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 | |