if (rpc_cmp_addr_port(sap, (struct sockaddr *)&pos->addr)) {
pr_info("RPC: addr %s already in xprt switch\n",
pos->address_strings[RPC_DISPLAY_ADDR]);
return true;
}
}
return false;
}
static
struct rpc_xprt *xprt_switch_find_next_entry(struct list_head *head,
const struct rpc_xprt *cur)
{
struct rpc_xprt *pos, *prev = NULL;
list_for_each_entry_rcu(pos, head, xprt_switch) {
if (cur == prev)
return pos;
prev = pos;
}
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