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// SPDX-License-Identifier: GPL-2.0-or-later
/*
* Copyright (c) 2022-2024 Oracle. All Rights Reserved.
* Author: Darrick J. Wong <djwong@kernel.org>
*/
#ifndef XFS_HOOKS_H_
#define XFS_HOOKS_H_
#ifdef CONFIG_XFS_LIVE_HOOKS
struct xfs_hooks {
struct blocking_notifier_head head;
};
/*
* If jump labels are enabled in Kconfig, the static key uses nop sleds and
* code patching to eliminate the overhead of taking the rwsem in
* blocking_notifier_call_chain when there are no hooks configured. If not,
* the static key per-call overhead is an atomic read. Most arches that can
* handle XFS also support jump labels.
*
* Note: Patching the kernel code requires taking the cpu hotplug lock. Other
* parts of the kernel allocate memory with that lock held, which means that
* XFS callers cannot hold any locks that might be used by memory reclaim or
* writeback when calling the static_branch_{inc,dec} functions.
*/
# define DEFINE_STATIC_XFS_HOOK_SWITCH(name) \
static DEFINE_STATIC_KEY_FALSE(name)
# define xfs_hooks_switch_on(name) static_branch_inc(name)
# define xfs_hooks_switch_off(name) static_branch_dec(name)
# define xfs_hooks_switched_on(name) static_branch_unlikely(name)
struct xfs_hook {
/* This must come at the start of the structure. */
struct notifier_block nb;
};
typedef int (*xfs_hook_fn_t)(struct xfs_hook *hook, unsigned long action,
void *data);
void xfs_hooks_init(struct xfs_hooks *chain);
int xfs_hooks_add(struct xfs_hooks *chain, struct xfs_hook *hook);
void xfs_hooks_del(struct xfs_hooks *chain, struct xfs_hook *hook);
int xfs_hooks_call(struct xfs_hooks *chain, unsigned long action,
void *priv);
static inline void xfs_hook_setup(struct xfs_hook *hook, notifier_fn_t fn)
{
hook->nb.notifier_call = fn;
hook->nb.priority = 0;
}
#else
struct xfs_hooks { /* empty */ };
# define DEFINE_STATIC_XFS_HOOK_SWITCH(name)
# define xfs_hooks_switch_on(name) ((void)0)
# define xfs_hooks_switch_off(name) ((void)0)
# define xfs_hooks_switched_on(name) (false)
# define xfs_hooks_init(chain) ((void)0)
# define xfs_hooks_call(chain, val, priv) (NOTIFY_DONE)
#endif
#endif /* XFS_HOOKS_H_ */
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