zram: refactor writeback helpers

Move writeback-related functions and data structures from zram_drv.[ch]
to a new zram_wb.[ch] file. This is a pure refactoring patch with no
functional changes, preparing the ground for the upcoming asynchronous
writeback implementation.

Signed-off-by: Richard Chang <[email protected]>

Author: Richard Chang

drivers/block/zram/Makefile

@@ -8,5 +8,6 @@ zram-$(CONFIG_ZRAM_BACKEND_LZ4HC)	+= backend_lz4hc.o
 zram-$(CONFIG_ZRAM_BACKEND_ZSTD)	+= backend_zstd.o
 zram-$(CONFIG_ZRAM_BACKEND_DEFLATE)	+= backend_deflate.o
 zram-$(CONFIG_ZRAM_BACKEND_842)		+= backend_842.o
+zram-$(CONFIG_ZRAM_WRITEBACK)		+= zram_wb.o
 
 obj-$(CONFIG_ZRAM)	+=	zram.o

drivers/block/zram/zram_drv.c

@@ -36,6 +36,7 @@
 #include <linux/kernel_read_file.h>
 
 #include "zram_drv.h"
+#include "zram_wb.h"
 
 static DEFINE_IDR(zram_index_idr);
 /* idr index must be protected */
@@ -233,22 +234,6 @@ static void zram_accessed(struct zram *zram, u32 index)
 }
 
 #if defined CONFIG_ZRAM_WRITEBACK || defined CONFIG_ZRAM_MULTI_COMP
-struct zram_pp_slot {
-	unsigned long		index;
-	struct list_head	entry;
-};
-
-/*
- * A post-processing bucket is, essentially, a size class, this defines
- * the range (in bytes) of pp-slots sizes in particular bucket.
- */
-#define PP_BUCKET_SIZE_RANGE	64
-#define NUM_PP_BUCKETS		((PAGE_SIZE / PP_BUCKET_SIZE_RANGE) + 1)
-
-struct zram_pp_ctl {
-	struct list_head	pp_buckets[NUM_PP_BUCKETS];
-};
-
 static struct zram_pp_ctl *init_pp_ctl(void)
 {
 	struct zram_pp_ctl *ctl;
@@ -697,31 +682,6 @@ static ssize_t backing_dev_store(struct device *dev,
 	return err;
 }
 
-static unsigned long alloc_block_bdev(struct zram *zram)
-{
-	unsigned long blk_idx = 1;
-retry:
-	/* skip 0 bit to confuse zram.handle = 0 */
-	blk_idx = find_next_zero_bit(zram->bitmap, zram->nr_pages, blk_idx);
-	if (blk_idx == zram->nr_pages)
-		return 0;
-
-	if (test_and_set_bit(blk_idx, zram->bitmap))
-		goto retry;
-
-	atomic64_inc(&zram->stats.bd_count);
-	return blk_idx;
-}
-
-static void free_block_bdev(struct zram *zram, unsigned long blk_idx)
-{
-	int was_set;
-
-	was_set = test_and_clear_bit(blk_idx, zram->bitmap);
-	WARN_ON_ONCE(!was_set);
-	atomic64_dec(&zram->stats.bd_count);
-}
-
 static void read_from_bdev_async(struct zram *zram, struct page *page,
 			unsigned long entry, struct bio *parent)
 {
@@ -1111,8 +1071,6 @@ static int read_from_bdev(struct zram *zram, struct page *page,
 {
 	return -EIO;
 }
-
-static void free_block_bdev(struct zram *zram, unsigned long blk_idx) {};
 #endif
 
 #ifdef CONFIG_ZRAM_MEMORY_TRACKING

drivers/block/zram/zram_drv.h

@@ -139,4 +139,23 @@ struct zram {
 #endif
 	atomic_t pp_in_progress;
 };
+
+#if defined CONFIG_ZRAM_WRITEBACK || defined CONFIG_ZRAM_MULTI_COMP
+struct zram_pp_slot {
+	unsigned long		index;
+	struct list_head	entry;
+};
+
+/*
+ * A post-processing bucket is, essentially, a size class, this defines
+ * the range (in bytes) of pp-slots sizes in particular bucket.
+ */
+#define PP_BUCKET_SIZE_RANGE	64
+#define NUM_PP_BUCKETS		((PAGE_SIZE / PP_BUCKET_SIZE_RANGE) + 1)
+
+struct zram_pp_ctl {
+	struct list_head	pp_buckets[NUM_PP_BUCKETS];
+};
+#endif
+
 #endif

drivers/block/zram/zram_wb.c

@@ -0,0 +1,35 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#define KMSG_COMPONENT "zram_wb"
+#define pr_fmt(fmt) KMSG_COMPONENT ": " fmt
+
+#include <linux/module.h>
+#include <linux/kernel.h>
+
+#include "zram_wb.h"
+
+unsigned long alloc_block_bdev(struct zram *zram)
+{
+	unsigned long blk_idx = 1;
+retry:
+	/* skip 0 bit to confuse zram.handle = 0 */
+	blk_idx = find_next_zero_bit(zram->bitmap, zram->nr_pages, blk_idx);
+	if (blk_idx == zram->nr_pages)
+		return 0;
+
+	if (test_and_set_bit(blk_idx, zram->bitmap))
+		goto retry;
+
+	atomic64_inc(&zram->stats.bd_count);
+	return blk_idx;
+}
+
+void free_block_bdev(struct zram *zram, unsigned long blk_idx)
+{
+	int was_set;
+
+	was_set = test_and_clear_bit(blk_idx, zram->bitmap);
+	WARN_ON_ONCE(!was_set);
+	atomic64_dec(&zram->stats.bd_count);
+}
+

drivers/block/zram/zram_wb.h

@@ -0,0 +1,18 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
+#ifndef _ZRAM_WRITEBACK_H_
+#define _ZRAM_WRITEBACK_H_
+
+#include <linux/bio.h>
+#include "zram_drv.h"
+
+#if IS_ENABLED(CONFIG_ZRAM_WRITEBACK)
+unsigned long alloc_block_bdev(struct zram *zram);
+void free_block_bdev(struct zram *zram, unsigned long blk_idx);
+#else
+inline unsigned long alloc_block_bdev(struct zram *zram) { return 0; }
+inline void free_block_bdev(struct zram *zram, unsigned long blk_idx) {};
+#endif
+
+#endif /* _ZRAM_WRITEBACK_H_ */
+