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authorMike Snitzer <snitzer@redhat.com>2020-11-10 13:41:53 -0500
committerMike Snitzer <snitzer@redhat.com>2020-12-04 18:04:35 -0500
commit298fb372984a808ccba9ca15a9cf0f393b3259b4 (patch)
tree4f2fbce4b608dbb6c8cd523ca177beb6d419bdbc /drivers/md/dm-ps-queue-length.c
parente4d2e82b2300b03f66b3ca8417590c86e661fab1 (diff)
downloadlinux-298fb372984a808ccba9ca15a9cf0f393b3259b4.tar.bz2
dm: rename multipath path selector source files to have "dm-ps" prefix
Additional prefix helps clarify that these source files implement path selectors. Required updating Makefile to still build modules _without_ the "dm-ps" prefix to preserve dm-multipath's ability to autoload path selector modules. While at it, cleaned up some DM whitespace in Makefile. Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Diffstat (limited to 'drivers/md/dm-ps-queue-length.c')
-rw-r--r--drivers/md/dm-ps-queue-length.c283
1 files changed, 283 insertions, 0 deletions
diff --git a/drivers/md/dm-ps-queue-length.c b/drivers/md/dm-ps-queue-length.c
new file mode 100644
index 000000000000..5fd018d18418
--- /dev/null
+++ b/drivers/md/dm-ps-queue-length.c
@@ -0,0 +1,283 @@
+/*
+ * Copyright (C) 2004-2005 IBM Corp. All Rights Reserved.
+ * Copyright (C) 2006-2009 NEC Corporation.
+ *
+ * dm-queue-length.c
+ *
+ * Module Author: Stefan Bader, IBM
+ * Modified by: Kiyoshi Ueda, NEC
+ *
+ * This file is released under the GPL.
+ *
+ * queue-length path selector - choose a path with the least number of
+ * in-flight I/Os.
+ */
+
+#include "dm.h"
+#include "dm-path-selector.h"
+
+#include <linux/slab.h>
+#include <linux/ctype.h>
+#include <linux/errno.h>
+#include <linux/module.h>
+#include <linux/atomic.h>
+
+#define DM_MSG_PREFIX "multipath queue-length"
+#define QL_MIN_IO 1
+#define QL_VERSION "0.2.0"
+
+struct selector {
+ struct list_head valid_paths;
+ struct list_head failed_paths;
+ spinlock_t lock;
+};
+
+struct path_info {
+ struct list_head list;
+ struct dm_path *path;
+ unsigned repeat_count;
+ atomic_t qlen; /* the number of in-flight I/Os */
+};
+
+static struct selector *alloc_selector(void)
+{
+ struct selector *s = kmalloc(sizeof(*s), GFP_KERNEL);
+
+ if (s) {
+ INIT_LIST_HEAD(&s->valid_paths);
+ INIT_LIST_HEAD(&s->failed_paths);
+ spin_lock_init(&s->lock);
+ }
+
+ return s;
+}
+
+static int ql_create(struct path_selector *ps, unsigned argc, char **argv)
+{
+ struct selector *s = alloc_selector();
+
+ if (!s)
+ return -ENOMEM;
+
+ ps->context = s;
+ return 0;
+}
+
+static void ql_free_paths(struct list_head *paths)
+{
+ struct path_info *pi, *next;
+
+ list_for_each_entry_safe(pi, next, paths, list) {
+ list_del(&pi->list);
+ kfree(pi);
+ }
+}
+
+static void ql_destroy(struct path_selector *ps)
+{
+ struct selector *s = ps->context;
+
+ ql_free_paths(&s->valid_paths);
+ ql_free_paths(&s->failed_paths);
+ kfree(s);
+ ps->context = NULL;
+}
+
+static int ql_status(struct path_selector *ps, struct dm_path *path,
+ status_type_t type, char *result, unsigned maxlen)
+{
+ unsigned sz = 0;
+ struct path_info *pi;
+
+ /* When called with NULL path, return selector status/args. */
+ if (!path)
+ DMEMIT("0 ");
+ else {
+ pi = path->pscontext;
+
+ switch (type) {
+ case STATUSTYPE_INFO:
+ DMEMIT("%d ", atomic_read(&pi->qlen));
+ break;
+ case STATUSTYPE_TABLE:
+ DMEMIT("%u ", pi->repeat_count);
+ break;
+ }
+ }
+
+ return sz;
+}
+
+static int ql_add_path(struct path_selector *ps, struct dm_path *path,
+ int argc, char **argv, char **error)
+{
+ struct selector *s = ps->context;
+ struct path_info *pi;
+ unsigned repeat_count = QL_MIN_IO;
+ char dummy;
+ unsigned long flags;
+
+ /*
+ * Arguments: [<repeat_count>]
+ * <repeat_count>: The number of I/Os before switching path.
+ * If not given, default (QL_MIN_IO) is used.
+ */
+ if (argc > 1) {
+ *error = "queue-length ps: incorrect number of arguments";
+ return -EINVAL;
+ }
+
+ if ((argc == 1) && (sscanf(argv[0], "%u%c", &repeat_count, &dummy) != 1)) {
+ *error = "queue-length ps: invalid repeat count";
+ return -EINVAL;
+ }
+
+ if (repeat_count > 1) {
+ DMWARN_LIMIT("repeat_count > 1 is deprecated, using 1 instead");
+ repeat_count = 1;
+ }
+
+ /* Allocate the path information structure */
+ pi = kmalloc(sizeof(*pi), GFP_KERNEL);
+ if (!pi) {
+ *error = "queue-length ps: Error allocating path information";
+ return -ENOMEM;
+ }
+
+ pi->path = path;
+ pi->repeat_count = repeat_count;
+ atomic_set(&pi->qlen, 0);
+
+ path->pscontext = pi;
+
+ spin_lock_irqsave(&s->lock, flags);
+ list_add_tail(&pi->list, &s->valid_paths);
+ spin_unlock_irqrestore(&s->lock, flags);
+
+ return 0;
+}
+
+static void ql_fail_path(struct path_selector *ps, struct dm_path *path)
+{
+ struct selector *s = ps->context;
+ struct path_info *pi = path->pscontext;
+ unsigned long flags;
+
+ spin_lock_irqsave(&s->lock, flags);
+ list_move(&pi->list, &s->failed_paths);
+ spin_unlock_irqrestore(&s->lock, flags);
+}
+
+static int ql_reinstate_path(struct path_selector *ps, struct dm_path *path)
+{
+ struct selector *s = ps->context;
+ struct path_info *pi = path->pscontext;
+ unsigned long flags;
+
+ spin_lock_irqsave(&s->lock, flags);
+ list_move_tail(&pi->list, &s->valid_paths);
+ spin_unlock_irqrestore(&s->lock, flags);
+
+ return 0;
+}
+
+/*
+ * Select a path having the minimum number of in-flight I/Os
+ */
+static struct dm_path *ql_select_path(struct path_selector *ps, size_t nr_bytes)
+{
+ struct selector *s = ps->context;
+ struct path_info *pi = NULL, *best = NULL;
+ struct dm_path *ret = NULL;
+ unsigned long flags;
+
+ spin_lock_irqsave(&s->lock, flags);
+ if (list_empty(&s->valid_paths))
+ goto out;
+
+ list_for_each_entry(pi, &s->valid_paths, list) {
+ if (!best ||
+ (atomic_read(&pi->qlen) < atomic_read(&best->qlen)))
+ best = pi;
+
+ if (!atomic_read(&best->qlen))
+ break;
+ }
+
+ if (!best)
+ goto out;
+
+ /* Move most recently used to least preferred to evenly balance. */
+ list_move_tail(&best->list, &s->valid_paths);
+
+ ret = best->path;
+out:
+ spin_unlock_irqrestore(&s->lock, flags);
+ return ret;
+}
+
+static int ql_start_io(struct path_selector *ps, struct dm_path *path,
+ size_t nr_bytes)
+{
+ struct path_info *pi = path->pscontext;
+
+ atomic_inc(&pi->qlen);
+
+ return 0;
+}
+
+static int ql_end_io(struct path_selector *ps, struct dm_path *path,
+ size_t nr_bytes, u64 start_time)
+{
+ struct path_info *pi = path->pscontext;
+
+ atomic_dec(&pi->qlen);
+
+ return 0;
+}
+
+static struct path_selector_type ql_ps = {
+ .name = "queue-length",
+ .module = THIS_MODULE,
+ .table_args = 1,
+ .info_args = 1,
+ .create = ql_create,
+ .destroy = ql_destroy,
+ .status = ql_status,
+ .add_path = ql_add_path,
+ .fail_path = ql_fail_path,
+ .reinstate_path = ql_reinstate_path,
+ .select_path = ql_select_path,
+ .start_io = ql_start_io,
+ .end_io = ql_end_io,
+};
+
+static int __init dm_ql_init(void)
+{
+ int r = dm_register_path_selector(&ql_ps);
+
+ if (r < 0)
+ DMERR("register failed %d", r);
+
+ DMINFO("version " QL_VERSION " loaded");
+
+ return r;
+}
+
+static void __exit dm_ql_exit(void)
+{
+ int r = dm_unregister_path_selector(&ql_ps);
+
+ if (r < 0)
+ DMERR("unregister failed %d", r);
+}
+
+module_init(dm_ql_init);
+module_exit(dm_ql_exit);
+
+MODULE_AUTHOR("Stefan Bader <Stefan.Bader at de.ibm.com>");
+MODULE_DESCRIPTION(
+ "(C) Copyright IBM Corp. 2004,2005 All Rights Reserved.\n"
+ DM_NAME " path selector to balance the number of in-flight I/Os"
+);
+MODULE_LICENSE("GPL");