// SPDX-License-Identifier: GPL-2.0-only /* * Frontswap frontend * * This code provides the generic "frontend" layer to call a matching * "backend" driver implementation of frontswap. See * Documentation/vm/frontswap.rst for more information. * * Copyright (C) 2009-2012 Oracle Corp. All rights reserved. * Author: Dan Magenheimer */ #include #include #include #include #include #include #include #include DEFINE_STATIC_KEY_FALSE(frontswap_enabled_key); /* * frontswap_ops are added by frontswap_register_ops, and provide the * frontswap "backend" implementation functions. Multiple implementations * may be registered, but implementations can never deregister. This * is a simple singly-linked list of all registered implementations. */ static struct frontswap_ops *frontswap_ops __read_mostly; #define for_each_frontswap_ops(ops) \ for ((ops) = frontswap_ops; (ops); (ops) = (ops)->next) /* * If enabled, frontswap_store will return failure even on success. As * a result, the swap subsystem will always write the page to swap, in * effect converting frontswap into a writethrough cache. In this mode, * there is no direct reduction in swap writes, but a frontswap backend * can unilaterally "reclaim" any pages in use with no data loss, thus * providing increases control over maximum memory usage due to frontswap. */ static bool frontswap_writethrough_enabled __read_mostly; /* * If enabled, the underlying tmem implementation is capable of doing * exclusive gets, so frontswap_load, on a successful tmem_get must * mark the page as no longer in frontswap AND mark it dirty. */ static bool frontswap_tmem_exclusive_gets_enabled __read_mostly; #ifdef CONFIG_DEBUG_FS /* * Counters available via /sys/kernel/debug/frontswap (if debugfs is * properly configured). These are for information only so are not protected * against increment races. */ static u64 frontswap_loads; static u64 frontswap_succ_stores; static u64 frontswap_failed_stores; static u64 frontswap_invalidates; static inline void inc_frontswap_loads(void) { frontswap_loads++; } static inline void inc_frontswap_succ_stores(void) { frontswap_succ_stores++; } static inline void inc_frontswap_failed_stores(void) { frontswap_failed_stores++; } static inline void inc_frontswap_invalidates(void) { frontswap_invalidates++; } #else static inline void inc_frontswap_loads(void) { } static inline void inc_frontswap_succ_stores(void) { } static inline void inc_frontswap_failed_stores(void) { } static inline void inc_frontswap_invalidates(void) { } #endif /* * Due to the asynchronous nature of the backends loading potentially * _after_ the swap system has been activated, we have chokepoints * on all frontswap functions to not call the backend until the backend * has registered. * * This would not guards us against the user deciding to call swapoff right as * we are calling the backend to initialize (so swapon is in action). * Fortunatly for us, the swapon_mutex has been taked by the callee so we are * OK. The other scenario where calls to frontswap_store (called via * swap_writepage) is racing with frontswap_invalidate_area (called via * swapoff) is again guarded by the swap subsystem. * * While no backend is registered all calls to frontswap_[store|load| * invalidate_area|invalidate_page] are ignored or fail. * * The time between the backend being registered and the swap file system * calling the backend (via the frontswap_* functions) is indeterminate as * frontswap_ops is not atomic_t (or a value guarded by a spinlock). * That is OK as we are comfortable missing some of these calls to the newly * registered backend. * * Obviously the opposite (unloading the backend) must be done after all * the frontswap_[store|load|invalidate_area|invalidate_pag

#ifndef XFS_DISCARD_H
#define XFS_DISCARD_H 1

struct fstrim_range;
struct list_head;

extern int	xfs_ioc_trim(struct xfs_mount *, struct fstrim_range __user *);

#endif /* XFS_DISCARD_H */

ap_curr_pages(void) { unsigned long totalpages = 0; spin_lock(&swap_lock); totalpages = __frontswap_curr_pages(); spin_unlock(&swap_lock); return totalpages; } EXPORT_SYMBOL(frontswap_curr_pages); static int __init init_frontswap(void) { #ifdef CONFIG_DEBUG_FS struct dentry *root = debugfs_create_dir("frontswap", NULL); if (root == NULL) return -ENXIO; debugfs_create_u64("loads", 0444, root, &frontswap_loads); debugfs_create_u64("succ_stores", 0444, root, &frontswap_succ_stores); debugfs_create_u64("failed_stores", 0444, root, &frontswap_failed_stores); debugfs_create_u64("invalidates", 0444, root, &frontswap_invalidates); #endif return 0; } module_init(init_frontswap);