[RFC][PATCH 2/4] zram: extend zcomp_backend decompress callback

[Sergey Senozhatsky <sergey.senozhatsky@gmail.com>]

This is a preparation patch to make ZLIB compression backend
support possible. ZLIB requires zstrm both for compress and
decompress operations, which is not needed for LZO and LZ4
backends. Extend zcomp_decompress() and zcomp_backend decompress
callback to optionally accept zstrm pointer. Pass NULL as
a zstrm pointer to LZO and LZ4 backends.

Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
---
 drivers/block/zram/zcomp.c     | 5 +++--
 drivers/block/zram/zcomp.h     | 5 +++--
 drivers/block/zram/zcomp_lz4.c | 2 +-
 drivers/block/zram/zcomp_lzo.c | 2 +-
 drivers/block/zram/zram_drv.c  | 2 +-
 5 files changed, 9 insertions(+), 7 deletions(-)

diff --git a/drivers/block/zram/zcomp.c b/drivers/block/zram/zcomp.c
index 61e06b4..a1c67be 100644
--- a/drivers/block/zram/zcomp.c
+++ b/drivers/block/zram/zcomp.c
@@ -313,10 +313,11 @@ int zcomp_compress(struct zcomp *comp, struct zcomp_strm *zstrm,
 			zstrm->private);
 }
 
-int zcomp_decompress(struct zcomp *comp, const unsigned char *src,
+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);
+	return comp->backend->decompress(src, src_len, dst, NULL);
 }
 
 void zcomp_destroy(struct zcomp *comp)
diff --git a/drivers/block/zram/zcomp.h b/drivers/block/zram/zcomp.h
index b8cf0b0..5cb9a0b 100644
--- a/drivers/block/zram/zcomp.h
+++ b/drivers/block/zram/zcomp.h
@@ -31,7 +31,7 @@ struct zcomp_backend {
 			size_t *dst_len, void *private);
 
 	int (*decompress)(const unsigned char *src, size_t src_len,
-			unsigned char *dst);
+			unsigned char *dst, void *private);
 
 	int (*flags)(void);
 
@@ -67,7 +67,8 @@ void zcomp_strm_release(struct zcomp *comp, struct zcomp_strm *zstrm);
 int zcomp_compress(struct zcomp *comp, struct zcomp_strm *zstrm,
 		const unsigned char *src, size_t *dst_len);
 
-int zcomp_decompress(struct zcomp *comp, const unsigned char *src,
+int zcomp_decompress(struct zcomp *comp, struct zcomp_strm *zstrm,
+		const unsigned char *src,
 		size_t src_len, unsigned char *dst);
 
 bool zcomp_set_max_streams(struct zcomp *comp, int num_strm);
diff --git a/drivers/block/zram/zcomp_lz4.c b/drivers/block/zram/zcomp_lz4.c
index 99ed995..09bf30c 100644
--- a/drivers/block/zram/zcomp_lz4.c
+++ b/drivers/block/zram/zcomp_lz4.c
@@ -36,7 +36,7 @@ static int zcomp_lz4_compress(const unsigned char *src, unsigned char *dst,
 }
 
 static int zcomp_lz4_decompress(const unsigned char *src, size_t src_len,
-		unsigned char *dst)
+		unsigned char *dst, void *private)
 {
 	size_t dst_len = PAGE_SIZE;
 	/* return  : Success if return 0 */
diff --git a/drivers/block/zram/zcomp_lzo.c b/drivers/block/zram/zcomp_lzo.c
index 7572d92..9cc2fa4 100644
--- a/drivers/block/zram/zcomp_lzo.c
+++ b/drivers/block/zram/zcomp_lzo.c
@@ -36,7 +36,7 @@ static int lzo_compress(const unsigned char *src, unsigned char *dst,
 }
 
 static int lzo_decompress(const unsigned char *src, size_t src_len,
-		unsigned char *dst)
+		unsigned char *dst, void *private)
 {
 	size_t dst_len = PAGE_SIZE;
 	int ret = lzo1x_decompress_safe(src, src_len, dst, &dst_len);
diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index 509023f..0aec4ce 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -582,7 +582,7 @@ 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, cmem, size, mem);
+		ret = zcomp_decompress(zram->comp, NULL, cmem, size, mem);
 	zs_unmap_object(meta->mem_pool, handle);
 	bit_spin_unlock(ZRAM_ACCESS, &meta->table[index].value);
 
-- 
2.5.0