[PATCH 1/3] sbitmap: ensure that sbitmap maps are properly aligned

[Jens Axboe <axboe@kernel.dk>]

We try to be careful with alignment for cache purposes, but all of
that is worthless if we don't actually align the maps themselves.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
---
 include/linux/sbitmap.h | 11 ++++++++---
 lib/sbitmap.c           |  7 +++++--
 2 files changed, 13 insertions(+), 5 deletions(-)

diff --git a/include/linux/sbitmap.h b/include/linux/sbitmap.h
index 804a50983ec5..5cb1755d32da 100644
--- a/include/linux/sbitmap.h
+++ b/include/linux/sbitmap.h
@@ -63,9 +63,14 @@ struct sbitmap {
 	unsigned int map_nr;
 
 	/**
-	 * @map: Allocated bitmap.
+	 * @map: Aligned allocated bitmap.
 	 */
 	struct sbitmap_word *map;
+
+	/**
+	 * @map_ptr: Originally allocated map pointer
+	 */
+	void *map_ptr;
 };
 
 #define SBQ_WAIT_QUEUES 8
@@ -157,8 +162,8 @@ int sbitmap_init_node(struct sbitmap *sb, unsigned int depth, int shift,
  */
 static inline void sbitmap_free(struct sbitmap *sb)
 {
-	kfree(sb->map);
-	sb->map = NULL;
+	kfree(sb->map_ptr);
+	sb->map_ptr = sb->map = NULL;
 }
 
 /**
diff --git a/lib/sbitmap.c b/lib/sbitmap.c
index 45cab6bbc1c7..21e776e3128d 100644
--- a/lib/sbitmap.c
+++ b/lib/sbitmap.c
@@ -25,6 +25,7 @@ int sbitmap_init_node(struct sbitmap *sb, unsigned int depth, int shift,
 {
 	unsigned int bits_per_word;
 	unsigned int i;
+	size_t size;
 
 	if (shift < 0) {
 		shift = ilog2(BITS_PER_LONG);
@@ -52,9 +53,11 @@ int sbitmap_init_node(struct sbitmap *sb, unsigned int depth, int shift,
 		return 0;
 	}
 
-	sb->map = kcalloc_node(sb->map_nr, sizeof(*sb->map), flags, node);
-	if (!sb->map)
+	size = sb->map_nr * sizeof(*sb->map) + L1_CACHE_BYTES - 1;
+	sb->map_ptr = kzalloc_node(size, flags, node);
+	if (!sb->map_ptr)
 		return -ENOMEM;
+	sb->map = PTR_ALIGN(sb->map_ptr, L1_CACHE_BYTES);
 
 	for (i = 0; i < sb->map_nr; i++) {
 		sb->map[i].depth = min(depth, bits_per_word);
-- 
2.17.1