linux-kernel - [PATCH 1/4] cpumask: un-inline cpulist_parse for SMP; prepare for ascii helpers

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Date:   Mon,  9 Nov 2020 23:07:22 -0500
From:   Paul Gortmaker <paul.gortmaker@...driver.com>
To:     linux-kernel@...r.kernel.org
Cc:     cgroups@...r.kernel.org, rdunlap@...radead.org,
        colin.king@...onical.com,
        Paul Gortmaker <paul.gortmaker@...driver.com>
Subject: [PATCH 1/4] cpumask: un-inline cpulist_parse for SMP; prepare for ascii helpers

In order to support convenience tokens like "all", and "none" and
"last" in CPU lists, we'll have to use string operations and expand
on what is currently a simple wrapper around the underlying bitmap
function call.

Rather than add header dependencies to cpumask.h and code more complex
operations not really appropriate for a header file, we prepare by
simply un-inlining it here and move it to the lib dir alongside the
other more complex cpumask functions.

Since lib/cpumask.c is built conditionally on CONFIG_SMP, and there
are non-SMP callers, we leave the one-line stub behind for that case.
If they want to check "0-0" is a valid range, they can still do it.
In the meantime, we can add the ascii helpers for CONFIG_SMP users.
The use of NR_CPUS vs. CONFIG_SMP is consistent with the existing file.

Aside from an additional exported symbol in the SMP case, no functional
changes are anticipated with this move.

Signed-off-by: Paul Gortmaker <paul.gortmaker@...driver.com>
---
 include/linux/cpumask.h |  8 ++++++++
 lib/cpumask.c           | 13 +++++++++++++
 2 files changed, 21 insertions(+)

diff --git a/include/linux/cpumask.h b/include/linux/cpumask.h
index f0d895d6ac39..d2e370c5ce99 100644
--- a/include/linux/cpumask.h
+++ b/include/linux/cpumask.h
@@ -679,11 +679,19 @@ static inline int cpumask_parse(const char *buf, struct cpumask *dstp)
  * @dstp: the cpumask to set.
  *
  * Returns -errno, or 0 for success.
+ *
+ * There are instances of non-SMP callers of this, and the easiest way
+ * to remain 100% runtime compatible is to let them continue to have the
+ * one-line stub, while the SMP version in lib/cpumask.c gets improved.
  */
+#if NR_CPUS == 1
 static inline int cpulist_parse(const char *buf, struct cpumask *dstp)
 {
 	return bitmap_parselist(buf, cpumask_bits(dstp), nr_cpumask_bits);
 }
+#else
+int cpulist_parse(const char *buf, struct cpumask *dstp);
+#endif
 
 /**
  * cpumask_size - size to allocate for a 'struct cpumask' in bytes
diff --git a/lib/cpumask.c b/lib/cpumask.c
index 85da6ab4fbb5..5eb002237404 100644
--- a/lib/cpumask.c
+++ b/lib/cpumask.c
@@ -95,6 +95,19 @@ int cpumask_next_wrap(int n, const struct cpumask *mask, int start, bool wrap)
 }
 EXPORT_SYMBOL(cpumask_next_wrap);
 
+/**
+ * cpulist_parse - extract a cpumask from a user string of ranges
+ * @buf: the buffer to extract from
+ * @dstp: the cpumask to set.
+ *
+ * Returns -errno, or 0 for success.
+ */
+int cpulist_parse(const char *buf, struct cpumask *dstp)
+{
+	return bitmap_parselist(buf, cpumask_bits(dstp), nr_cpumask_bits);
+}
+EXPORT_SYMBOL(cpulist_parse);
+
 /* These are not inline because of header tangles. */
 #ifdef CONFIG_CPUMASK_OFFSTACK
 /**
-- 
2.25.1