percpu: make pcpu_block_md generic

In reality, a chunk is just a block covering a larger number of bits.
The hints themselves are one in the same. Rather than maintaining the
hints separately, first introduce nr_bits to genericize
pcpu_block_update() to correctly maintain block->right_free. The next
patch will convert chunk hints to be managed as a pcpu_block_md.
Signed-off-by: Dennis Zhou <dennis@kernel.org>
Reviewed-by: Peng Fan <peng.fan@nxp.com>

mm/percpu-internal.h

@@ -28,6 +28,7 @@ struct pcpu_block_md {
 	int                     right_free;     /* size of free space along
 						   the right side of the block */
 	int                     first_free;     /* block position of first free */
+	int			nr_bits;	/* total bits responsible for */
 };
 
 struct pcpu_chunk {

mm/percpu.c

@@ -654,7 +654,7 @@ static void pcpu_block_update(struct pcpu_block_md *block, int start, int end)
 	if (start == 0)
 		block->left_free = contig;
 
-	if (end == PCPU_BITMAP_BLOCK_BITS)
+	if (end == block->nr_bits)
 		block->right_free = contig;
 
 	if (contig > block->contig_hint) {
@@ -1267,18 +1267,24 @@ static void pcpu_free_area(struct pcpu_chunk *chunk, int off)
 	pcpu_chunk_relocate(chunk, oslot);
 }
 
+static void pcpu_init_md_block(struct pcpu_block_md *block, int nr_bits)
+{
+	block->scan_hint = 0;
+	block->contig_hint = nr_bits;
+	block->left_free = nr_bits;
+	block->right_free = nr_bits;
+	block->first_free = 0;
+	block->nr_bits = nr_bits;
+}
+
 static void pcpu_init_md_blocks(struct pcpu_chunk *chunk)
 {
 	struct pcpu_block_md *md_block;
 
 	for (md_block = chunk->md_blocks;
 	     md_block != chunk->md_blocks + pcpu_chunk_nr_blocks(chunk);
-	     md_block++) {
-		md_block->scan_hint = 0;
-		md_block->contig_hint = PCPU_BITMAP_BLOCK_BITS;
-		md_block->left_free = PCPU_BITMAP_BLOCK_BITS;
-		md_block->right_free = PCPU_BITMAP_BLOCK_BITS;
-	}
+	     md_block++)
+		pcpu_init_md_block(md_block, PCPU_BITMAP_BLOCK_BITS);
 }
 
 /**