Revert "zram: implement deduplication in zram"

This reverts commit b96fb270ce.

Bug: 129372836
Change-Id: I32c6bd4b0ab7fa9a4896c2d7e92057305b200e3a
Signed-off-by: Minchan Kim <minchan@google.com>
Signed-off-by: UtsavBalar1231 <utsavbalar1231@gmail.com>

Documentation/blockdev/zram.txt

@@ -221,8 +221,6 @@ line of text and contains the following stats separated by whitespace:
  same_pages       the number of same element filled pages written to this disk.
                   No memory is allocated for such pages.
  pages_compacted  the number of pages freed during compaction
- dup_data_size	  deduplicated data size
- meta_data_size	  the amount of metadata allocated for deduplication feature
  huge_pages	  the number of incompressible pages
 
 File /sys/block/zram<id>/bd_stat

drivers/block/zram/Makefile

@@ -1,3 +1,3 @@
-zram-y	:=	zcomp.o zram_drv.o zram_dedup.o
+zram-y	:=	zcomp.o zram_drv.o
 
 obj-$(CONFIG_ZRAM)	+=	zram.o

drivers/block/zram/zram_dedup.c

@@ -1,204 +0,0 @@
-/*
- * Copyright (C) 2017 Joonsoo Kim.
- *
- * This program is free software; you can redistribute it and/or
- * modify it under the terms of the GNU General Public License
- * as published by the Free Software Foundation; either version
- * 2 of the License, or (at your option) any later version.
- */
-
-#include <linux/vmalloc.h>
-#include <linux/jhash.h>
-#include <linux/highmem.h>
-
-#include "zram_drv.h"
-
-/* One slot will contain 128 pages theoretically */
-#define ZRAM_HASH_SHIFT		7
-#define ZRAM_HASH_SIZE_MIN	(1 << 10)
-#define ZRAM_HASH_SIZE_MAX	(1 << 31)
-
-u64 zram_dedup_dup_size(struct zram *zram)
-{
-	return (u64)atomic64_read(&zram->stats.dup_data_size);
-}
-
-u64 zram_dedup_meta_size(struct zram *zram)
-{
-	return (u64)atomic64_read(&zram->stats.meta_data_size);
-}
-
-static u32 zram_dedup_checksum(unsigned char *mem)
-{
-	return jhash(mem, PAGE_SIZE, 0);
-}
-
-void zram_dedup_insert(struct zram *zram, struct zram_entry *new,
-				u32 checksum)
-{
-	struct zram_hash *hash;
-	struct rb_root *rb_root;
-	struct rb_node **rb_node, *parent = NULL;
-	struct zram_entry *entry;
-
-	new->checksum = checksum;
-	hash = &zram->hash[checksum % zram->hash_size];
-	rb_root = &hash->rb_root;
-
-	spin_lock(&hash->lock);
-	rb_node = &rb_root->rb_node;
-	while (*rb_node) {
-		parent = *rb_node;
-		entry = rb_entry(parent, struct zram_entry, rb_node);
-		if (checksum < entry->checksum)
-			rb_node = &parent->rb_left;
-		else if (checksum > entry->checksum)
-			rb_node = &parent->rb_right;
-		else
-			rb_node = &parent->rb_left;
-	}
-
-	rb_link_node(&new->rb_node, parent, rb_node);
-	rb_insert_color(&new->rb_node, rb_root);
-	spin_unlock(&hash->lock);
-}
-
-static bool zram_dedup_match(struct zram *zram, struct zram_entry *entry,
-				unsigned char *mem)
-{
-	bool match = false;
-	unsigned char *cmem;
-	struct zcomp_strm *zstrm;
-
-	cmem = zs_map_object(zram->mem_pool, entry->handle, ZS_MM_RO);
-	if (entry->len == PAGE_SIZE) {
-		match = !memcmp(mem, cmem, PAGE_SIZE);
-	} else {
-		zstrm = zcomp_stream_get(zram->comp);
-		if (!zcomp_decompress(zstrm, cmem, entry->len, zstrm->buffer))
-			match = !memcmp(mem, zstrm->buffer, PAGE_SIZE);
-		zcomp_stream_put(zram->comp);
-	}
-	zs_unmap_object(zram->mem_pool, entry->handle);
-
-	return match;
-}
-
-static unsigned long zram_dedup_put(struct zram *zram,
-				struct zram_entry *entry)
-{
-	struct zram_hash *hash;
-	u32 checksum;
-
-	checksum = entry->checksum;
-	hash = &zram->hash[checksum % zram->hash_size];
-
-	spin_lock(&hash->lock);
-
-	entry->refcount--;
-	if (!entry->refcount)
-		rb_erase(&entry->rb_node, &hash->rb_root);
-	else
-		atomic64_sub(entry->len, &zram->stats.dup_data_size);
-
-	spin_unlock(&hash->lock);
-
-	return entry->refcount;
-}
-
-static struct zram_entry *zram_dedup_get(struct zram *zram,
-				unsigned char *mem, u32 checksum)
-{
-	struct zram_hash *hash;
-	struct zram_entry *entry;
-	struct rb_node *rb_node;
-
-	hash = &zram->hash[checksum % zram->hash_size];
-
-	spin_lock(&hash->lock);
-	rb_node = hash->rb_root.rb_node;
-	while (rb_node) {
-		entry = rb_entry(rb_node, struct zram_entry, rb_node);
-		if (checksum == entry->checksum) {
-			entry->refcount++;
-			atomic64_add(entry->len, &zram->stats.dup_data_size);
-			spin_unlock(&hash->lock);
-
-			if (zram_dedup_match(zram, entry, mem))
-				return entry;
-
-			zram_entry_free(zram, entry);
-
-			return NULL;
-		}
-
-		if (checksum < entry->checksum)
-			rb_node = rb_node->rb_left;
-		else
-			rb_node = rb_node->rb_right;
-	}
-	spin_unlock(&hash->lock);
-
-	return NULL;
-}
-
-struct zram_entry *zram_dedup_find(struct zram *zram, struct page *page,
-				u32 *checksum)
-{
-	void *mem;
-	struct zram_entry *entry;
-
-	mem = kmap_atomic(page);
-	*checksum = zram_dedup_checksum(mem);
-
-	entry = zram_dedup_get(zram, mem, *checksum);
-	kunmap_atomic(mem);
-
-	return entry;
-}
-
-void zram_dedup_init_entry(struct zram *zram, struct zram_entry *entry,
-				unsigned long handle, unsigned int len)
-{
-	entry->handle = handle;
-	entry->refcount = 1;
-	entry->len = len;
-}
-
-bool zram_dedup_put_entry(struct zram *zram, struct zram_entry *entry)
-{
-	if (zram_dedup_put(zram, entry))
-		return false;
-
-	return true;
-}
-
-int zram_dedup_init(struct zram *zram, size_t num_pages)
-{
-	int i;
-	struct zram_hash *hash;
-
-	zram->hash_size = num_pages >> ZRAM_HASH_SHIFT;
-	zram->hash_size = min_t(size_t, ZRAM_HASH_SIZE_MAX, zram->hash_size);
-	zram->hash_size = max_t(size_t, ZRAM_HASH_SIZE_MIN, zram->hash_size);
-	zram->hash = vzalloc(zram->hash_size * sizeof(struct zram_hash));
-	if (!zram->hash) {
-		pr_err("Error allocating zram entry hash\n");
-		return -ENOMEM;
-	}
-
-	for (i = 0; i < zram->hash_size; i++) {
-		hash = &zram->hash[i];
-		spin_lock_init(&hash->lock);
-		hash->rb_root = RB_ROOT;
-	}
-
-	return 0;
-}
-
-void zram_dedup_fini(struct zram *zram)
-{
-	vfree(zram->hash);
-	zram->hash = NULL;
-	zram->hash_size = 0;
-}

drivers/block/zram/zram_dedup.h

@@ -1,22 +0,0 @@
-#ifndef _ZRAM_DEDUP_H_
-#define _ZRAM_DEDUP_H_
-
-struct zram;
-struct zram_entry;
-
-u64 zram_dedup_dup_size(struct zram *zram);
-u64 zram_dedup_meta_size(struct zram *zram);
-
-void zram_dedup_insert(struct zram *zram, struct zram_entry *new,
-				u32 checksum);
-struct zram_entry *zram_dedup_find(struct zram *zram, struct page *page,
-				u32 *checksum);
-
-void zram_dedup_init_entry(struct zram *zram, struct zram_entry *entry,
-				unsigned long handle, unsigned int len);
-bool zram_dedup_put_entry(struct zram *zram, struct zram_entry *entry);
-
-int zram_dedup_init(struct zram *zram, size_t num_pages);
-void zram_dedup_fini(struct zram *zram);
-
-#endif /* _ZRAM_DEDUP_H_ */

drivers/block/zram/zram_drv.c

@@ -1074,7 +1074,7 @@ static ssize_t mm_stat_show(struct device *dev,
 	max_used = atomic_long_read(&zram->stats.max_used_pages);
 
 	ret = scnprintf(buf, PAGE_SIZE,
-			"%8llu %8llu %8llu %8lu %8ld %8llu %8lu %8llu %8llu %8llu\n",
+			"%8llu %8llu %8llu %8lu %8ld %8llu %8lu %8llu\n",
 			orig_size << PAGE_SHIFT,
 			(u64)atomic64_read(&zram->stats.compr_data_size),
 			mem_used << PAGE_SHIFT,
@@ -1082,8 +1082,6 @@ static ssize_t mm_stat_show(struct device *dev,
 			max_used << PAGE_SHIFT,
 			(u64)atomic64_read(&zram->stats.same_pages),
 			pool_stats.pages_compacted,
-			zram_dedup_dup_size(zram),
-			zram_dedup_meta_size(zram),
 			(u64)atomic64_read(&zram->stats.huge_pages));
 	up_read(&zram->init_lock);
 
@@ -1139,34 +1137,26 @@ static struct zram_entry *zram_entry_alloc(struct zram *zram,
 					   unsigned int len, gfp_t flags)
 {
 	struct zram_entry *entry;
-	unsigned long handle;
 
 	entry = kzalloc(sizeof(*entry),
 			flags & ~(__GFP_HIGHMEM|__GFP_MOVABLE|__GFP_CMA));
 	if (!entry)
 		return NULL;
 
-	handle = zs_malloc(zram->mem_pool, len, flags);
-	if (!handle) {
+	entry->handle = zs_malloc(zram->mem_pool, len, flags);
+	if (!entry->handle) {
 		kfree(entry);
 		return NULL;
 	}
 
-	zram_dedup_init_entry(zram, entry, handle, len);
-	atomic64_add(sizeof(*entry), &zram->stats.meta_data_size);
-
 	return entry;
 }
 
-void zram_entry_free(struct zram *zram, struct zram_entry *entry)
+static inline void zram_entry_free(struct zram *zram,
+				   struct zram_entry *entry)
 {
-	if (!zram_dedup_put_entry(zram, entry))
-		return;
-
 	zs_free(zram->mem_pool, entry->handle);
 	kfree(entry);
-
-	atomic64_sub(sizeof(*entry), &zram->stats.meta_data_size);
 }
 
 static void zram_meta_free(struct zram *zram, u64 disksize)
@@ -1179,7 +1169,6 @@ static void zram_meta_free(struct zram *zram, u64 disksize)
 		zram_free_page(zram, index);
 
 	zs_destroy_pool(zram->mem_pool);
-	zram_dedup_fini(zram);
 	vfree(zram->table);
 }
 
@@ -1201,12 +1190,6 @@ static bool zram_meta_alloc(struct zram *zram, u64 disksize)
 	if (!huge_class_size)
 		huge_class_size = zs_huge_class_size(zram->mem_pool);
 
-	if (zram_dedup_init(zram, num_pages)) {
-		vfree(zram->table);
-		zs_destroy_pool(zram->mem_pool);
-		return false;
-	}
-
 	return true;
 }
 
@@ -1366,7 +1349,6 @@ static int __zram_bvec_write(struct zram *zram, struct bio_vec *bvec,
 	void *src, *dst, *mem;
 	struct zcomp_strm *zstrm;
 	struct page *page = bvec->bv_page;
-	u32 checksum;
 	unsigned long element = 0;
 	enum zram_pageflags flags = 0;
 
@@ -1380,12 +1362,6 @@ static int __zram_bvec_write(struct zram *zram, struct bio_vec *bvec,
 	}
 	kunmap_atomic(mem);
 
-	entry = zram_dedup_find(zram, page, &checksum);
-	if (entry) {
-		comp_len = entry->len;
-		goto out;
-	}
-
 compress_again:
 	zstrm = zcomp_stream_get(zram->comp);
 	src = kmap_atomic(page);
@@ -1454,7 +1430,6 @@ compress_again:
 	zcomp_stream_put(zram->comp);
 	zs_unmap_object(zram->mem_pool, entry->handle);
 	atomic64_add(comp_len, &zram->stats.compr_data_size);
-	zram_dedup_insert(zram, entry, checksum);
 out:
 	/*
 	 * Free memory associated with this sector

drivers/block/zram/zram_drv.h

@@ -18,10 +18,8 @@
 #include <linux/rwsem.h>
 #include <linux/zsmalloc.h>
 #include <linux/crypto.h>
-#include <linux/spinlock.h>
 
 #include "zcomp.h"
-#include "zram_dedup.h"
 
 #define SECTOR_SHIFT		9
 #define SECTORS_PER_PAGE_SHIFT	(PAGE_SHIFT - SECTOR_SHIFT)
@@ -60,10 +58,6 @@ enum zram_pageflags {
 /*-- Data structures */
 
 struct zram_entry {
-	struct rb_node rb_node;
-	u32 len;
-	u32 checksum;
-	unsigned long refcount;
 	unsigned long handle;
 };
 
@@ -92,11 +86,6 @@ struct zram_stats {
 	atomic64_t pages_stored;	/* no. of pages currently stored */
 	atomic_long_t max_used_pages;	/* no. of maximum pages stored */
 	atomic64_t writestall;		/* no. of write slow paths */
-	atomic64_t dup_data_size;	/*
-					 * compressed size of pages
-					 * duplicated
-					 */
-	atomic64_t meta_data_size;	/* size of zram_entries */
 	atomic64_t miss_free;		/* no. of missed free */
 #ifdef	CONFIG_ZRAM_WRITEBACK
 	atomic64_t bd_count;		/* no. of pages in backing device */
@@ -105,18 +94,11 @@ struct zram_stats {
 #endif
 };
 
-struct zram_hash {
-	spinlock_t lock;
-	struct rb_root rb_root;
-};
-
 struct zram {
 	struct zram_table_entry *table;
 	struct zs_pool *mem_pool;
 	struct zcomp *comp;
 	struct gendisk *disk;
-	struct zram_hash *hash;
-	size_t hash_size;
 	/* Prevent concurrent execution of device init */
 	struct rw_semaphore init_lock;
 	/*
@@ -149,6 +131,4 @@ struct zram {
 	struct dentry *debugfs_dir;
 #endif
 };
-
-void zram_entry_free(struct zram *zram, struct zram_entry *entry);
 #endif