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

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Message-Id: <20210420000131.21038-2-yury.norov@gmail.com>
Date:   Mon, 19 Apr 2021 17:01:30 -0700
From:   Yury Norov <yury.norov@...il.com>
To:     linux-kernel@...r.kernel.org, rcu@...r.kernel.org,
        linux-doc@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        "Paul E. McKenney" <paulmck@...nel.org>
Cc:     Yury Norov <yury.norov@...il.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Joel Fernandes <joel@...lfernandes.org>,
        Jonathan Corbet <corbet@....net>,
        Lai Jiangshan <jiangshanlai@...il.com>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Palmer Dabbelt <palmerdabbelt@...gle.com>,
        Paul Gortmaker <paul.gortmaker@...driver.com>,
        Randy Dunlap <rdunlap@...radead.org>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        Steven Rostedt <rostedt@...dmis.org>
Subject: [PATCH 1/2] bitmap_parse: support 'all' semantics

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@...il.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