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Message-ID: <20121031134246.GF27288@phenom.dumpdata.com>
Date: Wed, 31 Oct 2012 09:42:46 -0400
From: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
To: Cesar Eduardo Barros <cesarb@...arb.net>
Cc: Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
linux-kernel@...r.kernel.org,
Dan Magenheimer <dan.magenheimer@...cle.com>,
Mel Gorman <mgorman@...e.de>, Rik van Riel <riel@...hat.com>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
Johannes Weiner <hannes@...xchg.org>
Subject: Re: [PATCH RFC] mm: simplify frontswap_init()
On Tue, Oct 30, 2012 at 09:12:53PM -0200, Cesar Eduardo Barros wrote:
> The function frontswap_init() uses the passed parameter only to check
> for the presence of the frontswap_map. It is also passed down to
> frontswap_ops.init(), but all implementations of it in the kernel ignore
> the parameter.
>
> Do the check for frontswap_map in the caller instead and remove the
> parameter from frontswap_init() and frontswap_ops.init().
>
> Also, __frontswap_init() was exported, but its only caller (via an
> inline function) is mm/swapfile.c, which cannot be built as a module.
> Remove the unnecessary export.
>
> Signed-off-by: Cesar Eduardo Barros <cesarb@...arb.net>
> ---
>
> Not even compile tested, just a quick patch to show what I was thinking
> of, but feel free to apply if you think it is good.
That looks good.
>
> I might write another patch to move it outside the lock later, but I
> would have to read the frontswap code more carefully first.
>
> drivers/staging/ramster/zcache-main.c | 2 +-
> drivers/staging/zcache/zcache-main.c | 2 +-
> drivers/xen/tmem.c | 2 +-
> include/linux/frontswap.h | 8 ++++----
> mm/frontswap.c | 10 ++--------
> mm/swapfile.c | 3 ++-
> 6 files changed, 11 insertions(+), 16 deletions(-)
>
> diff --git a/drivers/staging/ramster/zcache-main.c b/drivers/staging/ramster/zcache-main.c
> index a09dd5c..b3f01c9 100644
> --- a/drivers/staging/ramster/zcache-main.c
> +++ b/drivers/staging/ramster/zcache-main.c
> @@ -1610,7 +1610,7 @@ static void zcache_frontswap_flush_area(unsigned type)
> }
> }
>
> -static void zcache_frontswap_init(unsigned ignored)
> +static void zcache_frontswap_init(void)
> {
> /* a single tmem poolid is used for all frontswap "types" (swapfiles) */
> if (zcache_frontswap_poolid < 0)
> diff --git a/drivers/staging/zcache/zcache-main.c b/drivers/staging/zcache/zcache-main.c
> index 52b43b7..cb67635 100644
> --- a/drivers/staging/zcache/zcache-main.c
> +++ b/drivers/staging/zcache/zcache-main.c
> @@ -1903,7 +1903,7 @@ static void zcache_frontswap_flush_area(unsigned type)
> }
> }
>
> -static void zcache_frontswap_init(unsigned ignored)
> +static void zcache_frontswap_init(void)
> {
> /* a single tmem poolid is used for all frontswap "types" (swapfiles) */
> if (zcache_frontswap_poolid < 0)
> diff --git a/drivers/xen/tmem.c b/drivers/xen/tmem.c
> index 144564e..7156ff0 100644
> --- a/drivers/xen/tmem.c
> +++ b/drivers/xen/tmem.c
> @@ -343,7 +343,7 @@ static void tmem_frontswap_flush_area(unsigned type)
> (void)xen_tmem_flush_object(pool, oswiz(type, ind));
> }
>
> -static void tmem_frontswap_init(unsigned ignored)
> +static void tmem_frontswap_init(void)
> {
> struct tmem_pool_uuid private = TMEM_POOL_PRIVATE_UUID;
>
> diff --git a/include/linux/frontswap.h b/include/linux/frontswap.h
> index 3044254..6374c80 100644
> --- a/include/linux/frontswap.h
> +++ b/include/linux/frontswap.h
> @@ -6,7 +6,7 @@
> #include <linux/bitops.h>
>
> struct frontswap_ops {
> - void (*init)(unsigned);
> + void (*init)(void);
> int (*store)(unsigned, pgoff_t, struct page *);
> int (*load)(unsigned, pgoff_t, struct page *);
> void (*invalidate_page)(unsigned, pgoff_t);
> @@ -22,7 +22,7 @@ extern void frontswap_writethrough(bool);
> #define FRONTSWAP_HAS_EXCLUSIVE_GETS
> extern void frontswap_tmem_exclusive_gets(bool);
>
> -extern void __frontswap_init(unsigned type);
> +extern void __frontswap_init(void);
> extern int __frontswap_store(struct page *page);
> extern int __frontswap_load(struct page *page);
> extern void __frontswap_invalidate_page(unsigned, pgoff_t);
> @@ -120,10 +120,10 @@ static inline void frontswap_invalidate_area(unsigned type)
> __frontswap_invalidate_area(type);
> }
>
> -static inline void frontswap_init(unsigned type)
> +static inline void frontswap_init(void)
> {
> if (frontswap_enabled)
> - __frontswap_init(type);
> + __frontswap_init();
> }
>
> #endif /* _LINUX_FRONTSWAP_H */
> diff --git a/mm/frontswap.c b/mm/frontswap.c
> index 2890e67..d13661b 100644
> --- a/mm/frontswap.c
> +++ b/mm/frontswap.c
> @@ -115,16 +115,10 @@ EXPORT_SYMBOL(frontswap_tmem_exclusive_gets);
> /*
> * Called when a swap device is swapon'd.
> */
> -void __frontswap_init(unsigned type)
> +void __frontswap_init(void)
> {
> - struct swap_info_struct *sis = swap_info[type];
> -
> - BUG_ON(sis == NULL);
> - if (sis->frontswap_map == NULL)
> - return;
> - frontswap_ops.init(type);
> + frontswap_ops.init();
> }
> -EXPORT_SYMBOL(__frontswap_init);
>
> static inline void __frontswap_clear(struct swap_info_struct *sis, pgoff_t offset)
> {
> diff --git a/mm/swapfile.c b/mm/swapfile.c
> index 088daf4..28c26bd 100644
> --- a/mm/swapfile.c
> +++ b/mm/swapfile.c
> @@ -1479,7 +1479,8 @@ static void enable_swap_info(struct swap_info_struct *p, int prio,
> {
> spin_lock(&swap_lock);
> _enable_swap_info(p, prio, swap_map, frontswap_map);
> - frontswap_init(p->type);
> + if (frontswap_map)
> + frontswap_init();
> spin_unlock(&swap_lock);
> }
>
> --
> 1.7.11.7
--
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