1 // SPDX-License-Identifier: GPL-2.0-or-later 2 /* 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_HOOKS 10 struct 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 and 16 * code patching to eliminate the overhead of taking the rwsem in 17 * 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 can 19 * handle XFS also support jump labels. 20 * 21 * Note: Patching the kernel code requires taking the cpu hotplug lock. Other 22 * parts of the kernel allocate memory with that lock held, which means that 23 * XFS callers cannot hold any locks that might be used by memory reclaim or 24 * 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 32 struct xfs_hook { 33 /* This must come at the start of the structure. */ 34 struct notifier_block nb; 35 }; 36 37 typedef int (*xfs_hook_fn_t)(struct xfs_hook *hook, unsigned long action, 38 void *data); 39 40 void xfs_hooks_init(struct xfs_hooks *chain); 41 int xfs_hooks_add(struct xfs_hooks *chain, struct xfs_hook *hook); 42 void xfs_hooks_del(struct xfs_hooks *chain, struct xfs_hook *hook); 43 int xfs_hooks_call(struct xfs_hooks *chain, unsigned long action, 44 void *priv); 45 46 static 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 #else 53 54 struct 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 #endif 64 65 #endif /* XFS_HOOKS_H_ */ 66