| 1 | // SPDX-License-Identifier: GPL-2.0-or-later |
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| 2 | /* |
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| 3 | * Copyright (c) 2022-2024 Oracle. All Rights Reserved. |
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| 4 | * Author: Darrick J. Wong <djwong@kernel.org> |
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| 5 | */ |
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| 6 | #ifndef XFS_HOOKS_H_ |
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| 7 | #define XFS_HOOKS_H_ |
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| 8 | |
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| 9 | #ifdef CONFIG_XFS_LIVE_HOOKS |
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| 10 | struct xfs_hooks { |
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| 11 | struct blocking_notifier_head head; |
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| 12 | }; |
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| 13 | |
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| 14 | /* |
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| 15 | * If jump labels are enabled in Kconfig, the static key uses nop sleds and |
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| 16 | * code patching to eliminate the overhead of taking the rwsem in |
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| 17 | * blocking_notifier_call_chain when there are no hooks configured. If not, |
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| 18 | * the static key per-call overhead is an atomic read. Most arches that can |
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| 19 | * handle XFS also support jump labels. |
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| 20 | * |
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| 21 | * Note: Patching the kernel code requires taking the cpu hotplug lock. Other |
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| 22 | * parts of the kernel allocate memory with that lock held, which means that |
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| 23 | * XFS callers cannot hold any locks that might be used by memory reclaim or |
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| 24 | * writeback when calling the static_branch_{inc,dec} functions. |
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| 25 | */ |
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| 26 | # define DEFINE_STATIC_XFS_HOOK_SWITCH(name) \ |
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| 27 | static DEFINE_STATIC_KEY_FALSE(name) |
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| 28 | # define xfs_hooks_switch_on(name) static_branch_inc(name) |
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| 29 | # define xfs_hooks_switch_off(name) static_branch_dec(name) |
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| 30 | # define xfs_hooks_switched_on(name) static_branch_unlikely(name) |
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| 31 | |
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| 32 | struct xfs_hook { |
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| 33 | /* This must come at the start of the structure. */ |
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| 34 | struct notifier_block nb; |
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| 35 | }; |
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| 36 | |
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| 37 | typedef int (*xfs_hook_fn_t)(struct xfs_hook *hook, unsigned long action, |
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| 38 | void *data); |
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| 39 | |
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| 40 | void xfs_hooks_init(struct xfs_hooks *chain); |
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| 41 | int xfs_hooks_add(struct xfs_hooks *chain, struct xfs_hook *hook); |
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| 42 | void xfs_hooks_del(struct xfs_hooks *chain, struct xfs_hook *hook); |
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| 43 | int xfs_hooks_call(struct xfs_hooks *chain, unsigned long action, |
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| 44 | void *priv); |
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| 45 | |
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| 46 | static inline void xfs_hook_setup(struct xfs_hook *hook, notifier_fn_t fn) |
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| 47 | { |
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| 48 | hook->nb.notifier_call = fn; |
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| 49 | hook->nb.priority = 0; |
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| 50 | } |
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| 51 | |
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| 52 | #else |
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| 53 | |
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| 54 | struct xfs_hooks { /* empty */ }; |
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| 55 | |
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| 56 | # define DEFINE_STATIC_XFS_HOOK_SWITCH(name) |
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| 57 | # define xfs_hooks_switch_on(name) ((void)0) |
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| 58 | # define xfs_hooks_switch_off(name) ((void)0) |
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| 59 | # define xfs_hooks_switched_on(name) (false) |
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| 60 | |
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| 61 | # define xfs_hooks_init(chain) ((void)0) |
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| 62 | # define xfs_hooks_call(chain, val, priv) (NOTIFY_DONE) |
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| 63 | #endif |
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| 64 | |
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| 65 | #endif /* XFS_HOOKS_H_ */ |
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| 66 | |
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