[PATCH v5 8/9] lib: unzstd: Switch to the zstd-1.4.6 API

[Nick Terrell <nickrterrell@gmail.com>]

From: Nick Terrell <terrelln@fb.com>

Move away from the compatibility wrapper to the zstd-1.4.6 API. This
code is functionally equivalent.

Signed-off-by: Nick Terrell <terrelln@fb.com>
---
 lib/decompress_unzstd.c | 40 ++++++++++++++--------------------------
 1 file changed, 14 insertions(+), 26 deletions(-)

diff --git a/lib/decompress_unzstd.c b/lib/decompress_unzstd.c
index 3c6ad01ffcd5..efbe66501b34 100644
--- a/lib/decompress_unzstd.c
+++ b/lib/decompress_unzstd.c
@@ -73,7 +73,8 @@
 
 #include <linux/decompress/mm.h>
 #include <linux/kernel.h>
-#include <linux/zstd_compat.h>
+#include <linux/zstd.h>
+#include <linux/zstd_errors.h>
 
 /* 128MB is the maximum window size supported by zstd. */
 #define ZSTD_WINDOWSIZE_MAX	(1 << ZSTD_WINDOWLOG_MAX)
@@ -120,9 +121,9 @@ static int INIT decompress_single(const u8 *in_buf, long in_len, u8 *out_buf,
 				  long out_len, long *in_pos,
 				  void (*error)(char *x))
 {
-	const size_t wksp_size = ZSTD_DCtxWorkspaceBound();
+	const size_t wksp_size = ZSTD_estimateDCtxSize();
 	void *wksp = large_malloc(wksp_size);
-	ZSTD_DCtx *dctx = ZSTD_initDCtx(wksp, wksp_size);
+	ZSTD_DCtx *dctx = ZSTD_initStaticDCtx(wksp, wksp_size);
 	int err;
 	size_t ret;
 
@@ -165,7 +166,6 @@ static int INIT __unzstd(unsigned char *in_buf, long in_len,
 {
 	ZSTD_inBuffer in;
 	ZSTD_outBuffer out;
-	ZSTD_frameParams params;
 	void *in_allocated = NULL;
 	void *out_allocated = NULL;
 	void *wksp = NULL;
@@ -234,36 +234,24 @@ static int INIT __unzstd(unsigned char *in_buf, long in_len,
 	out.size = out_len;
 
 	/*
-	 * We need to know the window size to allocate the ZSTD_DStream.
-	 * Since we are streaming, we need to allocate a buffer for the sliding
-	 * window. The window size varies from 1 KB to ZSTD_WINDOWSIZE_MAX
-	 * (8 MB), so it is important to use the actual value so as not to
-	 * waste memory when it is smaller.
+	 * Zstd determines the workspace size from the window size written
+	 * into the frame header. This ensures that we use the minimum value
+	 * possible, since the window size varies from 1 KB to ZSTD_WINDOWSIZE_MAX
+	 * (1 GB), so it is very important to use the actual value.
 	 */
-	ret = ZSTD_getFrameParams(&params, in.src, in.size);
+	wksp_size = ZSTD_estimateDStreamSize_fromFrame(in.src, in.size);
 	err = handle_zstd_error(ret, error);
 	if (err)
 		goto out;
-	if (ret != 0) {
-		error("ZSTD-compressed data has an incomplete frame header");
-		err = -1;
-		goto out;
-	}
-	if (params.windowSize > ZSTD_WINDOWSIZE_MAX) {
-		error("ZSTD-compressed data has too large a window size");
+	wksp = large_malloc(wksp_size);
+	if (wksp == NULL) {
+		error("Out of memory while allocating ZSTD_DStream");
 		err = -1;
 		goto out;
 	}
-
-	/*
-	 * Allocate the ZSTD_DStream now that we know how much memory is
-	 * required.
-	 */
-	wksp_size = ZSTD_DStreamWorkspaceBound(params.windowSize);
-	wksp = large_malloc(wksp_size);
-	dstream = ZSTD_initDStream(params.windowSize, wksp, wksp_size);
+	dstream = ZSTD_initStaticDStream(wksp, wksp_size);
 	if (dstream == NULL) {
-		error("Out of memory while allocating ZSTD_DStream");
+		error("ZSTD_initStaticDStream failed");
 		err = -1;
 		goto out;
 	}
-- 
2.28.0