| Author | Tokens | Token Proportion | Commits | Commit Proportion |
|---|---|---|---|---|
| Dan Magenheimer | 849 | 52.60% | 3 | 13.04% |
| Dan Streetman | 375 | 23.23% | 3 | 13.04% |
| Sasha Levin | 237 | 14.68% | 6 | 26.09% |
| Bob Liu | 44 | 2.73% | 1 | 4.35% |
| Konrad Rzeszutek Wilk | 37 | 2.29% | 2 | 8.70% |
| Vlastimil Babka | 34 | 2.11% | 1 | 4.35% |
| MinChan Kim | 26 | 1.61% | 1 | 4.35% |
| Joe Perches | 4 | 0.25% | 1 | 4.35% |
| Seth Jennings | 3 | 0.19% | 1 | 4.35% |
| Duan Zhenzhong | 2 | 0.12% | 1 | 4.35% |
| Mike Rapoport | 1 | 0.06% | 1 | 4.35% |
| Akinobu Mita | 1 | 0.06% | 1 | 4.35% |
| Wanpeng Li | 1 | 0.06% | 1 | 4.35% |
| Total | 1614 | 23 |
/* * 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 * * This work is licensed under the terms of the GNU GPL, version 2. */ #include <linux/mman.h> #include <linux/swap.h> #include <linux/swapops.h> #include <linux/security.h> #include <linux/module.h> #include <linux/debugfs.h> #include <linux/frontswap.h> #include <linux/swapfile.h> 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_page] start * ignoring or failing the requests. However, there is currently no way * to unload a backend once it is registered. */ /* * Register operations for frontswap */ void frontswap_register_ops(struct frontswap_ops *ops) { DECLARE_BITMAP(a, MAX_SWAPFILES); DECLARE_BITMAP(b, MAX_SWAPFILES); struct swap_info_struct *si; unsigned int i; bitmap_zero(a, MAX_SWAPFILES); bitmap_zero(b, MAX_SWAPFILES); spin_lock(&swap_lock); plist_for_each_entry(si, &swap_active_head, list) { if (!WARN_ON(!si->frontswap_map)) set_bit(si->type, a); } spin_unlock(&swap_lock); /* the new ops needs to know the currently active swap devices */ for_each_set_bit(i, a, MAX_SWAPFILES) ops->init(i); /* * Setting frontswap_ops must happen after the ops->init() calls * above; cmpxchg implies smp_mb() which will ensure the init is * complete at this point. */ do { ops->next = frontswap_ops; } while (cmpxchg(&frontswap_ops, ops->next, ops) != ops->next); static_branch_inc(&frontswap_enabled_key); spin_lock(&swap_lock); plist_for_each_entry(si, &swap_active_head, list) { if (si->frontswap_map) set_bit(si->type, b); } spin_unlock(&swap_lock); /* * On the very unlikely chance that a swap device was added or * removed between setting the "a" list bits and the ops init * calls, we re-check and do init or invalidate for any changed * bits. */ if (unlikely(!bitmap_equal(a, b, MAX_SWAPFILES))) { for (i = 0; i < MAX_SWAPFILES; i++) { if (!test_bit(i, a) && test_bit(i, b)) ops->init(i); else if (test_bit(i, a) && !test_bit(i, b)) ops->invalidate_area(i); } } } EXPORT_SYMBOL(frontswap_register_ops); /* * Enable/disable frontswap writethrough (see above). */ void frontswap_writethrough(bool enable) { frontswap_writethrough_enabled = enable; } EXPORT_SYMBOL(frontswap_writethrough); /* * Enable/disable frontswap exclusive gets (see above). */ void frontswap_tmem_exclusive_gets(bool enable) { frontswap_tmem_exclusive_gets_enabled = enable; } EXPORT_SYMBOL(frontswap_tmem_exclusive_gets); /* * Called when a swap device is swapon'd. */ void __frontswap_init(unsigned type, unsigned long *map) { struct swap_info_struct *sis = swap_info[type]; struct frontswap_ops *ops; VM_BUG_ON(sis == NULL); /* * p->frontswap is a bitmap that we MUST have to figure out which page * has gone in frontswap. Without it there is no point of continuing. */ if (WARN_ON(!map)) return; /* * Irregardless of whether the frontswap backend has been loaded * before this function or it will be later, we _MUST_ have the * p->frontswap set to something valid to work properly. */ frontswap_map_set(sis, map); for_each_frontswap_ops(ops) ops->init(type); } EXPORT_SYMBOL(__frontswap_init); bool __frontswap_test(struct swap_info_struct *sis, pgoff_t offset) { if (sis->frontswap_map) return test_bit(offset, sis->frontswap_map); return false; } EXPORT_SYMBOL(__frontswap_test); static inline void __frontswap_set(struct swap_info_struct *sis, pgoff_t offset) { set_bit(offset, sis->frontswap_map); atomic_inc(&sis->frontswap_pages); } static inline void __frontswap_clear(struct swap_info_struct *sis, pgoff_t offset) { clear_bit(offset, sis->frontswap_map); atomic_dec(&sis->frontswap_pages); } /* * "Store" data from a page to frontswap and associate it with the page's * swaptype and offset. Page must be locked and in the swap cache. * If frontswap already contains a page with matching swaptype and * offset, the frontswap implementation may either overwrite the data and * return success or invalidate the page from frontswap and return failure. */ int __frontswap_store(struct page *page) { int ret = -1; swp_entry_t entry = { .val = page_private(page), }; int type = swp_type(entry); struct swap_info_struct *sis = swap_info[type]; pgoff_t offset = swp_offset(entry); struct frontswap_ops *ops; VM_BUG_ON(!frontswap_ops); VM_BUG_ON(!PageLocked(page)); VM_BUG_ON(sis == NULL); /* * If a dup, we must remove the old page first; we can't leave the * old page no matter if the store of the new page succeeds or fails, * and we can't rely on the new page replacing the old page as we may * not store to the same implementation that contains the old page. */ if (__frontswap_test(sis, offset)) { __frontswap_clear(sis, offset); for_each_frontswap_ops(ops) ops->invalidate_page(type, offset); } /* Try to store in each implementation, until one succeeds. */ for_each_frontswap_ops(ops) { ret = ops->store(type, offset, page); if (!ret) /* successful store */ break; } if (ret == 0) { __frontswap_set(sis, offset); inc_frontswap_succ_stores(); } else { inc_frontswap_failed_stores(); } if (frontswap_writethrough_enabled) /* report failure so swap also writes to swap device */ ret = -1; return ret; } EXPORT_SYMBOL(__frontswap_store); /* * "Get" data from frontswap associated with swaptype and offset that were * specified when the data was put to frontswap and use it to fill the * specified page with data. Page must be locked and in the swap cache. */ int __frontswap_load(struct page *page) { int ret = -1; swp_entry_t entry = { .val = page_private(page), }; int type = swp_type(entry); struct swap_info_struct *sis = swap_info[type]; pgoff_t offset = swp_offset(entry); struct frontswap_ops *ops; VM_BUG_ON(!frontswap_ops); VM_BUG_ON(!PageLocked(page)); VM_BUG_ON(sis == NULL); if (!__frontswap_test(sis, offset)) return -1; /* Try loading from each implementation, until one succeeds. */ for_each_frontswap_ops(ops) { ret = ops->load(type, offset, page); if (!ret) /* successful load */ break; } if (ret == 0) { inc_frontswap_loads(); if (frontswap_tmem_exclusive_gets_enabled) { SetPageDirty(page); __frontswap_clear(sis, offset); } } return ret; } EXPORT_SYMBOL(__frontswap_load); /* * Invalidate any data from frontswap associated with the specified swaptype * and offset so that a subsequent "get" will fail. */ void __frontswap_invalidate_page(unsigned type, pgoff_t offset) { struct swap_info_struct *sis = swap_info[type]; struct frontswap_ops *ops; VM_BUG_ON(!frontswap_ops); VM_BUG_ON(sis == NULL); if (!__frontswap_test(sis, offset)) return; for_each_frontswap_ops(ops) ops->invalidate_page(type, offset); __frontswap_clear(sis, offset); inc_frontswap_invalidates(); } EXPORT_SYMBOL(__frontswap_invalidate_page); /* * Invalidate all data from frontswap associated with all offsets for the * specified swaptype. */ void __frontswap_invalidate_area(unsigned type) { struct swap_info_struct *sis = swap_info[type]; struct frontswap_ops *ops; VM_BUG_ON(!frontswap_ops); VM_BUG_ON(sis == NULL); if (sis->frontswap_map == NULL) return; for_each_frontswap_ops(ops) ops->invalidate_area(type); atomic_set(&sis->frontswap_pages, 0); bitmap_zero(sis->frontswap_map, sis->max); } EXPORT_SYMBOL(__frontswap_invalidate_area); static unsigned long __frontswap_curr_pages(void) { unsigned long totalpages = 0; struct swap_info_struct *si = NULL; assert_spin_locked(&swap_lock); plist_for_each_entry(si, &swap_active_head, list) totalpages += atomic_read(&si->frontswap_pages); return totalpages; } static int __frontswap_unuse_pages(unsigned long total, unsigned long *unused, int *swapid) { int ret = -EINVAL; struct swap_info_struct *si = NULL; int si_frontswap_pages; unsigned long total_pages_to_unuse = total; unsigned long pages = 0, pages_to_unuse = 0; assert_spin_locked(&swap_lock); plist_for_each_entry(si, &swap_active_head, list) { si_frontswap_pages = atomic_read(&si->frontswap_pages); if (total_pages_to_unuse < si_frontswap_pages) { pages = pages_to_unuse = total_pages_to_unuse; } else { pages = si_frontswap_pages; pages_to_unuse = 0; /* unuse all */ } /* ensure there is enough RAM to fetch pages from frontswap */ if (security_vm_enough_memory_mm(current->mm, pages)) { ret = -ENOMEM; continue; } vm_unacct_memory(pages); *unused = pages_to_unuse; *swapid = si->type; ret = 0; break; } return ret; } /* * Used to check if it's necessory and feasible to unuse pages. * Return 1 when nothing to do, 0 when need to shink pages, * error code when there is an error. */ static int __frontswap_shrink(unsigned long target_pages, unsigned long *pages_to_unuse, int *type) { unsigned long total_pages = 0, total_pages_to_unuse; assert_spin_locked(&swap_lock); total_pages = __frontswap_curr_pages(); if (total_pages <= target_pages) { /* Nothing to do */ *pages_to_unuse = 0; return 1; } total_pages_to_unuse = total_pages - target_pages; return __frontswap_unuse_pages(total_pages_to_unuse, pages_to_unuse, type); } /* * Frontswap, like a true swap device, may unnecessarily retain pages * under certain circumstances; "shrink" frontswap is essentially a * "partial swapoff" and works by calling try_to_unuse to attempt to * unuse enough frontswap pages to attempt to -- subject to memory * constraints -- reduce the number of pages in frontswap to the * number given in the parameter target_pages. */ void frontswap_shrink(unsigned long target_pages) { unsigned long pages_to_unuse = 0; int uninitialized_var(type), ret; /* * we don't want to hold swap_lock while doing a very * lengthy try_to_unuse, but swap_list may change * so restart scan from swap_active_head each time */ spin_lock(&swap_lock); ret = __frontswap_shrink(target_pages, &pages_to_unuse, &type); spin_unlock(&swap_lock); if (ret == 0) try_to_unuse(type, true, pages_to_unuse); return; } EXPORT_SYMBOL(frontswap_shrink); /* * Count and return the number of frontswap pages across all * swap devices. This is exported so that backend drivers can * determine current usage without reading debugfs. */ unsigned long frontswap_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);
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