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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-11 08:27:49 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-11 08:27:49 +0000
commitace9429bb58fd418f0c81d4c2835699bddf6bde6 (patch)
treeb2d64bc10158fdd5497876388cd68142ca374ed3 /drivers/md/dm-path-selector.h
parentInitial commit. (diff)
downloadlinux-ace9429bb58fd418f0c81d4c2835699bddf6bde6.tar.xz
linux-ace9429bb58fd418f0c81d4c2835699bddf6bde6.zip
Adding upstream version 6.6.15.upstream/6.6.15
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'drivers/md/dm-path-selector.h')
-rw-r--r--drivers/md/dm-path-selector.h107
1 files changed, 107 insertions, 0 deletions
diff --git a/drivers/md/dm-path-selector.h b/drivers/md/dm-path-selector.h
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+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (C) 2003 Sistina Software.
+ * Copyright (C) 2004 Red Hat, Inc. All rights reserved.
+ *
+ * Module Author: Heinz Mauelshagen
+ *
+ * This file is released under the GPL.
+ *
+ * Path-Selector registration.
+ */
+
+#ifndef DM_PATH_SELECTOR_H
+#define DM_PATH_SELECTOR_H
+
+#include <linux/device-mapper.h>
+
+#include "dm-mpath.h"
+
+/*
+ * We provide an abstraction for the code that chooses which path
+ * to send some io down.
+ */
+struct path_selector_type;
+struct path_selector {
+ struct path_selector_type *type;
+ void *context;
+};
+
+/*
+ * If a path selector uses this flag, a high resolution timer is used
+ * (via ktime_get_ns) to account for IO start time in BIO-based mpath.
+ * This improves performance of some path selectors (i.e. HST), in
+ * exchange for slightly higher overhead when submitting the BIO.
+ * The extra cost is usually offset by improved path selection for
+ * some benchmarks.
+ *
+ * This has no effect for request-based mpath, since it already uses a
+ * higher precision timer by default.
+ */
+#define DM_PS_USE_HR_TIMER 0x00000001
+#define dm_ps_use_hr_timer(type) ((type)->features & DM_PS_USE_HR_TIMER)
+
+/* Information about a path selector type */
+struct path_selector_type {
+ char *name;
+ struct module *module;
+
+ unsigned int features;
+ unsigned int table_args;
+ unsigned int info_args;
+
+ /*
+ * Constructs a path selector object, takes custom arguments
+ */
+ int (*create)(struct path_selector *ps, unsigned int argc, char **argv);
+ void (*destroy)(struct path_selector *ps);
+
+ /*
+ * Add an opaque path object, along with some selector specific
+ * path args (eg, path priority).
+ */
+ int (*add_path)(struct path_selector *ps, struct dm_path *path,
+ int argc, char **argv, char **error);
+
+ /*
+ * Chooses a path for this io, if no paths are available then
+ * NULL will be returned.
+ */
+ struct dm_path *(*select_path)(struct path_selector *ps, size_t nr_bytes);
+
+ /*
+ * Notify the selector that a path has failed.
+ */
+ void (*fail_path)(struct path_selector *ps, struct dm_path *p);
+
+ /*
+ * Ask selector to reinstate a path.
+ */
+ int (*reinstate_path)(struct path_selector *ps, struct dm_path *p);
+
+ /*
+ * Table content based on parameters added in ps_add_path_fn
+ * or path selector status
+ */
+ int (*status)(struct path_selector *ps, struct dm_path *path,
+ status_type_t type, char *result, unsigned int maxlen);
+
+ int (*start_io)(struct path_selector *ps, struct dm_path *path,
+ size_t nr_bytes);
+ int (*end_io)(struct path_selector *ps, struct dm_path *path,
+ size_t nr_bytes, u64 start_time);
+};
+
+/* Register a path selector */
+int dm_register_path_selector(struct path_selector_type *type);
+
+/* Unregister a path selector */
+int dm_unregister_path_selector(struct path_selector_type *type);
+
+/* Returns a registered path selector type */
+struct path_selector_type *dm_get_path_selector(const char *name);
+
+/* Releases a path selector */
+void dm_put_path_selector(struct path_selector_type *pst);
+
+#endif