netdev - [PATCH net-next 4/5] spinlock: Add library function to allocate spinlock buckets array

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Date:   Thu, 30 Nov 2017 16:03:04 -0800
From:   Tom Herbert <tom@...ntonium.net>
To:     davem@...emloft.net
Cc:     netdev@...r.kernel.org, rohit@...ntonium.net,
        herbert@...dor.apana.org.au, Tom Herbert <tom@...ntonium.net>
Subject: [PATCH net-next 4/5] spinlock: Add library function to allocate spinlock buckets array

Add two new library functions: alloc_bucket_spinlocks and
free_bucket_spinlocks. These are used to allocate and free an array
of spinlocks that are useful as locks for hash buckets. The interface
specifies the maximum number of spinlocks in the array as well
as a CPU multiplier to derive the number of spinlocks to allocate.
The number allocated is rounded up to a power of two to make the
array amenable to hash lookup.

Signed-off-by: Tom Herbert <tom@...ntonium.net>
---
 include/linux/spinlock.h |  6 ++++++
 lib/Makefile             |  2 +-
 lib/bucket_locks.c       | 54 ++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 61 insertions(+), 1 deletion(-)
 create mode 100644 lib/bucket_locks.c

diff --git a/include/linux/spinlock.h b/include/linux/spinlock.h
index a39186194cd6..10fd28b118ee 100644
--- a/include/linux/spinlock.h
+++ b/include/linux/spinlock.h
@@ -414,4 +414,10 @@ extern int _atomic_dec_and_lock(atomic_t *atomic, spinlock_t *lock);
 #define atomic_dec_and_lock(atomic, lock) \
 		__cond_lock(lock, _atomic_dec_and_lock(atomic, lock))
 
+int alloc_bucket_spinlocks(spinlock_t **locks, unsigned int *lock_mask,
+			   size_t max_size, unsigned int cpu_mult,
+			   gfp_t gfp);
+
+void free_bucket_spinlocks(spinlock_t *locks);
+
 #endif /* __LINUX_SPINLOCK_H */
diff --git a/lib/Makefile b/lib/Makefile
index d11c48ec8ffd..a6c8529dd9b2 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -39,7 +39,7 @@ obj-y += bcd.o div64.o sort.o parser.o debug_locks.o random32.o \
 	 gcd.o lcm.o list_sort.o uuid.o flex_array.o iov_iter.o clz_ctz.o \
 	 bsearch.o find_bit.o llist.o memweight.o kfifo.o \
 	 percpu-refcount.o percpu_ida.o rhashtable.o reciprocal_div.o \
-	 once.o refcount.o usercopy.o errseq.o
+	 once.o refcount.o usercopy.o errseq.o bucket_locks.o
 obj-$(CONFIG_STRING_SELFTEST) += test_string.o
 obj-y += string_helpers.o
 obj-$(CONFIG_TEST_STRING_HELPERS) += test-string_helpers.o
diff --git a/lib/bucket_locks.c b/lib/bucket_locks.c
new file mode 100644
index 000000000000..266a97c5708b
--- /dev/null
+++ b/lib/bucket_locks.c
@@ -0,0 +1,54 @@
+#include <linux/export.h>
+#include <linux/kernel.h>
+#include <linux/mm.h>
+#include <linux/slab.h>
+#include <linux/vmalloc.h>
+
+/* Allocate an array of spinlocks to be accessed by a hash. Two arguments
+ * indicate the number of elements to allocate in the array. max_size
+ * gives the maximum number of elements to allocate. cpu_mult gives
+ * the number of locks per CPU to allocate. The size is rounded up
+ * to a power of 2 to be suitable as a hash table.
+ */
+
+int alloc_bucket_spinlocks(spinlock_t **locks, unsigned int *locks_mask,
+			   size_t max_size, unsigned int cpu_mult, gfp_t gfp)
+{
+	spinlock_t *tlocks = NULL;
+	unsigned int i, size;
+#if defined(CONFIG_PROVE_LOCKING)
+	unsigned int nr_pcpus = 2;
+#else
+	unsigned int nr_pcpus = num_possible_cpus();
+#endif
+
+	if (cpu_mult) {
+		nr_pcpus = min_t(unsigned int, nr_pcpus, 64UL);
+		size = min_t(unsigned int, nr_pcpus * cpu_mult, max_size);
+	} else {
+		size = max_size;
+	}
+
+	if (sizeof(spinlock_t) != 0) {
+		if (gfpflags_allow_blocking(gfp))
+			tlocks = kvmalloc(size * sizeof(spinlock_t), gfp);
+		else
+			tlocks = kmalloc_array(size, sizeof(spinlock_t), gfp);
+		if (!tlocks)
+			return -ENOMEM;
+		for (i = 0; i < size; i++)
+			spin_lock_init(&tlocks[i]);
+	}
+
+	*locks = tlocks;
+	*locks_mask = size - 1;
+
+	return 0;
+}
+EXPORT_SYMBOL(alloc_bucket_spinlocks);
+
+void free_bucket_spinlocks(spinlock_t *locks)
+{
+	kvfree(locks);
+}
+EXPORT_SYMBOL(free_bucket_spinlocks);
-- 
2.11.0