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Release 4.11 net/sunrpc/xprtmultipath.c

Directory: net/sunrpc
/*
 * 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++; }

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/** * 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) && !rpc_xprt_switch_has_addr(xps, (struct sockaddr *)&xprt->addr)) xprt_switch_add_xprt_locked(xps, xprt); spin_unlock(&xps->xps_lock); }

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static void xprt_switch_remove_xprt_locked(struct rpc_xprt_switch *xps, struct rpc_xprt *xprt) { if (unlikely(xprt == NULL)) return; xps->xps_nxprts--; if (xps->xps_nxprts == 0) xps->xps_net = NULL; smp_wmb(); list_del_rcu(&xprt->xprt_switch); }

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/** * 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); }

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/** * 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; }

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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); }

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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); }

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/** * 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; }

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/** * 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); }

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/** * 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); }

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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; }

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static void xprt_iter_no_rewind(struct rpc_xprt_iter *xpi) { }

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static void xprt_iter_default_rewind(struct rpc_xprt_iter *xpi) { WRITE_ONCE(xpi->xpi_cursor, NULL); }

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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); }

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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); }

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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; }

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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); }

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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; }

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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; } return NULL; }

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static struct rpc_xprt *xprt_switch_set_next_cursor(struct list_head *head, struct rpc_xprt **cursor, xprt_switch_find_xprt_t find_next) { struct rpc_xprt *cur, *pos, *old; cur = READ_ONCE(*cursor); for (;;) { old = cur; pos = find_next(head, old); if (pos == NULL) break; cur = cmpxchg_relaxed(cursor, old, pos); if (cur == old) break; } return pos; }

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static struct rpc_xprt *xprt_iter_next_entry_multiple(struct rpc_xprt_iter *xpi, xprt_switch_find_xprt_t find_next) { struct rpc_xprt_switch *xps = rcu_dereference(xpi->xpi_xpswitch); if (xps == NULL) return NULL; return xprt_switch_set_next_cursor(&xps->xps_xprt_list, &xpi->xpi_cursor, find_next); }

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static struct rpc_xprt *xprt_switch_find_next_entry_roundrobin(struct list_head *head, const struct rpc_xprt *cur) { struct rpc_xprt *ret; ret = xprt_switch_find_next_entry(head, cur); if (ret != NULL) return ret; return xprt_switch_find_first_entry(head); }

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static struct rpc_xprt *xprt_iter_next_entry_roundrobin(struct rpc_xprt_iter *xpi) { return xprt_iter_next_entry_multiple(xpi, xprt_switch_find_next_entry_roundrobin); }

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static struct rpc_xprt *xprt_iter_next_entry_all(struct rpc_xprt_iter *xpi) { return xprt_iter_next_entry_multiple(xpi, xprt_switch_find_next_entry); }

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/* * xprt_iter_rewind - Resets the xprt iterator * @xpi: pointer to rpc_xprt_iter * * Resets xpi to ensure that it points to the first entry in the list * of transports. */
static void xprt_iter_rewind(struct rpc_xprt_iter *xpi) { rcu_read_lock(); xprt_iter_ops(xpi)->xpi_rewind(xpi); rcu_read_unlock(); }

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static void __xprt_iter_init(struct rpc_xprt_iter *xpi, struct rpc_xprt_switch *xps, const struct rpc_xprt_iter_ops *ops) { rcu_assign_pointer(xpi->xpi_xpswitch, xprt_switch_get(xps)); xpi->xpi_cursor = NULL; xpi->xpi_ops = ops; }

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/** * xprt_iter_init - Initialise an xprt iterator * @xpi: pointer to rpc_xprt_iter * @xps: pointer to rpc_xprt_switch * * Initialises the iterator to use the default iterator ops * as set in xps. This function is mainly intended for internal * use in the rpc_client. */
void xprt_iter_init(struct rpc_xprt_iter *xpi, struct rpc_xprt_switch *xps) { __xprt_iter_init(xpi, xps, NULL); }

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/** * xprt_iter_init_listall - Initialise an xprt iterator * @xpi: pointer to rpc_xprt_iter * @xps: pointer to rpc_xprt_switch * * Initialises the iterator to iterate once through the entire list * of entries in xps. */
void xprt_iter_init_listall(struct rpc_xprt_iter *xpi, struct rpc_xprt_switch *xps) { __xprt_iter_init(xpi, xps, &rpc_xprt_iter_listall); }

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/** * xprt_iter_xchg_switch - Atomically swap out the rpc_xprt_switch * @xpi: pointer to rpc_xprt_iter * @xps: pointer to a new rpc_xprt_switch or NULL * * Swaps out the existing xpi->xpi_xpswitch with a new value. */
struct rpc_xprt_switch *xprt_iter_xchg_switch(struct rpc_xprt_iter *xpi, struct rpc_xprt_switch *newswitch) { struct rpc_xprt_switch __rcu *oldswitch; /* Atomically swap out the old xpswitch */ oldswitch = xchg(&xpi->xpi_xpswitch, RCU_INITIALIZER(newswitch)); if (newswitch != NULL) xprt_iter_rewind(xpi); return rcu_dereference_protected(oldswitch, true); }

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/** * xprt_iter_destroy - Destroys the xprt iterator * @xpi pointer to rpc_xprt_iter */
void xprt_iter_destroy(struct rpc_xprt_iter *xpi) { xprt_switch_put(xprt_iter_xchg_switch(xpi, NULL)); }

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/** * xprt_iter_xprt - Returns the rpc_xprt pointed to by the cursor * @xpi: pointer to rpc_xprt_iter * * Returns a pointer to the struct rpc_xprt that is currently * pointed to by the cursor. * Caller must be holding rcu_read_lock(). */
struct rpc_xprt *xprt_iter_xprt(struct rpc_xprt_iter *xpi) { WARN_ON_ONCE(!rcu_read_lock_held()); return xprt_iter_ops(xpi)->xpi_xprt(xpi); }

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static struct rpc_xprt *xprt_iter_get_helper(struct rpc_xprt_iter *xpi, struct rpc_xprt *(*fn)(struct rpc_xprt_iter *)) { struct rpc_xprt *ret; do { ret = fn(xpi); if (ret == NULL) break; ret = xprt_get(ret); } while (ret == NULL); return ret; } /** * xprt_iter_get_xprt - Returns the rpc_xprt pointed to by the cursor * @xpi: pointer to rpc_xprt_iter * * Returns a reference to the struct rpc_xprt that is currently * pointed to by the cursor. */
struct rpc_xprt *xprt_iter_get_xprt(struct rpc_xprt_iter *xpi) { struct rpc_xprt *xprt; rcu_read_lock(); xprt = xprt_iter_get_helper(xpi, xprt_iter_ops(xpi)->xpi_xprt); rcu_read_unlock(); return xprt; }

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/** * xprt_iter_get_next - Returns the next rpc_xprt following the cursor * @xpi: pointer to rpc_xprt_iter * * Returns a reference to the struct rpc_xprt that immediately follows the * entry pointed to by the cursor. */
struct rpc_xprt *xprt_iter_get_next(struct rpc_xprt_iter *xpi) { struct rpc_xprt *xprt; rcu_read_lock(); xprt = xprt_iter_get_helper(xpi, xprt_iter_ops(xpi)->xpi_next); rcu_read_unlock(); return xprt; }

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/* Policy for always returning the first entry in the rpc_xprt_switch */ static const struct rpc_xprt_iter_ops rpc_xprt_iter_singular = { .xpi_rewind = xprt_iter_no_rewind, .xpi_xprt = xprt_iter_first_entry, .xpi_next = xprt_iter_first_entry, }; /* Policy for round-robin iteration of entries in the rpc_xprt_switch */ static const struct rpc_xprt_iter_ops rpc_xprt_iter_roundrobin = { .xpi_rewind = xprt_iter_default_rewind, .xpi_xprt = xprt_iter_current_entry, .xpi_next = xprt_iter_next_entry_roundrobin, }; /* Policy for once-through iteration of entries in the rpc_xprt_switch */ static const struct rpc_xprt_iter_ops rpc_xprt_iter_listall = { .xpi_rewind = xprt_iter_default_rewind, .xpi_xprt = xprt_iter_current_entry, .xpi_next = xprt_iter_next_entry_all, };

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