zram: refactor flags and writeback stuff

Rename some variables and restructure some code for better readability in
writeback and zs_free_page.

Link: http://lkml.kernel.org/r/20181127055429.251614-4-minchan@kernel.orgSigned-off-by: Minchan Kim <minchan@kernel.org>
Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Reviewed-by: Joey Pabalinas <joeypabalinas@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/block/zram/zram_drv.c

@@ -55,17 +55,17 @@ static void zram_free_page(struct zram *zram, size_t index);
 
 static int zram_slot_trylock(struct zram *zram, u32 index)
 {
-	return bit_spin_trylock(ZRAM_LOCK, &zram->table[index].value);
+	return bit_spin_trylock(ZRAM_LOCK, &zram->table[index].flags);
 }
 
 static void zram_slot_lock(struct zram *zram, u32 index)
 {
-	bit_spin_lock(ZRAM_LOCK, &zram->table[index].value);
+	bit_spin_lock(ZRAM_LOCK, &zram->table[index].flags);
 }
 
 static void zram_slot_unlock(struct zram *zram, u32 index)
 {
-	bit_spin_unlock(ZRAM_LOCK, &zram->table[index].value);
+	bit_spin_unlock(ZRAM_LOCK, &zram->table[index].flags);
 }
 
 static inline bool init_done(struct zram *zram)
@@ -76,7 +76,7 @@ static inline bool init_done(struct zram *zram)
 static inline bool zram_allocated(struct zram *zram, u32 index)
 {
 
-	return (zram->table[index].value >> (ZRAM_FLAG_SHIFT + 1)) ||
+	return (zram->table[index].flags >> (ZRAM_FLAG_SHIFT + 1)) ||
 					zram->table[index].handle;
 }
 
@@ -99,19 +99,19 @@ static void zram_set_handle(struct zram *zram, u32 index, unsigned long handle)
 static bool zram_test_flag(struct zram *zram, u32 index,
 			enum zram_pageflags flag)
 {
-	return zram->table[index].value & BIT(flag);
+	return zram->table[index].flags & BIT(flag);
 }
 
 static void zram_set_flag(struct zram *zram, u32 index,
 			enum zram_pageflags flag)
 {
-	zram->table[index].value |= BIT(flag);
+	zram->table[index].flags |= BIT(flag);
 }
 
 static void zram_clear_flag(struct zram *zram, u32 index,
 			enum zram_pageflags flag)
 {
-	zram->table[index].value &= ~BIT(flag);
+	zram->table[index].flags &= ~BIT(flag);
 }
 
 static inline void zram_set_element(struct zram *zram, u32 index,
@@ -127,15 +127,15 @@ static unsigned long zram_get_element(struct zram *zram, u32 index)
 
 static size_t zram_get_obj_size(struct zram *zram, u32 index)
 {
-	return zram->table[index].value & (BIT(ZRAM_FLAG_SHIFT) - 1);
+	return zram->table[index].flags & (BIT(ZRAM_FLAG_SHIFT) - 1);
 }
 
 static void zram_set_obj_size(struct zram *zram,
 					u32 index, size_t size)
 {
-	unsigned long flags = zram->table[index].value >> ZRAM_FLAG_SHIFT;
+	unsigned long flags = zram->table[index].flags >> ZRAM_FLAG_SHIFT;
 
-	zram->table[index].value = (flags << ZRAM_FLAG_SHIFT) | size;
+	zram->table[index].flags = (flags << ZRAM_FLAG_SHIFT) | size;
 }
 
 #if PAGE_SIZE != 4096
@@ -282,16 +282,11 @@ static ssize_t mem_used_max_store(struct device *dev,
 }
 
 #ifdef CONFIG_ZRAM_WRITEBACK
-static bool zram_wb_enabled(struct zram *zram)
-{
-	return zram->backing_dev;
-}
-
 static void reset_bdev(struct zram *zram)
 {
 	struct block_device *bdev;
 
-	if (!zram_wb_enabled(zram))
+	if (!zram->backing_dev)
 		return;
 
 	bdev = zram->bdev;
@@ -318,7 +313,7 @@ static ssize_t backing_dev_show(struct device *dev,
 	ssize_t ret;
 
 	down_read(&zram->init_lock);
-	if (!zram_wb_enabled(zram)) {
+	if (!zram->backing_dev) {
 		memcpy(buf, "none\n", 5);
 		up_read(&zram->init_lock);
 		return 5;
@@ -447,7 +442,7 @@ static ssize_t backing_dev_store(struct device *dev,
 	return err;
 }
 
-static unsigned long get_entry_bdev(struct zram *zram)
+static unsigned long alloc_block_bdev(struct zram *zram)
 {
 	unsigned long blk_idx = 1;
 retry:
@@ -462,11 +457,11 @@ static unsigned long get_entry_bdev(struct zram *zram)
 	return blk_idx;
 }
 
-static void put_entry_bdev(struct zram *zram, unsigned long entry)
+static void free_block_bdev(struct zram *zram, unsigned long blk_idx)
 {
 	int was_set;
 
-	was_set = test_and_clear_bit(entry, zram->bitmap);
+	was_set = test_and_clear_bit(blk_idx, zram->bitmap);
 	WARN_ON_ONCE(!was_set);
 }
 
@@ -579,7 +574,7 @@ static int write_to_bdev(struct zram *zram, struct bio_vec *bvec,
 	if (!bio)
 		return -ENOMEM;
 
-	entry = get_entry_bdev(zram);
+	entry = alloc_block_bdev(zram);
 	if (!entry) {
 		bio_put(bio);
 		return -ENOSPC;
@@ -590,7 +585,7 @@ static int write_to_bdev(struct zram *zram, struct bio_vec *bvec,
 	if (!bio_add_page(bio, bvec->bv_page, bvec->bv_len,
 					bvec->bv_offset)) {
 		bio_put(bio);
-		put_entry_bdev(zram, entry);
+		free_block_bdev(zram, entry);
 		return -EIO;
 	}
 
@@ -608,18 +603,7 @@ static int write_to_bdev(struct zram *zram, struct bio_vec *bvec,
 	return 0;
 }
 
-static void zram_wb_clear(struct zram *zram, u32 index)
-{
-	unsigned long entry;
-
-	zram_clear_flag(zram, index, ZRAM_WB);
-	entry = zram_get_element(zram, index);
-	zram_set_element(zram, index, 0);
-	put_entry_bdev(zram, entry);
-}
-
 #else
-static bool zram_wb_enabled(struct zram *zram) { return false; }
 static inline void reset_bdev(struct zram *zram) {};
 static int write_to_bdev(struct zram *zram, struct bio_vec *bvec,
 					u32 index, struct bio *parent,
@@ -634,7 +618,8 @@ static int read_from_bdev(struct zram *zram, struct bio_vec *bvec,
 {
 	return -EIO;
 }
-static void zram_wb_clear(struct zram *zram, u32 index) {}
+
+static void free_block_bdev(struct zram *zram, unsigned long blk_idx) {};
 #endif
 
 #ifdef CONFIG_ZRAM_MEMORY_TRACKING
@@ -656,11 +641,6 @@ static void zram_accessed(struct zram *zram, u32 index)
 	zram->table[index].ac_time = ktime_get_boottime();
 }
 
-static void zram_reset_access(struct zram *zram, u32 index)
-{
-	zram->table[index].ac_time = 0;
-}
-
 static ssize_t read_block_state(struct file *file, char __user *buf,
 				size_t count, loff_t *ppos)
 {
@@ -741,7 +721,6 @@ static void zram_debugfs_unregister(struct zram *zram)
 static void zram_debugfs_create(void) {};
 static void zram_debugfs_destroy(void) {};
 static void zram_accessed(struct zram *zram, u32 index) {};
-static void zram_reset_access(struct zram *zram, u32 index) {};
 static void zram_debugfs_register(struct zram *zram) {};
 static void zram_debugfs_unregister(struct zram *zram) {};
 #endif
@@ -942,17 +921,18 @@ static void zram_free_page(struct zram *zram, size_t index)
 {
 	unsigned long handle;
 
-	zram_reset_access(zram, index);
-
+#ifdef CONFIG_ZRAM_MEMORY_TRACKING
+	zram->table[index].ac_time = 0;
+#endif
 	if (zram_test_flag(zram, index, ZRAM_HUGE)) {
 		zram_clear_flag(zram, index, ZRAM_HUGE);
 		atomic64_dec(&zram->stats.huge_pages);
 	}
 
-	if (zram_wb_enabled(zram) && zram_test_flag(zram, index, ZRAM_WB)) {
-		zram_wb_clear(zram, index);
-		atomic64_dec(&zram->stats.pages_stored);
-		return;
+	if (zram_test_flag(zram, index, ZRAM_WB)) {
+		zram_clear_flag(zram, index, ZRAM_WB);
+		free_block_bdev(zram, zram_get_element(zram, index));
+		goto out;
 	}
 
 	/*
@@ -961,10 +941,8 @@ static void zram_free_page(struct zram *zram, size_t index)
 	 */
 	if (zram_test_flag(zram, index, ZRAM_SAME)) {
 		zram_clear_flag(zram, index, ZRAM_SAME);
-		zram_set_element(zram, index, 0);
 		atomic64_dec(&zram->stats.same_pages);
-		atomic64_dec(&zram->stats.pages_stored);
-		return;
+		goto out;
 	}
 
 	handle = zram_get_handle(zram, index);
@@ -975,10 +953,11 @@ static void zram_free_page(struct zram *zram, size_t index)
 
 	atomic64_sub(zram_get_obj_size(zram, index),
 			&zram->stats.compr_data_size);
+out:
 	atomic64_dec(&zram->stats.pages_stored);
-
 	zram_set_handle(zram, index, 0);
 	zram_set_obj_size(zram, index, 0);
+	WARN_ON_ONCE(zram->table[index].flags & ~(1UL << ZRAM_LOCK));
 }
 
 static int __zram_bvec_read(struct zram *zram, struct page *page, u32 index,
@@ -989,7 +968,6 @@ static int __zram_bvec_read(struct zram *zram, struct page *page, u32 index,
 	unsigned int size;
 	void *src, *dst;
 
-	if (zram_wb_enabled(zram)) {
 	zram_slot_lock(zram, index);
 	if (zram_test_flag(zram, index, ZRAM_WB)) {
 		struct bio_vec bvec;
@@ -1003,10 +981,7 @@ static int __zram_bvec_read(struct zram *zram, struct page *page, u32 index,
 				zram_get_element(zram, index),
 				bio, partial_io);
 	}
-		zram_slot_unlock(zram, index);
-	}
 
-	zram_slot_lock(zram, index);
 	handle = zram_get_handle(zram, index);
 	if (!handle || zram_test_flag(zram, index, ZRAM_SAME)) {
 		unsigned long value;
@@ -1118,7 +1093,7 @@ static int __zram_bvec_write(struct zram *zram, struct bio_vec *bvec,
 
 	if (unlikely(comp_len >= huge_class_size)) {
 		comp_len = PAGE_SIZE;
-		if (zram_wb_enabled(zram) && allow_wb) {
+		if (zram->backing_dev && allow_wb) {
 			zcomp_stream_put(zram->comp);
 			ret = write_to_bdev(zram, bvec, index, bio, &element);
 			if (!ret) {

drivers/block/zram/zram_drv.h

@@ -30,7 +30,7 @@
 
 
 /*
- * The lower ZRAM_FLAG_SHIFT bits of table.value is for
+ * The lower ZRAM_FLAG_SHIFT bits of table.flags is for
  * object size (excluding header), the higher bits is for
  * zram_pageflags.
  *
@@ -41,7 +41,7 @@
  */
 #define ZRAM_FLAG_SHIFT 24
 
-/* Flags for zram pages (table[page_no].value) */
+/* Flags for zram pages (table[page_no].flags) */
 enum zram_pageflags {
 	/* zram slot is locked */
 	ZRAM_LOCK = ZRAM_FLAG_SHIFT,
@@ -60,7 +60,7 @@ struct zram_table_entry {
 		unsigned long handle;
 		unsigned long element;
 	};
-	unsigned long value;
+	unsigned long flags;
 #ifdef CONFIG_ZRAM_MEMORY_TRACKING
 	ktime_t ac_time;
 #endif
@@ -105,8 +105,8 @@ struct zram {
 	 * zram is claimed so open request will be failed
 	 */
 	bool claim; /* Protected by bdev->bd_mutex */
-#ifdef CONFIG_ZRAM_WRITEBACK
 	struct file *backing_dev;
+#ifdef CONFIG_ZRAM_WRITEBACK
 	struct block_device *bdev;
 	unsigned int old_block_size;
 	unsigned long *bitmap;