Merge branch 'rhashtable-New-features-in-walk-and-bucket'

Tom Herbert says:

====================
rhashtable: New features in walk and bucket

This patch contains some changes to related rhashtable:

- Above allow rhashtable_walk_start to return void
- Add a functon to peek at the next entry during a walk
- Abstract out function to compute a has for a table
- A library function to alloc a spinlocks bucket array
- Call the above function for rhashtable locks allocation

Tested: Exercised using various operations on an ILA xlat
table.

v2:
 - Apply feedback from Herbert. Don't change semantics of resize
   event reporting and -EAGAIN, just simplify API for callers that
   ignore those.
 - Add end_of_table in iter to reliably tell when the iterator has
   reached to the eno.
====================

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

1 files changed, 54 insertions, 0 deletions

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);