From c3ba9698152b17fdc2c7cd0f7cbeb571e3367e9d Mon Sep 17 00:00:00 2001 From: Dan Magenheimer Date: Mon, 9 Apr 2012 17:06:54 -0600 Subject: mm: frontswap: add frontswap header file Frontswap is the alter ego of cleancache, the "yang" to cleancache's "yin"... and more precisely frontswap is the provider of anonymous pages to transcendent memory to nicely complement cleancache's providing of clean pagecache pages to transcendent memory. For optimal use of transcendent memory, both are necessary... because a kernel under memory pressure first reclaims clean pagecache pages and, when under more memory pressure, starts swapping anonymous pages. Frontswap and cleancache (which was merged at 3.0) are the "frontends" and the only necessary changes to the core kernel for transcendent memory; all other supporting code -- the "backends" -- is implemented as drivers. See the LWN.net article "Transcendent memory in a nutshell" for a detailed overview of frontswap and related kernel parts: https://lwn.net/Articles/454795/ Frontswap code was first posted publicly in January 2009 and on LKML in May 2009, and has remained functionally stable for nearly three years now. It is barely invasive, touching only the swap subsystem and adds less than 100 lines of code to existing swap subsystem code files. It has improved syntactically substantially between V1 and this posting of V14, thanks to the review of a few kernel developers, and has adapted easily to at least one major swap subsystem change. As of 3.4, there are three in-tree users of frontswap patiently waiting for this patchset and for CONFIG_FRONTSWAP to be enabled: zcache (staging driver merged at 2.6.39), Xen tmem (merged at 3.0 and 3.1) and RAMster (staging driver merged at 3.4). In addition, a RFC has been posted for a KVM backend. The frontswap patchset has been in linux-next since next-110603. Earlier versions of frontswap already ship in the Oracle Unbreakable Enterprise Kernel and SuSE SLES. This patch, 1of4, provides the header file for the core code for frontswap that interfaces between the hooks in the swap subsystem and a frontswap backend via frontswap_ops. --- New file added: include/linux/frontswap.h [v14: add support for writethrough, per suggestion by aarcange@redhat.com] [v14: rebase to 3.4-rc2] [v11: konrad.wilk@oracle.com: squashed s/flush/invalidate/ in] [v10: no change] [v9: akpm@linux-foundation.org: change "flush" to "invalidate", part 1] [v8: rebase to 3.0-rc4] [v7: rebase to 3.0-rc3] [v7: JBeulich@novell.com: new static inlines resolve to no-ops if not config'd] [v7: JBeulich@novell.com: avoid redundant shifts/divides for *_bit lib calls] [v6: rebase to 3.1-rc1] [v5: no change from v4] [v4: rebase to 2.6.39] Signed-off-by: Dan Magenheimer Reviewed-by: Andrew Morton Acked-by: Jan Beulich Acked-by: Seth Jennings Cc: Jeremy Fitzhardinge Cc: Hugh Dickins Cc: Johannes Weiner Cc: Nitin Gupta Cc: Matthew Wilcox Cc: Chris Mason Cc: Rik Riel [v15: int/bool on some functions] Signed-off-by: Konrad Wilk --- include/linux/frontswap.h | 127 ++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 127 insertions(+) create mode 100644 include/linux/frontswap.h (limited to 'include/linux') diff --git a/include/linux/frontswap.h b/include/linux/frontswap.h new file mode 100644 index 000000000000..68ff7af5c5fb --- /dev/null +++ b/include/linux/frontswap.h @@ -0,0 +1,127 @@ +#ifndef _LINUX_FRONTSWAP_H +#define _LINUX_FRONTSWAP_H + +#include +#include +#include + +struct frontswap_ops { + void (*init)(unsigned); + int (*put_page)(unsigned, pgoff_t, struct page *); + int (*get_page)(unsigned, pgoff_t, struct page *); + void (*invalidate_page)(unsigned, pgoff_t); + void (*invalidate_area)(unsigned); +}; + +extern bool frontswap_enabled; +extern struct frontswap_ops + frontswap_register_ops(struct frontswap_ops *ops); +extern void frontswap_shrink(unsigned long); +extern unsigned long frontswap_curr_pages(void); +extern void frontswap_writethrough(bool); + +extern void __frontswap_init(unsigned type); +extern int __frontswap_put_page(struct page *page); +extern int __frontswap_get_page(struct page *page); +extern void __frontswap_invalidate_page(unsigned, pgoff_t); +extern void __frontswap_invalidate_area(unsigned); + +#ifdef CONFIG_FRONTSWAP + +static inline bool frontswap_test(struct swap_info_struct *sis, pgoff_t offset) +{ + bool ret = false; + + if (frontswap_enabled && sis->frontswap_map) + ret = test_bit(offset, sis->frontswap_map); + return ret; +} + +static inline void frontswap_set(struct swap_info_struct *sis, pgoff_t offset) +{ + if (frontswap_enabled && sis->frontswap_map) + set_bit(offset, sis->frontswap_map); +} + +static inline void frontswap_clear(struct swap_info_struct *sis, pgoff_t offset) +{ + if (frontswap_enabled && sis->frontswap_map) + clear_bit(offset, sis->frontswap_map); +} + +static inline void frontswap_map_set(struct swap_info_struct *p, + unsigned long *map) +{ + p->frontswap_map = map; +} + +static inline unsigned long *frontswap_map_get(struct swap_info_struct *p) +{ + return p->frontswap_map; +} +#else +/* all inline routines become no-ops and all externs are ignored */ + +#define frontswap_enabled (0) + +static inline bool frontswap_test(struct swap_info_struct *sis, pgoff_t offset) +{ + return false; +} + +static inline void frontswap_set(struct swap_info_struct *sis, pgoff_t offset) +{ +} + +static inline void frontswap_clear(struct swap_info_struct *sis, pgoff_t offset) +{ +} + +static inline void frontswap_map_set(struct swap_info_struct *p, + unsigned long *map) +{ +} + +static inline unsigned long *frontswap_map_get(struct swap_info_struct *p) +{ + return NULL; +} +#endif + +static inline int frontswap_put_page(struct page *page) +{ + int ret = -1; + + if (frontswap_enabled) + ret = __frontswap_put_page(page); + return ret; +} + +static inline int frontswap_get_page(struct page *page) +{ + int ret = -1; + + if (frontswap_enabled) + ret = __frontswap_get_page(page); + return ret; +} + +static inline void frontswap_invalidate_page(unsigned type, pgoff_t offset) +{ + if (frontswap_enabled) + __frontswap_invalidate_page(type, offset); +} + +static inline void frontswap_invalidate_area(unsigned type) +{ + if (frontswap_enabled) + __frontswap_invalidate_area(type); +} + +static inline void frontswap_init(unsigned type) +{ + if (frontswap_enabled) + __frontswap_init(type); +} + +#endif /* _LINUX_FRONTSWAP_H */ -- cgit v1.2.3 From 38b5faf4b178d5279b1fca5d7dadc68881342660 Mon Sep 17 00:00:00 2001 From: Dan Magenheimer Date: Mon, 9 Apr 2012 17:08:06 -0600 Subject: mm: frontswap: core swap subsystem hooks and headers This patch, 2of4, contains the changes to the core swap subsystem. This includes: (1) makes available core swap data structures (swap_lock, swap_list and swap_info) that are needed by frontswap.c but we don't need to expose them to the dozens of files that include swap.h so we create a new swapfile.h just to extern-ify these and modify their declarations to non-static (2) adds frontswap-related elements to swap_info_struct. Frontswap_map points to vzalloc'ed one-bit-per-swap-page metadata that indicates whether the swap page is in frontswap or in the device and frontswap_pages counts how many pages are in frontswap. (3) adds hooks in the swap subsystem and extends try_to_unuse so that frontswap_shrink can do a "partial swapoff". Note that a failed frontswap_map allocation is safe... failure is noted by lack of "FS" in the subsequent printk. --- [v14: rebase to 3.4-rc2] [v10: no change] [v9: akpm@linux-foundation.org: mark some statics __read_mostly] [v9: akpm@linux-foundation.org: add clarifying comments] [v9: akpm@linux-foundation.org: no need to loop repeating try_to_unuse] [v9: error27@gmail.com: remove superfluous check for NULL] [v8: rebase to 3.0-rc4] [v8: kamezawa.hiroyu@jp.fujitsu.com: change counter to atomic_t to avoid races] [v8: kamezawa.hiroyu@jp.fujitsu.com: comment to clarify informational counters] [v7: rebase to 3.0-rc3] [v7: JBeulich@novell.com: add new swap struct elements only if config'd] [v6: rebase to 3.0-rc1] [v6: lliubbo@gmail.com: fix null pointer deref if vzalloc fails] [v6: konrad.wilk@oracl.com: various checks and code clarifications/comments] [v5: no change from v4] [v4: rebase to 2.6.39] Signed-off-by: Dan Magenheimer Reviewed-by: Kamezawa Hiroyuki Acked-by: Jan Beulich Acked-by: Seth Jennings Cc: Jeremy Fitzhardinge Cc: Hugh Dickins Cc: Johannes Weiner Cc: Nitin Gupta Cc: Matthew Wilcox Cc: Chris Mason Cc: Rik Riel Cc: Andrew Morton [v11: Rebased, fixed mm/swapfile.c context change] Signed-off-by: Konrad Rzeszutek Wilk --- include/linux/swap.h | 4 ++++ include/linux/swapfile.h | 13 +++++++++++++ 2 files changed, 17 insertions(+) create mode 100644 include/linux/swapfile.h (limited to 'include/linux') diff --git a/include/linux/swap.h b/include/linux/swap.h index b1fd5c7925fe..50a55e2d58ec 100644 --- a/include/linux/swap.h +++ b/include/linux/swap.h @@ -197,6 +197,10 @@ struct swap_info_struct { struct block_device *bdev; /* swap device or bdev of swap file */ struct file *swap_file; /* seldom referenced */ unsigned int old_block_size; /* seldom referenced */ +#ifdef CONFIG_FRONTSWAP + unsigned long *frontswap_map; /* frontswap in-use, one bit per page */ + atomic_t frontswap_pages; /* frontswap pages in-use counter */ +#endif }; struct swap_list_t { diff --git a/include/linux/swapfile.h b/include/linux/swapfile.h new file mode 100644 index 000000000000..e282624e8c10 --- /dev/null +++ b/include/linux/swapfile.h @@ -0,0 +1,13 @@ +#ifndef _LINUX_SWAPFILE_H +#define _LINUX_SWAPFILE_H + +/* + * these were static in swapfile.c but frontswap.c needs them and we don't + * want to expose them to the dozens of source files that include swap.h + */ +extern spinlock_t swap_lock; +extern struct swap_list_t swap_list; +extern struct swap_info_struct *swap_info[]; +extern int try_to_unuse(unsigned int, bool, unsigned long); + +#endif /* _LINUX_SWAPFILE_H */ -- cgit v1.2.3 From 165c8aed5bbc6bdddbccae0ba9db451732558ff9 Mon Sep 17 00:00:00 2001 From: Konrad Rzeszutek Wilk Date: Tue, 15 May 2012 11:32:15 -0400 Subject: frontswap: s/put_page/store/g s/get_page/load Sounds so much more natural. Suggested-by: Andrea Arcangeli Signed-off-by: Konrad Rzeszutek Wilk --- include/linux/frontswap.h | 16 ++++++++-------- 1 file changed, 8 insertions(+), 8 deletions(-) (limited to 'include/linux') diff --git a/include/linux/frontswap.h b/include/linux/frontswap.h index 68ff7af5c5fb..0e4e2eec5c1d 100644 --- a/include/linux/frontswap.h +++ b/include/linux/frontswap.h @@ -7,8 +7,8 @@ struct frontswap_ops { void (*init)(unsigned); - int (*put_page)(unsigned, pgoff_t, struct page *); - int (*get_page)(unsigned, pgoff_t, struct page *); + int (*store)(unsigned, pgoff_t, struct page *); + int (*load)(unsigned, pgoff_t, struct page *); void (*invalidate_page)(unsigned, pgoff_t); void (*invalidate_area)(unsigned); }; @@ -21,8 +21,8 @@ extern unsigned long frontswap_curr_pages(void); extern void frontswap_writethrough(bool); extern void __frontswap_init(unsigned type); -extern int __frontswap_put_page(struct page *page); -extern int __frontswap_get_page(struct page *page); +extern int __frontswap_store(struct page *page); +extern int __frontswap_load(struct page *page); extern void __frontswap_invalidate_page(unsigned, pgoff_t); extern void __frontswap_invalidate_area(unsigned); @@ -88,21 +88,21 @@ static inline unsigned long *frontswap_map_get(struct swap_info_struct *p) } #endif -static inline int frontswap_put_page(struct page *page) +static inline int frontswap_store(struct page *page) { int ret = -1; if (frontswap_enabled) - ret = __frontswap_put_page(page); + ret = __frontswap_store(page); return ret; } -static inline int frontswap_get_page(struct page *page) +static inline int frontswap_load(struct page *page) { int ret = -1; if (frontswap_enabled) - ret = __frontswap_get_page(page); + ret = __frontswap_load(page); return ret; } -- cgit v1.2.3