Add initial framework for libmultipath. libmultipath is a library for multipath-capable block drivers, such as NVMe. The main function is to support path management, path selection, and failover handling.
Basic support to add and remove the head structure - mpath_head - is included. This main purpose of this structure is to manage available paths and path selection. It is quite similar to the multipath functionality in nvme_ns_head. It also manages the multipath gendisk. Each path is represented by the mpath_device structure. It should hold a pointer to the per-path gendisk and also a list element for all siblings of paths. For NVMe, there would be a mpath_device per nvme_ns. All the libmultipath code is more or less taken from drivers/nvme/host/multipath.c, which was originally authored by Christoph Hellwig <[email protected]>. Signed-off-by: John Garry <[email protected]> --- include/linux/multipath.h | 28 +++++++++++++++ lib/Kconfig | 6 ++++ lib/Makefile | 2 ++ lib/multipath.c | 74 +++++++++++++++++++++++++++++++++++++++ 4 files changed, 110 insertions(+) create mode 100644 include/linux/multipath.h create mode 100644 lib/multipath.c diff --git a/include/linux/multipath.h b/include/linux/multipath.h new file mode 100644 index 0000000000000..e98b4b241020a --- /dev/null +++ b/include/linux/multipath.h @@ -0,0 +1,28 @@ + +#ifndef _LIBMULTIPATH_H +#define _LIBMULTIPATH_H + +#include <linux/blkdev.h> +#include <linux/srcu.h> + +struct mpath_device { + struct list_head siblings; + struct gendisk *disk; +}; + +struct mpath_head { + struct srcu_struct srcu; + struct list_head dev_list; /* list of all mpath_devs */ + struct mutex lock; + + refcount_t refcount; + + struct mpath_device __rcu *current_path[MAX_NUMNODES]; +}; + +int mpath_get_head(struct mpath_head *mpath_head); +void mpath_put_head(struct mpath_head *mpath_head); +int mpath_head_init(struct mpath_head *mpath_head); +void mpath_head_uninit(struct mpath_head *mpath_head); + +#endif // _LIBMULTIPATH_H diff --git a/lib/Kconfig b/lib/Kconfig index 55748b68714e0..d0258bef374a1 100644 --- a/lib/Kconfig +++ b/lib/Kconfig @@ -636,3 +636,9 @@ config UNION_FIND config MIN_HEAP bool + +config LIBMULTIPATH + bool "MULTIPATH BLOCK DRIVER LIBRARY" + depends on BLOCK + help + If you say yes here then you get a multipath lib for block drivers diff --git a/lib/Makefile b/lib/Makefile index 7f75cc6edf94a..7ba5e13be4171 100644 --- a/lib/Makefile +++ b/lib/Makefile @@ -334,3 +334,5 @@ CONTEXT_ANALYSIS_test_context-analysis.o := y obj-$(CONFIG_CONTEXT_ANALYSIS_TEST) += test_context-analysis.o subdir-$(CONFIG_FORTIFY_SOURCE) += test_fortify + +obj-$(CONFIG_LIBMULTIPATH) += multipath.o diff --git a/lib/multipath.c b/lib/multipath.c new file mode 100644 index 0000000000000..009d4bb875c6f --- /dev/null +++ b/lib/multipath.c @@ -0,0 +1,74 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Copyright (c) 2017-2018 Christoph Hellwig. + * Copyright (c) 2026 Oracle and/or its affiliates. + */ +#include <linux/module.h> +#include <linux/multipath.h> + +static struct workqueue_struct *mpath_wq; + +int mpath_get_head(struct mpath_head *mpath_head) +{ + if (!refcount_inc_not_zero(&mpath_head->refcount)) + return -ENXIO; + return 0; +} +EXPORT_SYMBOL_GPL(mpath_get_head); + +static void mpath_head_cleanup(struct mpath_head *mpath_head) +{ + cleanup_srcu_struct(&mpath_head->srcu); +} + +void mpath_put_head(struct mpath_head *mpath_head) +{ + refcount_t *refcount = &mpath_head->refcount; + + if (refcount_dec_and_test(refcount)) { + mpath_head_cleanup(mpath_head); + wake_up_var(refcount); + } +} +EXPORT_SYMBOL_GPL(mpath_put_head); + +void mpath_head_uninit(struct mpath_head *mpath_head) +{ + refcount_t *refcount = &mpath_head->refcount; + + if (refcount_dec_and_test(refcount)) { + mpath_head_cleanup(mpath_head); + } else { + wait_var_event(refcount, !refcount_read(refcount)); + } +} +EXPORT_SYMBOL_GPL(mpath_head_uninit); + +int mpath_head_init(struct mpath_head *mpath_head) +{ + INIT_LIST_HEAD(&mpath_head->dev_list); + mutex_init(&mpath_head->lock); + refcount_set(&mpath_head->refcount, 1); + + return init_srcu_struct(&mpath_head->srcu); +} +EXPORT_SYMBOL_GPL(mpath_head_init); + +static int __init mpath_init(void) +{ + mpath_wq = alloc_workqueue("mpath-wq", + WQ_UNBOUND | WQ_MEM_RECLAIM | WQ_SYSFS, 0); + if (!mpath_wq) + return -ENOMEM; + return 0; +} + +static void __exit mpath_exit(void) +{ + destroy_workqueue(mpath_wq); +} + +module_init(mpath_init); +module_exit(mpath_exit); +MODULE_LICENSE("GPL"); +MODULE_DESCRIPTION("libmultipath"); -- 2.43.7
