[PATCH] mm: zsmalloc: Replace return type int with bool

[PATCH] mm: zsmalloc: Replace return type int with bool

[Souptick Joarder]

zs_register_migration() returns either 0 or 1.
So the return type int should be replaced with bool.

Signed-off-by: Souptick Joarder <jrdr.linux@gmail.com>
---
 mm/zsmalloc.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
index c301350..e238354 100644
--- a/mm/zsmalloc.c
+++ b/mm/zsmalloc.c
@@ -295,7 +295,7 @@ struct mapping_area {
 };

 #ifdef CONFIG_COMPACTION
-static int zs_register_migration(struct zs_pool *pool);
+static bool zs_register_migration(struct zs_pool *pool);
 static void zs_unregister_migration(struct zs_pool *pool);
 static void migrate_lock_init(struct zspage *zspage);
 static void migrate_read_lock(struct zspage *zspage);
@@ -306,7 +306,7 @@ struct mapping_area {
 #else
 static int zsmalloc_mount(void) { return 0; }
 static void zsmalloc_unmount(void) {}
-static int zs_register_migration(struct zs_pool *pool) { return 0; }
+static bool zs_register_migration(struct zs_pool *pool) { return 0; }
 static void zs_unregister_migration(struct zs_pool *pool) {}
 static void migrate_lock_init(struct zspage *zspage) {}
 static void migrate_read_lock(struct zspage *zspage) {}
@@ -2101,17 +2101,17 @@ void zs_page_putback(struct page *page)
 	.putback_page = zs_page_putback,
 };

-static int zs_register_migration(struct zs_pool *pool)
+static bool zs_register_migration(struct zs_pool *pool)
 {
 	pool->inode = alloc_anon_inode(zsmalloc_mnt->mnt_sb);
 	if (IS_ERR(pool->inode)) {
 		pool->inode = NULL;
-		return 1;
+		return true;
 	}

 	pool->inode->i_mapping->private_data = pool;
 	pool->inode->i_mapping->a_ops = &zsmalloc_aops;
-	return 0;
+	return false;
 }

 static void zs_unregister_migration(struct zs_pool *pool)
--
1.9.1

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Re: [PATCH] mm: zsmalloc: Replace return type int with bool

[Randy Dunlap]

On 02/19/18 11:42, Souptick Joarder wrote:
> zs_register_migration() returns either 0 or 1.
> So the return type int should be replaced with bool.
> 
> Signed-off-by: Souptick Joarder <jrdr.linux@gmail.com>
> ---
>  mm/zsmalloc.c | 10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
> index c301350..e238354 100644
> --- a/mm/zsmalloc.c
> +++ b/mm/zsmalloc.c
> @@ -295,7 +295,7 @@ struct mapping_area {
>  };
> 
>  #ifdef CONFIG_COMPACTION
> -static int zs_register_migration(struct zs_pool *pool);
> +static bool zs_register_migration(struct zs_pool *pool);
>  static void zs_unregister_migration(struct zs_pool *pool);
>  static void migrate_lock_init(struct zspage *zspage);
>  static void migrate_read_lock(struct zspage *zspage);
> @@ -306,7 +306,7 @@ struct mapping_area {
>  #else
>  static int zsmalloc_mount(void) { return 0; }
>  static void zsmalloc_unmount(void) {}
> -static int zs_register_migration(struct zs_pool *pool) { return 0; }
> +static bool zs_register_migration(struct zs_pool *pool) { return 0; }

                                                             return false;

>  static void zs_unregister_migration(struct zs_pool *pool) {}
>  static void migrate_lock_init(struct zspage *zspage) {}
>  static void migrate_read_lock(struct zspage *zspage) {}
> @@ -2101,17 +2101,17 @@ void zs_page_putback(struct page *page)
>  	.putback_page = zs_page_putback,
>  };
> 
> -static int zs_register_migration(struct zs_pool *pool)
> +static bool zs_register_migration(struct zs_pool *pool)
>  {
>  	pool->inode = alloc_anon_inode(zsmalloc_mnt->mnt_sb);
>  	if (IS_ERR(pool->inode)) {
>  		pool->inode = NULL;
> -		return 1;
> +		return true;
>  	}
> 
>  	pool->inode->i_mapping->private_data = pool;
>  	pool->inode->i_mapping->a_ops = &zsmalloc_aops;
> -	return 0;
> +	return false;
>  }
> 
>  static void zs_unregister_migration(struct zs_pool *pool)
> --

thanks,
-- 
~Randy

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Re: [PATCH] mm: zsmalloc: Replace return type int with bool

[kbuild test robot]

Hi Souptick,

Thank you for the patch! Perhaps something to improve:

[auto build test WARNING on mmotm/master]
[also build test WARNING on v4.16-rc2 next-20180219]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]

url:    https://github.com/0day-ci/linux/commits/Souptick-Joarder/mm-zsmalloc-Replace-return-type-int-with-bool/20180220-070147
base:   git://git.cmpxchg.org/linux-mmotm.git master


coccinelle warnings: (new ones prefixed by >>)

>> mm/zsmalloc.c:309:65-66: WARNING: return of 0/1 in function 'zs_register_migration' with return type bool

Please review and possibly fold the followup patch.

---
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[PATCH] mm: zsmalloc: fix boolreturn.cocci warnings

[kbuild test robot]

From: Fengguang Wu <fengguang.wu@intel.com>

mm/zsmalloc.c:309:65-66: WARNING: return of 0/1 in function 'zs_register_migration' with return type bool

 Return statements in functions returning bool should use
 true/false instead of 1/0.
Generated by: scripts/coccinelle/misc/boolreturn.cocci

Fixes: 3d58cbb028bb ("mm: zsmalloc: Replace return type int with bool")
CC: Souptick Joarder <jrdr.linux@gmail.com>
Signed-off-by: Fengguang Wu <fengguang.wu@intel.com>
---

 zsmalloc.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/mm/zsmalloc.c
+++ b/mm/zsmalloc.c
@@ -306,7 +306,7 @@ static void SetZsPageMovable(struct zs_p
 #else
 static int zsmalloc_mount(void) { return 0; }
 static void zsmalloc_unmount(void) {}
-static bool zs_register_migration(struct zs_pool *pool) { return 0; }
+static bool zs_register_migration(struct zs_pool *pool) { return false; }
 static void zs_unregister_migration(struct zs_pool *pool) {}
 static void migrate_lock_init(struct zspage *zspage) {}
 static void migrate_read_lock(struct zspage *zspage) {}

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Re: [PATCH] mm: zsmalloc: Replace return type int with bool

[Souptick Joarder]

On Tue, Feb 20, 2018 at 9:07 AM, kbuild test robot <lkp@intel.com> wrote:
> Hi Souptick,
>
> Thank you for the patch! Perhaps something to improve:
>
> [auto build test WARNING on mmotm/master]
> [also build test WARNING on v4.16-rc2 next-20180219]
> [if your patch is applied to the wrong git tree, please drop us a note to help improve the system]
>
> url:    https://github.com/0day-ci/linux/commits/Souptick-Joarder/mm-zsmalloc-Replace-return-type-int-with-bool/20180220-070147
> base:   git://git.cmpxchg.org/linux-mmotm.git master
>
>
> coccinelle warnings: (new ones prefixed by >>)
>
>>> mm/zsmalloc.c:309:65-66: WARNING: return of 0/1 in function 'zs_register_migration' with return type bool
>
> Please review and possibly fold the followup patch.
>

OK, I will send the v2.

> ---
> 0-DAY kernel test infrastructure                Open Source Technology Center
> https://lists.01.org/pipermail/kbuild-all                   Intel Corporation

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Re: [PATCH] mm: zsmalloc: Replace return type int with bool

[Minchan Kim]

Hi Souptick,

On Tue, Feb 20, 2018 at 01:09:26PM +0530, Souptick Joarder wrote:
> On Tue, Feb 20, 2018 at 9:07 AM, kbuild test robot <lkp@intel.com> wrote:
> > Hi Souptick,
> >
> > Thank you for the patch! Perhaps something to improve:
> >
> > [auto build test WARNING on mmotm/master]
> > [also build test WARNING on v4.16-rc2 next-20180219]
> > [if your patch is applied to the wrong git tree, please drop us a note to help improve the system]
> >
> > url:    https://github.com/0day-ci/linux/commits/Souptick-Joarder/mm-zsmalloc-Replace-return-type-int-with-bool/20180220-070147
> > base:   git://git.cmpxchg.org/linux-mmotm.git master
> >
> >
> > coccinelle warnings: (new ones prefixed by >>)
> >
> >>> mm/zsmalloc.c:309:65-66: WARNING: return of 0/1 in function 'zs_register_migration' with return type bool
> >
> > Please review and possibly fold the followup patch.
> >
> 
> OK, I will send the v2.

First of all, thanks for the patch.

Yub, bool could be more appropriate. However, there are lots of other places
in kernel where use int instead of bool.
If we fix every such places with each patch, it would be very painful.
If you believe it's really worth, it would be better to find/fix every
such places in one patch. But I'm not sure it's worth.

Thanks.

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Re: [PATCH] mm: zsmalloc: Replace return type int with bool

[Souptick Joarder]

On Tue, Feb 20, 2018 at 2:38 PM, Minchan Kim <minchan@kernel.org> wrote:
> Hi Souptick,
>
> On Tue, Feb 20, 2018 at 01:09:26PM +0530, Souptick Joarder wrote:
>> On Tue, Feb 20, 2018 at 9:07 AM, kbuild test robot <lkp@intel.com> wrote:
>> > Hi Souptick,
>> >
>> > Thank you for the patch! Perhaps something to improve:
>> >
>> > [auto build test WARNING on mmotm/master]
>> > [also build test WARNING on v4.16-rc2 next-20180219]
>> > [if your patch is applied to the wrong git tree, please drop us a note to help improve the system]
>> >
>> > url:    https://github.com/0day-ci/linux/commits/Souptick-Joarder/mm-zsmalloc-Replace-return-type-int-with-bool/20180220-070147
>> > base:   git://git.cmpxchg.org/linux-mmotm.git master
>> >
>> >
>> > coccinelle warnings: (new ones prefixed by >>)
>> >
>> >>> mm/zsmalloc.c:309:65-66: WARNING: return of 0/1 in function 'zs_register_migration' with return type bool
>> >
>> > Please review and possibly fold the followup patch.
>> >
>>
>> OK, I will send the v2.
>
> First of all, thanks for the patch.
>
> Yub, bool could be more appropriate. However, there are lots of other places
> in kernel where use int instead of bool.
> If we fix every such places with each patch, it would be very painful.
> If you believe it's really worth, it would be better to find/fix every
> such places in one patch. But I'm not sure it's worth.
>

Sure, I will create patch series and send it.

> Thanks.

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Re: [PATCH] mm: zsmalloc: Replace return type int with bool

[Matthew Wilcox]

On Tue, Feb 20, 2018 at 04:25:15PM +0530, Souptick Joarder wrote:
> On Tue, Feb 20, 2018 at 2:38 PM, Minchan Kim <minchan@kernel.org> wrote:
> > Yub, bool could be more appropriate. However, there are lots of other places
> > in kernel where use int instead of bool.
> > If we fix every such places with each patch, it would be very painful.
> > If you believe it's really worth, it would be better to find/fix every
> > such places in one patch. But I'm not sure it's worth.
> >
> 
> Sure, I will create patch series and send it.

Please don't.  If you're touching a function for another reason, it's
fine to convert it to return bool.  A series of patches converting every
function in the kernel that could be converted will not make friends.

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Re: [PATCH] mm: zsmalloc: Replace return type int with bool

[Matthew Wilcox]

On Tue, Feb 20, 2018 at 04:52:46AM -0800, Matthew Wilcox wrote:
> On Tue, Feb 20, 2018 at 04:25:15PM +0530, Souptick Joarder wrote:
> > On Tue, Feb 20, 2018 at 2:38 PM, Minchan Kim <minchan@kernel.org> wrote:
> > > Yub, bool could be more appropriate. However, there are lots of other places
> > > in kernel where use int instead of bool.
> > > If we fix every such places with each patch, it would be very painful.
> > > If you believe it's really worth, it would be better to find/fix every
> > > such places in one patch. But I'm not sure it's worth.
> > >
> > 
> > Sure, I will create patch series and send it.
> 
> Please don't.  If you're touching a function for another reason, it's
> fine to convert it to return bool.  A series of patches converting every
> function in the kernel that could be converted will not make friends.

... but if you're looking for something to do, here's something from my
TODO list that's in the same category.

The vm_ops fault, huge_fault, page_mkwrite and pfn_mkwrite handlers are
currently defined to return an int (see linux/mm.h).  Unlike the majority
of functions which return int, these functions are supposed to return
one or more of the VM_FAULT flags.  There's general agreement that this
should become a new typedef, vm_fault_t.  We can do a gradual conversion;
start off by adding

typedef int vm_fault_t;

to linux/mm.h.  Then the individual drivers can be converted (one patch
per driver) to return vm_fault_t from those handlers (probably about
180 patches, so take it slowly).  Once all drivers are converted, we
can change that typedef to:

typedef enum {
	VM_FAULT_OOM	= 1,
	VM_FAULT_SIGBUS	= 2,
	VM_FAULT_MAJOR	= 4,
...
} vm_fault_t;

and then the compiler will warn if anyone tries to introduce a new handler
that returns int.

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Re: [PATCH] mm: zsmalloc: Replace return type int with bool

[Souptick Joarder]

Hi Matthew,

On Tue, Feb 20, 2018 at 7:07 PM, Matthew Wilcox <willy@infradead.org> wrote:
> On Tue, Feb 20, 2018 at 04:52:46AM -0800, Matthew Wilcox wrote:
>> On Tue, Feb 20, 2018 at 04:25:15PM +0530, Souptick Joarder wrote:
>> > On Tue, Feb 20, 2018 at 2:38 PM, Minchan Kim <minchan@kernel.org> wrote:
>> > > Yub, bool could be more appropriate. However, there are lots of other places
>> > > in kernel where use int instead of bool.
>> > > If we fix every such places with each patch, it would be very painful.
>> > > If you believe it's really worth, it would be better to find/fix every
>> > > such places in one patch. But I'm not sure it's worth.
>> > >
>> >
>> > Sure, I will create patch series and send it.
>>
>> Please don't.  If you're touching a function for another reason, it's
>> fine to convert it to return bool.  A series of patches converting every
>> function in the kernel that could be converted will not make friends.
>
> ... but if you're looking for something to do, here's something from my
> TODO list that's in the same category.

Thanks. I would like to take it.
>
> The vm_ops fault, huge_fault, page_mkwrite and pfn_mkwrite handlers are
> currently defined to return an int (see linux/mm.h).  Unlike the majority
> of functions which return int, these functions are supposed to return
> one or more of the VM_FAULT flags.  There's general agreement that this
> should become a new typedef, vm_fault_t.  We can do a gradual conversion;
> start off by adding
>
> typedef int vm_fault_t;
>
> to linux/mm.h.  Then the individual drivers can be converted (one patch
> per driver) to return vm_fault_t from those handlers (probably about
> 180 patches, so take it slowly).  Once all drivers are converted, we
> can change that typedef to:
>
> typedef enum {
>         VM_FAULT_OOM    = 1,
>         VM_FAULT_SIGBUS = 2,
>         VM_FAULT_MAJOR  = 4,
> ...
> } vm_fault_t;
>
> and then the compiler will warn if anyone tries to introduce a new handler
> that returns int.
>

Let me go through the shared details and will reply you back
before making any changes.

-Souptick

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