On Wed, Oct 31, 2012 at 12:05:32PM -0500, Seth Jennings wrote: > On 10/31/2012 10:07 AM, Dan Magenheimer wrote: > > 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 <ilen...@googlemail.com> > > Signed-off-by: Florian Schmaus <fschm...@gmail.com> > > Signed-off-by: Andor Daam <andor.d...@googlemail.com> > > Signed-off-by: Dan Magenheimer <dan.magenhei...@oracle.com> > > --- > > 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 > > MAX_INITIALIZABLE_SD should just be MAX_SWAPFILES > > > +static int sds[MAX_INITIALIZABLE_SD]; > > Rather than store and array of enabled types indexed by type, why not > an array of booleans indexed by type. Or a bitfield if you really > want to save space. > > > +static int backend_registered; > > (backend_registered) is equivalent to checking (frontswap_ops != NULL) > right? > > > + > > /* > > * 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; > > This is weird, storing the type in an array indexed by type. Hence my > suggestion above about an array of booleans or a bitfield. > > > + } > > } > > 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) { > > Additional weirdness with sds. It seems this whole for loop could > just be reduced to: > > sds[type] = -1;
How does this look? (I hadn't actually tested it, but did compile test it) >From f545530e9ef2b0623ab9e78d490595e3b7eaa3fa Mon Sep 17 00:00:00 2001 From: Dan Magenheimer <dan.magenhei...@oracle.com> Date: Wed, 31 Oct 2012 08:07:51 -0700 Subject: [PATCH 2/2] mm: frontswap: lazy initialization to allow tmem backends to build/run as modules 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 <ilen...@googlemail.com> Signed-off-by: Florian Schmaus <fschm...@gmail.com> Signed-off-by: Andor Daam <andor.d...@googlemail.com> Signed-off-by: Dan Magenheimer <dan.magenhei...@oracle.com> [v1: Fixes per Seth Jennings suggestions] Signed-off-by: Konrad Rzeszutek Wilk <konrad.w...@oracle.com> --- include/linux/frontswap.h | 1 + mm/frontswap.c | 59 +++++++++++++++++++++++++++++++++++++++++------ 2 files changed, 53 insertions(+), 7 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..4e04549 100644 --- a/mm/frontswap.c +++ b/mm/frontswap.c @@ -80,6 +80,18 @@ 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. + */ +static DECLARE_BITMAP(sds, MAX_SWAPFILES); +static bool backend_registered __read_mostly; + /* * Register operations for frontswap, returning previous thus allowing * detection of multiple backends and possible nesting. @@ -87,9 +99,16 @@ 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 = true; + for (i = 0; i < MAX_SWAPFILES; i++) { + if (test_bit(i, sds)) + (*frontswap_ops.init)(sds[i]); + } return old; } EXPORT_SYMBOL(frontswap_register_ops); @@ -122,7 +141,10 @@ 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); + set_bit(type, sds); + } } EXPORT_SYMBOL(__frontswap_init); @@ -147,10 +169,20 @@ 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_SWAPFILES && !test_bit(type, sds)) { + /* lazy init call to handle post-boot insmod backends*/ + (*frontswap_ops.init)(type); + set_bit(type, sds); + } ret = frontswap_ops.store(type, offset, page); if (ret == 0) { frontswap_set(sis, offset); @@ -186,6 +218,9 @@ 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 +244,9 @@ 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); @@ -226,12 +264,16 @@ 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)); + 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 { + bitmap_zero(sds, MAX_SWAPFILES); + } } EXPORT_SYMBOL(__frontswap_invalidate_area); @@ -364,6 +406,9 @@ static int __init init_frontswap(void) debugfs_create_u64("invalidates", S_IRUGO, root, &frontswap_invalidates); #endif + bitmap_zero(sds, MAX_SWAPFILES); + + frontswap_enabled = 1; return 0; } -- 1.7.11.7 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/