[RFC][PATCH 4/4] zram: enable zlib backend support

[Sergey Senozhatsky]

Update zram and zcomp read (decompress) path to provide a
zstrm to backends that set ZCOMP_NEED_READ_ZSTRM bit in flags,
so now we can enable ZLIB compression backend in Kconfig.

Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@xxxxxxxxx>
---
 drivers/block/zram/Kconfig    | 14 +++++++++++++-
 drivers/block/zram/zcomp.c    |  7 ++++++-
 drivers/block/zram/zram_drv.c | 23 +++++++++++++++++++----
 3 files changed, 38 insertions(+), 6 deletions(-)

diff --git a/drivers/block/zram/Kconfig b/drivers/block/zram/Kconfig
index 386ba3d..1858762 100644
--- a/drivers/block/zram/Kconfig
+++ b/drivers/block/zram/Kconfig
@@ -23,4 +23,16 @@ config ZRAM_LZ4_COMPRESS
 	default n
 	help
 	  This option enables LZ4 compression algorithm support. Compression
-	  algorithm can be changed using `comp_algorithm' device attribute.
\ No newline at end of file
+	  algorithm can be changed using `comp_algorithm' device attribute.
+
+config ZRAM_ZLIB_COMPRESS
+	bool "Enable ZLIB algorithm support"
+	depends on ZRAM
+	select ZLIB_INFLATE
+	select ZLIB_DEFLATE
+	default n
+	help
+	  This option enables ZLIB compression algorithm support. ZLIB gives
+	  a significantly better compression ratio, at a price of significantly
+	  worse performance. Compression algorithm can be changed using
+	  `comp_algorithm' device attribute.
diff --git a/drivers/block/zram/zcomp.c b/drivers/block/zram/zcomp.c
index a0cef0b..8f24820 100644
--- a/drivers/block/zram/zcomp.c
+++ b/drivers/block/zram/zcomp.c
@@ -323,7 +323,12 @@ int zcomp_decompress(struct zcomp *comp, struct zcomp_strm *zstrm,
 		const unsigned char *src,
 		size_t src_len, unsigned char *dst)
 {
-	return comp->backend->decompress(src, src_len, dst, NULL);
+	void *private = NULL;
+
+	if (unlikely(zstrm))
+		private = zstrm->private;
+
+	return comp->backend->decompress(src, src_len, dst, private);
 }
 
 void zcomp_destroy(struct zcomp *comp)
diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index 0aec4ce..5c52400 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -560,7 +560,8 @@ static void zram_free_page(struct zram *zram, size_t index)
 	zram_set_obj_size(meta, index, 0);
 }
 
-static int zram_decompress_page(struct zram *zram, char *mem, u32 index)
+static int zram_decompress_page(struct zram *zram, struct zcomp_strm *zstrm,
+		char *mem, u32 index)
 {
 	int ret = 0;
 	unsigned char *cmem;
@@ -582,7 +583,7 @@ static int zram_decompress_page(struct zram *zram, char *mem, u32 index)
 	if (size == PAGE_SIZE)
 		copy_page(mem, cmem);
 	else
-		ret = zcomp_decompress(zram->comp, NULL, cmem, size, mem);
+		ret = zcomp_decompress(zram->comp, zstrm, cmem, size, mem);
 	zs_unmap_object(meta->mem_pool, handle);
 	bit_spin_unlock(ZRAM_ACCESS, &meta->table[index].value);
 
@@ -602,6 +603,7 @@ static int zram_bvec_read(struct zram *zram, struct bio_vec *bvec,
 	struct page *page;
 	unsigned char *user_mem, *uncmem = NULL;
 	struct zram_meta *meta = zram->meta;
+	void *dzstrm;
 	page = bvec->bv_page;
 
 	bit_spin_lock(ZRAM_ACCESS, &meta->table[index].value);
@@ -617,6 +619,7 @@ static int zram_bvec_read(struct zram *zram, struct bio_vec *bvec,
 		/* Use  a temporary buffer to decompress the page */
 		uncmem = kmalloc(PAGE_SIZE, GFP_NOIO);
 
+	dzstrm = zcomp_decompress_begin(zram->comp);
 	user_mem = kmap_atomic(page);
 	if (!is_partial_io(bvec))
 		uncmem = user_mem;
@@ -627,7 +630,11 @@ static int zram_bvec_read(struct zram *zram, struct bio_vec *bvec,
 		goto out_cleanup;
 	}
 
-	ret = zram_decompress_page(zram, uncmem, index);
+	ret = zram_decompress_page(zram, dzstrm, uncmem, index);
+
+	zcomp_decompress_end(zram->comp, dzstrm);
+	dzstrm = NULL;
+
 	/* Should NEVER happen. Return bio error if it does. */
 	if (unlikely(ret))
 		goto out_cleanup;
@@ -638,10 +645,13 @@ static int zram_bvec_read(struct zram *zram, struct bio_vec *bvec,
 
 	flush_dcache_page(page);
 	ret = 0;
+
 out_cleanup:
 	kunmap_atomic(user_mem);
+	zcomp_decompress_end(zram->comp, dzstrm);
 	if (is_partial_io(bvec))
 		kfree(uncmem);
+
 	return ret;
 }
 
@@ -659,6 +669,8 @@ static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index,
 
 	page = bvec->bv_page;
 	if (is_partial_io(bvec)) {
+		void *dzstrm;
+
 		/*
 		 * This is a partial IO. We need to read the full page
 		 * before to write the changes.
@@ -668,7 +680,10 @@ static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index,
 			ret = -ENOMEM;
 			goto out;
 		}
-		ret = zram_decompress_page(zram, uncmem, index);
+
+		dzstrm = zcomp_decompress_begin(zram->comp);
+		ret = zram_decompress_page(zram, dzstrm, uncmem, index);
+		zcomp_decompress_end(zram->comp, dzstrm);
 		if (ret)
 			goto out;
 	}
-- 
2.5.0

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