From 1e01c968db3d0aebd48e31db15f24516b03128df Mon Sep 17 00:00:00 2001 From: Konrad Rzeszutek Wilk Date: Tue, 30 Apr 2013 15:26:51 -0700 Subject: [PATCH] frontswap: make frontswap_init use a pointer for the ops This simplifies the code in the frontswap - we can get rid of the 'backend_registered' test and instead check against frontswap_ops. [v1: Rebase on top of 703ba7fe5e0 (ramster->zcache move] Signed-off-by: Konrad Rzeszutek Wilk Signed-off-by: Bob Liu Cc: Wanpeng Li Cc: Andor Daam Cc: Dan Magenheimer Cc: Florian Schmaus Cc: Minchan Kim Cc: Stefan Hengelein Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- drivers/staging/zcache/zcache-main.c | 8 +++--- drivers/xen/tmem.c | 6 ++--- include/linux/frontswap.h | 2 +- mm/frontswap.c | 38 +++++++++++++--------------- 4 files changed, 26 insertions(+), 28 deletions(-) diff --git a/drivers/staging/zcache/zcache-main.c b/drivers/staging/zcache/zcache-main.c index e23d814b5392..09c69c8026f9 100644 --- a/drivers/staging/zcache/zcache-main.c +++ b/drivers/staging/zcache/zcache-main.c @@ -1707,9 +1707,9 @@ static struct frontswap_ops zcache_frontswap_ops = { .init = zcache_frontswap_init }; -struct frontswap_ops zcache_frontswap_register_ops(void) +struct frontswap_ops *zcache_frontswap_register_ops(void) { - struct frontswap_ops old_ops = + struct frontswap_ops *old_ops = frontswap_register_ops(&zcache_frontswap_ops); return old_ops; @@ -1874,7 +1874,7 @@ static int __init zcache_init(void) pr_warn("%s: cleancache_ops overridden\n", namestr); } if (zcache_enabled && !disable_frontswap) { - struct frontswap_ops old_ops; + struct frontswap_ops *old_ops; old_ops = zcache_frontswap_register_ops(); if (frontswap_has_exclusive_gets) @@ -1886,7 +1886,7 @@ static int __init zcache_init(void) namestr, frontswap_has_exclusive_gets, !disable_frontswap_ignore_nonactive); #endif - if (old_ops.init != NULL) + if (old_ops != NULL) pr_warn("%s: frontswap_ops overridden\n", namestr); } if (ramster_enabled) diff --git a/drivers/xen/tmem.c b/drivers/xen/tmem.c index 3ee836d42581..7a01a5fd0f63 100644 --- a/drivers/xen/tmem.c +++ b/drivers/xen/tmem.c @@ -362,7 +362,7 @@ static int __init no_frontswap(char *s) } __setup("nofrontswap", no_frontswap); -static struct frontswap_ops __initdata tmem_frontswap_ops = { +static struct frontswap_ops tmem_frontswap_ops = { .store = tmem_frontswap_store, .load = tmem_frontswap_load, .invalidate_page = tmem_frontswap_flush_page, @@ -378,11 +378,11 @@ static int __init xen_tmem_init(void) #ifdef CONFIG_FRONTSWAP if (tmem_enabled && use_frontswap) { char *s = ""; - struct frontswap_ops old_ops = + struct frontswap_ops *old_ops = frontswap_register_ops(&tmem_frontswap_ops); tmem_frontswap_poolid = -1; - if (old_ops.init != NULL) + if (old_ops) s = " (WARNING: frontswap_ops overridden)"; printk(KERN_INFO "frontswap enabled, RAM provided by " "Xen Transcendent Memory%s\n", s); diff --git a/include/linux/frontswap.h b/include/linux/frontswap.h index 30442547b9e6..d4f29875c7cc 100644 --- a/include/linux/frontswap.h +++ b/include/linux/frontswap.h @@ -14,7 +14,7 @@ struct frontswap_ops { }; extern bool frontswap_enabled; -extern struct frontswap_ops +extern struct frontswap_ops * frontswap_register_ops(struct frontswap_ops *ops); extern void frontswap_shrink(unsigned long); extern unsigned long frontswap_curr_pages(void); diff --git a/mm/frontswap.c b/mm/frontswap.c index cbd2b8af8129..e44c9cbd1443 100644 --- a/mm/frontswap.c +++ b/mm/frontswap.c @@ -24,7 +24,7 @@ * frontswap_ops is set by frontswap_register_ops to contain the pointers * to the frontswap "backend" implementation functions. */ -static struct frontswap_ops frontswap_ops __read_mostly; +static struct frontswap_ops *frontswap_ops __read_mostly; /* * This global enablement flag reduces overhead on systems where frontswap_ops @@ -108,41 +108,39 @@ static inline void inc_frontswap_invalidates(void) { } * * The time between the backend being registered and the swap file system * calling the backend (via the frontswap_* functions) is indeterminate as - * backend_registered is not atomic_t (or a value guarded by a spinlock). + * 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 - * ignorning or failing the requests - at which point backend_registered + * ignorning or failing the requests - at which point frontswap_ops * would have to be made in some fashion atomic. */ static DECLARE_BITMAP(need_init, MAX_SWAPFILES); -static bool backend_registered __read_mostly; /* * Register operations for frontswap, returning previous thus allowing * detection of multiple backends and possible nesting. */ -struct frontswap_ops frontswap_register_ops(struct frontswap_ops *ops) +struct frontswap_ops *frontswap_register_ops(struct frontswap_ops *ops) { - struct frontswap_ops old = frontswap_ops; + struct frontswap_ops *old = frontswap_ops; int i; - frontswap_ops = *ops; frontswap_enabled = true; for (i = 0; i < MAX_SWAPFILES; i++) { if (test_and_clear_bit(i, need_init)) - (*frontswap_ops.init)(i); + ops->init(i); } /* - * We MUST have backend_registered set _after_ the frontswap_init's + * We MUST have frontswap_ops set _after_ the frontswap_init's * have been called. Otherwise __frontswap_store might fail. Hence * the barrier to make sure compiler does not re-order us. */ barrier(); - backend_registered = true; + frontswap_ops = ops; return old; } EXPORT_SYMBOL(frontswap_register_ops); @@ -172,11 +170,11 @@ void __frontswap_init(unsigned type) { struct swap_info_struct *sis = swap_info[type]; - if (backend_registered) { + if (frontswap_ops) { BUG_ON(sis == NULL); if (sis->frontswap_map == NULL) return; - (*frontswap_ops.init)(type); + frontswap_ops->init(type); } else { BUG_ON(type > MAX_SWAPFILES); set_bit(type, need_init); @@ -206,7 +204,7 @@ int __frontswap_store(struct page *page) struct swap_info_struct *sis = swap_info[type]; pgoff_t offset = swp_offset(entry); - if (!backend_registered) { + if (!frontswap_ops) { inc_frontswap_failed_stores(); return ret; } @@ -215,7 +213,7 @@ int __frontswap_store(struct page *page) BUG_ON(sis == NULL); if (frontswap_test(sis, offset)) dup = 1; - ret = frontswap_ops.store(type, offset, page); + ret = frontswap_ops->store(type, offset, page); if (ret == 0) { frontswap_set(sis, offset); inc_frontswap_succ_stores(); @@ -250,13 +248,13 @@ int __frontswap_load(struct page *page) struct swap_info_struct *sis = swap_info[type]; pgoff_t offset = swp_offset(entry); - if (!backend_registered) + if (!frontswap_ops) return ret; BUG_ON(!PageLocked(page)); BUG_ON(sis == NULL); if (frontswap_test(sis, offset)) - ret = frontswap_ops.load(type, offset, page); + ret = frontswap_ops->load(type, offset, page); if (ret == 0) { inc_frontswap_loads(); if (frontswap_tmem_exclusive_gets_enabled) { @@ -276,12 +274,12 @@ void __frontswap_invalidate_page(unsigned type, pgoff_t offset) { struct swap_info_struct *sis = swap_info[type]; - if (!backend_registered) + if (!frontswap_ops) return; BUG_ON(sis == NULL); if (frontswap_test(sis, offset)) { - frontswap_ops.invalidate_page(type, offset); + frontswap_ops->invalidate_page(type, offset); __frontswap_clear(sis, offset); inc_frontswap_invalidates(); } @@ -296,11 +294,11 @@ void __frontswap_invalidate_area(unsigned type) { struct swap_info_struct *sis = swap_info[type]; - if (backend_registered) { + if (frontswap_ops) { BUG_ON(sis == NULL); if (sis->frontswap_map == NULL) return; - (*frontswap_ops.invalidate_area)(type); + frontswap_ops->invalidate_area(type); atomic_set(&sis->frontswap_pages, 0); memset(sis->frontswap_map, 0, sis->max / sizeof(long)); } -- 2.20.1