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1// SPDX-License-Identifier: GPL-2.0-or-later2/*3 * Copyright (c) 2022-2024 Oracle. All Rights Reserved.4 * Author: Darrick J. Wong <djwong@kernel.org>5 */6#ifndef XFS_HOOKS_H_7#define XFS_HOOKS_H_8 9#ifdef CONFIG_XFS_LIVE_HOOKS10struct xfs_hooks {11 struct blocking_notifier_head head;12};13 14/*15 * If jump labels are enabled in Kconfig, the static key uses nop sleds and16 * code patching to eliminate the overhead of taking the rwsem in17 * blocking_notifier_call_chain when there are no hooks configured. If not,18 * the static key per-call overhead is an atomic read. Most arches that can19 * handle XFS also support jump labels.20 *21 * Note: Patching the kernel code requires taking the cpu hotplug lock. Other22 * parts of the kernel allocate memory with that lock held, which means that23 * XFS callers cannot hold any locks that might be used by memory reclaim or24 * writeback when calling the static_branch_{inc,dec} functions.25 */26# define DEFINE_STATIC_XFS_HOOK_SWITCH(name) \27 static DEFINE_STATIC_KEY_FALSE(name)28# define xfs_hooks_switch_on(name) static_branch_inc(name)29# define xfs_hooks_switch_off(name) static_branch_dec(name)30# define xfs_hooks_switched_on(name) static_branch_unlikely(name)31 32struct xfs_hook {33 /* This must come at the start of the structure. */34 struct notifier_block nb;35};36 37typedef int (*xfs_hook_fn_t)(struct xfs_hook *hook, unsigned long action,38 void *data);39 40void xfs_hooks_init(struct xfs_hooks *chain);41int xfs_hooks_add(struct xfs_hooks *chain, struct xfs_hook *hook);42void xfs_hooks_del(struct xfs_hooks *chain, struct xfs_hook *hook);43int xfs_hooks_call(struct xfs_hooks *chain, unsigned long action,44 void *priv);45 46static inline void xfs_hook_setup(struct xfs_hook *hook, notifier_fn_t fn)47{48 hook->nb.notifier_call = fn;49 hook->nb.priority = 0;50}51 52#else53 54struct xfs_hooks { /* empty */ };55 56# define DEFINE_STATIC_XFS_HOOK_SWITCH(name)57# define xfs_hooks_switch_on(name) ((void)0)58# define xfs_hooks_switch_off(name) ((void)0)59# define xfs_hooks_switched_on(name) (false)60 61# define xfs_hooks_init(chain) ((void)0)62# define xfs_hooks_call(chain, val, priv) (NOTIFY_DONE)63#endif64 65#endif /* XFS_HOOKS_H_ */66