--- /dev/null
+/*
+ * 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/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++;
+}
+
+/**
+ * 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_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);
+}
+
+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;
+}
+
+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;
+}
+
+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);
+ struct list_head *head;
+
+ if (xps == NULL)
+ return NULL;
+ head = &xps->xps_xprt_list;
+ if (xps->xps_nxprts < 2)
+ return xprt_switch_find_first_entry(head);
+ return xprt_switch_set_next_cursor(head, &xpi->xpi_cursor, find_next);
+}
+
+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);
+}
+
+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);
+}
+
+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);
+}
+
+/*
+ * 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();
+}
+
+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;
+}
+
+/**
+ * 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);
+}
+
+/**
+ * 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);
+}
+
+/**
+ * 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);
+}
+
+/**
+ * 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));
+}
+
+/**
+ * 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);
+}
+
+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;
+}
+
+/**
+ * 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;
+}
+
+/* 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,
+};
projects / cascardo / linux.git / commitdiff