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, for example,
"rcu_nocbs=all:1/2" would offload all the even-numbered CPUs regardless
of the number of CPUs on the system.

Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Yury Norov <yury.norov@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

diff --git a/Documentation/admin-guide/kernel-parameters.rst b/Documentation/admin-guide/kernel-parameters.rst
index 3996b54..01ba293 100644 (file)
--- 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,
+so that "nohz_full=all" is the equivalent of "nohz_full=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 74ceb02..6e29b2a 100644 (file)
--- 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 9cd5755..4ea73f5 100644 (file)
--- 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},