[PATCH 0/2] bitmap_parselist: support 'all' semantics

[PATCH 0/2] bitmap_parselist: support 'all' semantics

[Yury Norov]

RCU code supports a special group 'all' which selects all bits in a bitmap.
We have recently added 'N' extension for bitmap parse, so that '0-N' would
have exactly the same meaning as 'all'. But because the 'all' is already
used by RCU, it would be reasonable to support it in core bitmap code as a
common and easy-readable alias for '0-N'.

Moving the 'all' support to core bitmap code adds another level of
flexibility for system configuration by supporting patterns. For example,
every second bit in cpumask may be selected like this:
	isolcpus=all:1/2


Yury Norov (2):
  bitmap_parse: support 'all' semantics
  rcu/tree_plugin: don't handle the case of 'all' CPU range

 Documentation/admin-guide/kernel-parameters.rst | 5 +++++
 kernel/rcu/tree_plugin.h                        | 9 +++------
 lib/bitmap.c                                    | 9 +++++++++
 lib/test_bitmap.c                               | 8 +++++++-
 4 files changed, 24 insertions(+), 7 deletions(-)

-- 
2.25.1

[PATCH 1/2] bitmap_parse: support 'all' semantics

[Yury Norov]

RCU code supports an 'all' group as a special case when parsing
rcu_nocbs parameter. This patch moves the 'all' support to the core
bitmap_parse code, so that all bitmap users can enjoy this extension.

Moving 'all' parsing to a bitmap_parse level, also allows users to
pass patterns together with 'all' in regular group:pattern format

Signed-off-by: Yury Norov <yury.norov@gmail.com>
---
 Documentation/admin-guide/kernel-parameters.rst | 5 +++++
 lib/bitmap.c                                    | 9 +++++++++
 lib/test_bitmap.c                               | 8 +++++++-
 3 files changed, 21 insertions(+), 1 deletion(-)

diff --git a/Documentation/admin-guide/kernel-parameters.rst b/Documentation/admin-guide/kernel-parameters.rst
index 3996b54158bf..7178d9c4de7f 100644
--- a/Documentation/admin-guide/kernel-parameters.rst
+++ b/Documentation/admin-guide/kernel-parameters.rst
@@ -76,6 +76,11 @@ to change, such as less cores in the CPU list, then N and any ranges using N
 will also change.  Use the same on a small 4 core system, and "16-N" becomes
 "16-3" and now the same boot input will be flagged as invalid (start > end).
 
+The special case-tolerant group name "all" has a meaning of selecting all CPUs,
+such that "isolcpus=all" is the equivalent of "isolcpus=0-N".
+
+The semantics of "N" and "all" is supported on a level of bitmaps and holds for
+all users of bitmap_parse().
 
 This document may not be entirely up to date and comprehensive. The command
 "modinfo -p ${modulename}" shows a current list of all parameters of a loadable
diff --git a/lib/bitmap.c b/lib/bitmap.c
index 74ceb02f45e3..6e29b2aae6ba 100644
--- a/lib/bitmap.c
+++ b/lib/bitmap.c
@@ -581,6 +581,14 @@ static const char *bitmap_parse_region(const char *str, struct region *r)
 {
 	unsigned int lastbit = r->nbits - 1;
 
+	if (!strncasecmp(str, "all", 3)) {
+		r->start = 0;
+		r->end = lastbit;
+		str += 3;
+
+		goto check_pattern;
+	}
+
 	str = bitmap_getnum(str, &r->start, lastbit);
 	if (IS_ERR(str))
 		return str;
@@ -595,6 +603,7 @@ static const char *bitmap_parse_region(const char *str, struct region *r)
 	if (IS_ERR(str))
 		return str;
 
+check_pattern:
 	if (end_of_region(*str))
 		goto no_pattern;
 
diff --git a/lib/test_bitmap.c b/lib/test_bitmap.c
index 9cd575583180..ab278cfa9145 100644
--- a/lib/test_bitmap.c
+++ b/lib/test_bitmap.c
@@ -366,6 +366,13 @@ static const struct test_bitmap_parselist parselist_tests[] __initconst = {
 	{0, "0-31:1/3,1-31:1/3,2-31:1/3",	&exp1[8 * step], 32, 0},
 	{0, "1-10:8/12,8-31:24/29,0-31:0/3",	&exp1[9 * step], 32, 0},
 
+	{0,	  "all",		&exp1[8 * step], 32, 0},
+	{0,	  "0, 1, all,  ",	&exp1[8 * step], 32, 0},
+	{0,	  "all:1/2",		&exp1[4 * step], 32, 0},
+	{0,	  "ALL:1/2",		&exp1[4 * step], 32, 0},
+	{-EINVAL, "al", NULL, 8, 0},
+	{-EINVAL, "alll", NULL, 8, 0},
+
 	{-EINVAL, "-1",	NULL, 8, 0},
 	{-EINVAL, "-0",	NULL, 8, 0},
 	{-EINVAL, "10-1", NULL, 8, 0},
@@ -384,7 +391,6 @@ static const struct test_bitmap_parselist parselist_tests[] __initconst = {
 	{-EINVAL, "a-31:10/1", NULL, 8, 0},
 	{-EINVAL, "0-31:a/1", NULL, 8, 0},
 	{-EINVAL, "0-\n", NULL, 8, 0},
-
 };
 
 static void __init test_bitmap_parselist(void)
-- 
2.25.1

[PATCH 2/2] rcu/tree_plugin: don't handle the case of 'all' CPU range

[Yury Norov]

The 'all' semantics is now supported by the bitmap_parselist() so we can
drop supporting it as a special case in RCU code. This patch does not
add any functional changes for existing users.

Signed-off-by: Yury Norov <yury.norov@gmail.com>
---
 kernel/rcu/tree_plugin.h | 9 +++------
 1 file changed, 3 insertions(+), 6 deletions(-)

diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index 464b16132866..334eaf4d561f 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -1511,13 +1511,10 @@ static void rcu_cleanup_after_idle(void)
 static int __init rcu_nocb_setup(char *str)
 {
 	alloc_bootmem_cpumask_var(&rcu_nocb_mask);
-	if (!strcasecmp(str, "all"))		/* legacy: use "0-N" instead */
+	if (cpulist_parse(str, rcu_nocb_mask)) {
+		pr_warn("rcu_nocbs= bad CPU range, all CPUs set\n");
 		cpumask_setall(rcu_nocb_mask);
-	else
-		if (cpulist_parse(str, rcu_nocb_mask)) {
-			pr_warn("rcu_nocbs= bad CPU range, all CPUs set\n");
-			cpumask_setall(rcu_nocb_mask);
-		}
+	}
 	return 1;
 }
 __setup("rcu_nocbs=", rcu_nocb_setup);
-- 
2.25.1

Re: [PATCH 1/2] bitmap_parse: support 'all' semantics

[Andy Shevchenko]

On Mon, Apr 19, 2021 at 05:01:30PM -0700, Yury Norov wrote:
> RCU code supports an 'all' group as a special case when parsing
> rcu_nocbs parameter. This patch moves the 'all' support to the core
> bitmap_parse code, so that all bitmap users can enjoy this extension.
> 
> Moving 'all' parsing to a bitmap_parse level, also allows users to
> pass patterns together with 'all' in regular group:pattern format

...

>  	{0, "0-31:1/3,1-31:1/3,2-31:1/3",	&exp1[8 * step], 32, 0},
>  	{0, "1-10:8/12,8-31:24/29,0-31:0/3",	&exp1[9 * step], 32, 0},
>  
> +	{0,	  "all",		&exp1[8 * step], 32, 0},
> +	{0,	  "0, 1, all,  ",	&exp1[8 * step], 32, 0},
> +	{0,	  "all:1/2",		&exp1[4 * step], 32, 0},
> +	{0,	  "ALL:1/2",		&exp1[4 * step], 32, 0},

> +	{-EINVAL, "al", NULL, 8, 0},
> +	{-EINVAL, "alll", NULL, 8, 0},
> +

Looking at the below hunk it seems like the two above should be actually placed
there.

>  	{-EINVAL, "-1",	NULL, 8, 0},
>  	{-EINVAL, "-0",	NULL, 8, 0},
>  	{-EINVAL, "10-1", NULL, 8, 0},
> @@ -384,7 +391,6 @@ static const struct test_bitmap_parselist parselist_tests[] __initconst = {
>  	{-EINVAL, "a-31:10/1", NULL, 8, 0},
>  	{-EINVAL, "0-31:a/1", NULL, 8, 0},
>  	{-EINVAL, "0-\n", NULL, 8, 0},
> -

Otherwise this change doesn't belong to the series.

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH 2/2] rcu/tree_plugin: don't handle the case of 'all' CPU range

[Andy Shevchenko]

On Mon, Apr 19, 2021 at 05:01:31PM -0700, Yury Norov wrote:
> The 'all' semantics is now supported by the bitmap_parselist() so we can
> drop supporting it as a special case in RCU code. This patch does not
> add any functional changes for existing users.

> -	if (!strcasecmp(str, "all"))		/* legacy: use "0-N" instead */

Perhaps move comment as well to new location.

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH 0/2] bitmap_parselist: support 'all' semantics

[Andy Shevchenko]

On Mon, Apr 19, 2021 at 05:01:29PM -0700, Yury Norov wrote:
> RCU code supports a special group 'all' which selects all bits in a bitmap.
> We have recently added 'N' extension for bitmap parse, so that '0-N' would
> have exactly the same meaning as 'all'. But because the 'all' is already
> used by RCU, it would be reasonable to support it in core bitmap code as a
> common and easy-readable alias for '0-N'.
> 
> Moving the 'all' support to core bitmap code adds another level of
> flexibility for system configuration by supporting patterns. For example,
> every second bit in cpumask may be selected like this:
> 	isolcpus=all:1/2

After addressing a couple of nit-picks,
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

> Yury Norov (2):
>   bitmap_parse: support 'all' semantics
>   rcu/tree_plugin: don't handle the case of 'all' CPU range
> 
>  Documentation/admin-guide/kernel-parameters.rst | 5 +++++
>  kernel/rcu/tree_plugin.h                        | 9 +++------
>  lib/bitmap.c                                    | 9 +++++++++
>  lib/test_bitmap.c                               | 8 +++++++-
>  4 files changed, 24 insertions(+), 7 deletions(-)
> 
> -- 
> 2.25.1
> 

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH 1/2] bitmap_parse: support 'all' semantics

[Yury Norov]

On Tue, Apr 20, 2021 at 01:17:52PM +0300, Andy Shevchenko wrote:
> On Mon, Apr 19, 2021 at 05:01:30PM -0700, Yury Norov wrote:
> > RCU code supports an 'all' group as a special case when parsing
> > rcu_nocbs parameter. This patch moves the 'all' support to the core
> > bitmap_parse code, so that all bitmap users can enjoy this extension.
> > 
> > Moving 'all' parsing to a bitmap_parse level, also allows users to
> > pass patterns together with 'all' in regular group:pattern format
> 
> ...
> 
> >  	{0, "0-31:1/3,1-31:1/3,2-31:1/3",	&exp1[8 * step], 32, 0},
> >  	{0, "1-10:8/12,8-31:24/29,0-31:0/3",	&exp1[9 * step], 32, 0},
> >  
> > +	{0,	  "all",		&exp1[8 * step], 32, 0},
> > +	{0,	  "0, 1, all,  ",	&exp1[8 * step], 32, 0},
> > +	{0,	  "all:1/2",		&exp1[4 * step], 32, 0},
> > +	{0,	  "ALL:1/2",		&exp1[4 * step], 32, 0},
> 
> > +	{-EINVAL, "al", NULL, 8, 0},
> > +	{-EINVAL, "alll", NULL, 8, 0},
> > +
> 
> Looking at the below hunk it seems like the two above should be actually placed
> there.
> 
> >  	{-EINVAL, "-1",	NULL, 8, 0},
> >  	{-EINVAL, "-0",	NULL, 8, 0},
> >  	{-EINVAL, "10-1", NULL, 8, 0},
> > @@ -384,7 +391,6 @@ static const struct test_bitmap_parselist parselist_tests[] __initconst = {
> >  	{-EINVAL, "a-31:10/1", NULL, 8, 0},
> >  	{-EINVAL, "0-31:a/1", NULL, 8, 0},
> >  	{-EINVAL, "0-\n", NULL, 8, 0},
> > -
> 
> Otherwise this change doesn't belong to the series.

My bad, I'll fix it in v2.

Re: [PATCH 2/2] rcu/tree_plugin: don't handle the case of 'all' CPU range

[Yury Norov]

On Tue, Apr 20, 2021 at 01:18:40PM +0300, Andy Shevchenko wrote:
> On Mon, Apr 19, 2021 at 05:01:31PM -0700, Yury Norov wrote:
> > The 'all' semantics is now supported by the bitmap_parselist() so we can
> > drop supporting it as a special case in RCU code. This patch does not
> > add any functional changes for existing users.
> 
> > -	if (!strcasecmp(str, "all"))		/* legacy: use "0-N" instead */
> 
> Perhaps move comment as well to new location.

I actually wanted to remove this comment. The reason is that 'all' is
verbose, clear and proven to be useful for at least RCU. In v2 I'll
mention it explicitly in commit comment.

[PATCH 2/2] rcu/tree_plugin: don't handle the case of 'all' CPU range

[Yury Norov]

The 'all' semantics is now supported by the bitmap_parselist() so we can
drop supporting it as a special case in RCU code. Since 'all' is properly
supported in core bitmap code, drop legacy comment in RCU for it.

This patch does not add any functional changes for existing users.

Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Yury Norov <yury.norov@gmail.com>
---
 kernel/rcu/tree_plugin.h | 9 +++------
 1 file changed, 3 insertions(+), 6 deletions(-)

diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index 464b16132866..334eaf4d561f 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -1511,13 +1511,10 @@ static void rcu_cleanup_after_idle(void)
 static int __init rcu_nocb_setup(char *str)
 {
 	alloc_bootmem_cpumask_var(&rcu_nocb_mask);
-	if (!strcasecmp(str, "all"))		/* legacy: use "0-N" instead */
+	if (cpulist_parse(str, rcu_nocb_mask)) {
+		pr_warn("rcu_nocbs= bad CPU range, all CPUs set\n");
 		cpumask_setall(rcu_nocb_mask);
-	else
-		if (cpulist_parse(str, rcu_nocb_mask)) {
-			pr_warn("rcu_nocbs= bad CPU range, all CPUs set\n");
-			cpumask_setall(rcu_nocb_mask);
-		}
+	}
 	return 1;
 }
 __setup("rcu_nocbs=", rcu_nocb_setup);
-- 
2.25.1