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@quantonium.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/linux/spinlock.h b/include/linux/spinlock.h
index a39186194cd6782ac0b6705f02af6179a86f7813..10fd28b118ee2353600e8d42bc7349a71948ecbb 100644 (file)
--- 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 d11c48ec8ffdbd32db32cf9258c8bb45e92e440b..a6c8529dd9b23ccff4d139b84bd0ac67369f25b0 100644 (file)
--- 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 (file)
index 0000000..266a97c
--- /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);