Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1423152Ab2JaPJr (ORCPT ); Wed, 31 Oct 2012 11:09:47 -0400 Received: from acsinet15.oracle.com ([141.146.126.227]:40124 "EHLO acsinet15.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1423087Ab2JaPJm (ORCPT ); Wed, 31 Oct 2012 11:09:42 -0400 From: Dan Magenheimer To: devel@linuxdriverproject.org, linux-kernel@vger.kernel.org, gregkh@linuxfoundation.org, linux-mm@kvack.org, ngupta@vflare.org, konrad.wilk@oracle.com, sjenning@linux.vnet.ibm.com, minchan@kernel.org, dan.magenheimer@oracle.com, fschmaus@gmail.com, andor.damm@googlemail.com, ilendir@googlemail.com, akpm@linux-foundation.org, mgorman@suse.de Subject: [PATCH 2/5] mm: frontswap: lazy initialization to allow tmem backends to build/run as modules Date: Wed, 31 Oct 2012 08:07:51 -0700 Message-Id: <1351696074-29362-3-git-send-email-dan.magenheimer@oracle.com> X-Mailer: git-send-email 1.7.5.1 In-Reply-To: <1351696074-29362-1-git-send-email-dan.magenheimer@oracle.com> References: <1351696074-29362-1-git-send-email-dan.magenheimer@oracle.com> X-Source-IP: ucsinet21.oracle.com [156.151.31.93] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5685 Lines: 180 With the goal of allowing tmem backends (zcache, ramster, Xen tmem) to be built/loaded as modules rather than built-in and enabled by a boot parameter, this patch provides "lazy initialization", allowing backends to register to frontswap even after swapon was run. Before a backend registers all calls to init are recorded and the creation of tmem_pools delayed until a backend registers or until a frontswap put is attempted. Signed-off-by: Stefan Hengelein Signed-off-by: Florian Schmaus Signed-off-by: Andor Daam Signed-off-by: Dan Magenheimer --- include/linux/frontswap.h | 1 + mm/frontswap.c | 70 +++++++++++++++++++++++++++++++++++++++----- 2 files changed, 63 insertions(+), 8 deletions(-) diff --git a/include/linux/frontswap.h b/include/linux/frontswap.h index 3044254..ef6ada6 100644 --- a/include/linux/frontswap.h +++ b/include/linux/frontswap.h @@ -23,6 +23,7 @@ extern void frontswap_writethrough(bool); extern void frontswap_tmem_exclusive_gets(bool); extern void __frontswap_init(unsigned type); +#define FRONTSWAP_HAS_LAZY_INIT extern int __frontswap_store(struct page *page); extern int __frontswap_load(struct page *page); extern void __frontswap_invalidate_page(unsigned, pgoff_t); diff --git a/mm/frontswap.c b/mm/frontswap.c index 2890e67..523a19b 100644 --- a/mm/frontswap.c +++ b/mm/frontswap.c @@ -80,6 +80,19 @@ static inline void inc_frontswap_succ_stores(void) { } static inline void inc_frontswap_failed_stores(void) { } static inline void inc_frontswap_invalidates(void) { } #endif + +/* + * When no backend is registered all calls to init are registered and + * remembered but fail to create tmem_pools. When a backend registers with + * frontswap the previous calls to init are executed to create tmem_pools + * and set the respective poolids. + * While no backend is registered all "puts", "gets" and "flushes" are + * ignored or fail. + */ +#define MAX_INITIALIZABLE_SD 32 +static int sds[MAX_INITIALIZABLE_SD]; +static int backend_registered; + /* * Register operations for frontswap, returning previous thus allowing * detection of multiple backends and possible nesting. @@ -87,9 +100,16 @@ static inline void inc_frontswap_invalidates(void) { } struct frontswap_ops frontswap_register_ops(struct frontswap_ops *ops) { struct frontswap_ops old = frontswap_ops; + int i; frontswap_ops = *ops; frontswap_enabled = true; + + backend_registered = 1; + for (i = 0; i < MAX_INITIALIZABLE_SD; i++) { + if (sds[i] != -1) + (*frontswap_ops.init)(sds[i]); + } return old; } EXPORT_SYMBOL(frontswap_register_ops); @@ -122,7 +142,10 @@ void __frontswap_init(unsigned type) BUG_ON(sis == NULL); if (sis->frontswap_map == NULL) return; - frontswap_ops.init(type); + if (backend_registered) { + (*frontswap_ops.init)(type); + sds[type] = type; + } } EXPORT_SYMBOL(__frontswap_init); @@ -147,10 +170,20 @@ int __frontswap_store(struct page *page) struct swap_info_struct *sis = swap_info[type]; pgoff_t offset = swp_offset(entry); + if (!backend_registered) { + inc_frontswap_failed_stores(); + return ret; + } + BUG_ON(!PageLocked(page)); BUG_ON(sis == NULL); if (frontswap_test(sis, offset)) dup = 1; + if (type < MAX_INITIALIZABLE_SD && sds[type] == -1) { + /* lazy init call to handle post-boot insmod backends*/ + (*frontswap_ops.init)(type); + sds[type] = type; + } ret = frontswap_ops.store(type, offset, page); if (ret == 0) { frontswap_set(sis, offset); @@ -186,6 +219,9 @@ int __frontswap_load(struct page *page) struct swap_info_struct *sis = swap_info[type]; pgoff_t offset = swp_offset(entry); + if (!backend_registered) + return ret; + BUG_ON(!PageLocked(page)); BUG_ON(sis == NULL); if (frontswap_test(sis, offset)) @@ -209,6 +245,9 @@ void __frontswap_invalidate_page(unsigned type, pgoff_t offset) { struct swap_info_struct *sis = swap_info[type]; + if (!backend_registered) + return; + BUG_ON(sis == NULL); if (frontswap_test(sis, offset)) { frontswap_ops.invalidate_page(type, offset); @@ -225,13 +264,23 @@ EXPORT_SYMBOL(__frontswap_invalidate_page); void __frontswap_invalidate_area(unsigned type) { struct swap_info_struct *sis = swap_info[type]; - - BUG_ON(sis == NULL); - if (sis->frontswap_map == NULL) - return; - frontswap_ops.invalidate_area(type); - atomic_set(&sis->frontswap_pages, 0); - memset(sis->frontswap_map, 0, sis->max / sizeof(long)); + int i; + + if (backend_registered) { + BUG_ON(sis == NULL); + if (sis->frontswap_map == NULL) + return; + (*frontswap_ops.invalidate_area)(type); + atomic_set(&sis->frontswap_pages, 0); + memset(sis->frontswap_map, 0, sis->max / sizeof(long)); + } else { + for (i = 0; i < MAX_INITIALIZABLE_SD; i++) { + if (sds[i] == type) { + sds[i] = -1; + break; + } + } + } } EXPORT_SYMBOL(__frontswap_invalidate_area); @@ -353,6 +402,7 @@ EXPORT_SYMBOL(frontswap_curr_pages); static int __init init_frontswap(void) { + int i; #ifdef CONFIG_DEBUG_FS struct dentry *root = debugfs_create_dir("frontswap", NULL); if (root == NULL) @@ -364,6 +414,10 @@ static int __init init_frontswap(void) debugfs_create_u64("invalidates", S_IRUGO, root, &frontswap_invalidates); #endif + for (i = 0; i < MAX_INITIALIZABLE_SD; i++) + sds[i] = -1; + + frontswap_enabled = 1; return 0; } -- 1.7.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/