linux-kernel - [PATCH 1/3] lib: add "all" and "none" as valid ranges to bitmap

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Date:   Thu, 21 Jan 2021 17:33:53 -0500
From:   Paul Gortmaker <paul.gortmaker@...driver.com>
To:     linux-kernel@...r.kernel.org
Cc:     Paul Gortmaker <paul.gortmaker@...driver.com>,
        Yury Norov <yury.norov@...il.com>,
        Peter Zijlstra <peterz@...radead.org>,
        "Paul E. McKenney" <paulmck@...nel.org>
Subject: [PATCH 1/3] lib: add "all" and "none" as valid ranges to bitmap_parselist()

The use of "all" was originally RCU specific - I'd pushed it down to
being used for any CPU lists -- then Yuri suggested pushing it down
further to be used by any bitmap, which is done here.

As a trivial one line extension, we also accept the inverse "none"
as a valid alias.

Cc: Yury Norov <yury.norov@...il.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: "Paul E. McKenney" <paulmck@...nel.org>
Signed-off-by: Paul Gortmaker <paul.gortmaker@...driver.com>
---
 Documentation/admin-guide/kernel-parameters.rst | 11 +++++++++++
 lib/bitmap.c                                    |  9 +++++++++
 2 files changed, 20 insertions(+)

diff --git a/Documentation/admin-guide/kernel-parameters.rst b/Documentation/admin-guide/kernel-parameters.rst
index 682ab28b5c94..5e080080b058 100644
--- a/Documentation/admin-guide/kernel-parameters.rst
+++ b/Documentation/admin-guide/kernel-parameters.rst
@@ -68,7 +68,18 @@ For example one can add to the command line following parameter:
 
 where the final item represents CPUs 100,101,125,126,150,151,...
 
+The following convenience aliases are also accepted and used:
 
+        foo_cpus=all
+
+will provide an full/all-set cpu mask for the associated boot argument.
+
+        foo_cpus=none
+
+will provide an empty/cleared cpu mask for the associated boot argument.
+
+Note that "all" and "none" are not necessarily valid/sensible input values
+for each available boot parameter expecting a CPU list.
 
 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 75006c4036e9..a1010646fbe5 100644
--- a/lib/bitmap.c
+++ b/lib/bitmap.c
@@ -627,6 +627,7 @@ static const char *bitmap_parse_region(const char *str, struct region *r)
  * From each group will be used only defined amount of bits.
  * Syntax: range:used_size/group_size
  * Example: 0-1023:2/256 ==> 0,1,256,257,512,513,768,769
+ * Optionally the self-descriptive "all" or "none" can be used.
  *
  * Returns: 0 on success, -errno on invalid input strings. Error values:
  *
@@ -640,8 +641,16 @@ int bitmap_parselist(const char *buf, unsigned long *maskp, int nmaskbits)
 	struct region r;
 	long ret;
 
+	if (!strcmp(buf, "all")) {
+		bitmap_fill(maskp, nmaskbits);
+		return 0;
+	}
+
 	bitmap_zero(maskp, nmaskbits);
 
+	if (!strcmp(buf, "none"))
+		return 0;
+
 	while (buf) {
 		buf = bitmap_find_region(buf);
 		if (buf == NULL)
-- 
2.17.1