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Diffstat (limited to '')
| -rw-r--r-- | net/sunrpc/xprtmultipath.c | 541 |
1 files changed, 541 insertions, 0 deletions
diff --git a/net/sunrpc/xprtmultipath.c b/net/sunrpc/xprtmultipath.c new file mode 100644 index 000000000..78c075a68 --- /dev/null +++ b/net/sunrpc/xprtmultipath.c @@ -0,0 +1,541 @@ +// 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 rpc_xprt_switch *xps, + 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 = xps->xps_nactive = 0; + atomic_long_set(&xps->xps_queuelen, 0); + xps->xps_net = NULL; + 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 +bool xprt_is_active(const struct rpc_xprt *xprt) +{ + return kref_read(&xprt->kref) != 0; +} + +static +struct rpc_xprt *xprt_switch_find_first_entry(struct list_head *head) +{ + struct rpc_xprt *pos; + + list_for_each_entry_rcu(pos, head, xprt_switch) { + if (xprt_is_active(pos)) + return pos; + } + return NULL; +} + +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; + bool found = false; + + list_for_each_entry_rcu(pos, head, xprt_switch) { + if (cur == pos) + found = true; + if (found && xprt_is_active(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; + bool found = false; + + list_for_each_entry_rcu(pos, head, xprt_switch) { + if (cur == prev) + found = true; + if (found && xprt_is_active(pos)) + return pos; + prev = pos; + } + return NULL; +} + +static +struct rpc_xprt *xprt_switch_set_next_cursor(struct rpc_xprt_switch *xps, + struct rpc_xprt **cursor, + xprt_switch_find_xprt_t find_next) +{ + struct rpc_xprt *pos, *old; + + old = smp_load_acquire(cursor); + pos = find_next(xps, old); + smp_store_release(cursor, pos); + 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); + + if (xps == NULL) + return NULL; + return xprt_switch_set_next_cursor(xps, &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_switch_find_next_entry_roundrobin(struct rpc_xprt_switch *xps, + const struct rpc_xprt *cur) +{ + struct list_head *head = &xps->xps_xprt_list; + struct rpc_xprt *xprt; + unsigned int nactive; + + for (;;) { + unsigned long xprt_queuelen, xps_queuelen; + + xprt = __xprt_switch_find_next_entry_roundrobin(head, cur); + if (!xprt) + break; + xprt_queuelen = atomic_long_read(&xprt->queuelen); + xps_queuelen = atomic_long_read(&xps->xps_queuelen); + nactive = READ_ONCE(xps->xps_nactive); + /* Exit loop if xprt_queuelen <= average queue length */ + if (xprt_queuelen * nactive <= xps_queuelen) + break; + cur = xprt; + } + return xprt; +} + +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_switch_find_next_entry_all(struct rpc_xprt_switch *xps, + const struct rpc_xprt *cur) +{ + return xprt_switch_find_next_entry(&xps->xps_xprt_list, cur); +} + +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_all); +} + +/* + * 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 + * @newswitch: 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, +}; |