From 9c948f536fec115b590760c2e9e333945dfde990 Mon Sep 17 00:00:00 2001
From: Joao Marcos Costa <joaomarcos.costa@bootlin.com>
Date: Tue, 18 Aug 2020 17:17:23 +0200
Subject: [PATCH] fs/squashfs: add support for ZSTD decompression

Add call to ZSTD's ZSTD_decompressDCtx(). In this use case, the caller
can upper bound the decompressed size, which will be the SquashFS data
block (or metadata block) size, so there is no need to use streaming
API. Add ZSTD's worskpace to squashfs_ctxt structure.

Signed-off-by: Joao Marcos Costa <joaomarcos.costa@bootlin.com>
---
 fs/squashfs/sqfs_decompressor.c | 42 +++++++++++++++++++++++++++++++++
 fs/squashfs/sqfs_filesystem.h   |  3 +++
 2 files changed, 45 insertions(+)

diff --git a/fs/squashfs/sqfs_decompressor.c b/fs/squashfs/sqfs_decompressor.c
index cf388ace587..9457ee5f0f9 100644
--- a/fs/squashfs/sqfs_decompressor.c
+++ b/fs/squashfs/sqfs_decompressor.c
@@ -13,6 +13,10 @@
 #include <u-boot/zlib.h>
 #endif
 
+#if IS_ENABLED(CONFIG_ZSTD)
+#include <linux/zstd.h>
+#endif
+
 #include "sqfs_decompressor.h"
 #include "sqfs_utils.h"
 
@@ -24,6 +28,13 @@ int sqfs_decompressor_init(struct squashfs_ctxt *ctxt)
 #if IS_ENABLED(CONFIG_ZLIB)
 	case SQFS_COMP_ZLIB:
 		break;
+#endif
+#if IS_ENABLED(CONFIG_ZSTD)
+	case SQFS_COMP_ZSTD:
+		ctxt->zstd_workspace = malloc(ZSTD_DCtxWorkspaceBound());
+		if (!ctxt->zstd_workspace)
+			return -ENOMEM;
+		break;
 #endif
 	default:
 		printf("Error: unknown compression type.\n");
@@ -41,6 +52,11 @@ void sqfs_decompressor_cleanup(struct squashfs_ctxt *ctxt)
 #if IS_ENABLED(CONFIG_ZLIB)
 	case SQFS_COMP_ZLIB:
 		break;
+#endif
+#if IS_ENABLED(CONFIG_ZSTD)
+	case SQFS_COMP_ZSTD:
+		free(ctxt->zstd_workspace);
+		break;
 #endif
 	}
 }
@@ -62,6 +78,22 @@ static void zlib_decompression_status(int ret)
 }
 #endif
 
+#if IS_ENABLED(CONFIG_ZSTD)
+static int sqfs_zstd_decompress(struct squashfs_ctxt *ctxt, void *dest,
+				unsigned long dest_len, void *source, u32 src_len)
+{
+	ZSTD_DCtx *ctx;
+	size_t wsize;
+	int ret;
+
+	wsize = ZSTD_DCtxWorkspaceBound();
+	ctx = ZSTD_initDCtx(ctxt->zstd_workspace, wsize);
+	ret = ZSTD_decompressDCtx(ctx, dest, dest_len, source, src_len);
+
+	return ZSTD_isError(ret);
+}
+#endif /* CONFIG_ZSTD */
+
 int sqfs_decompress(struct squashfs_ctxt *ctxt, void *dest,
 		    unsigned long *dest_len, void *source, u32 src_len)
 {
@@ -79,6 +111,16 @@ int sqfs_decompress(struct squashfs_ctxt *ctxt, void *dest,
 
 		break;
 #endif
+#if IS_ENABLED(CONFIG_ZSTD)
+	case SQFS_COMP_ZSTD:
+		ret = sqfs_zstd_decompress(ctxt, dest, *dest_len, source, src_len);
+		if (ret) {
+			printf("ZSTD Error code: %d\n", ZSTD_getErrorCode(ret));
+			return -EINVAL;
+		}
+
+		break;
+#endif
 	default:
 		printf("Error: unknown compression type.\n");
 		return -EINVAL;
diff --git a/fs/squashfs/sqfs_filesystem.h b/fs/squashfs/sqfs_filesystem.h
index ff2b0b1d34e..856cd15e349 100644
--- a/fs/squashfs/sqfs_filesystem.h
+++ b/fs/squashfs/sqfs_filesystem.h
@@ -77,6 +77,9 @@ struct squashfs_ctxt {
 	struct disk_partition cur_part_info;
 	struct blk_desc *cur_dev;
 	struct squashfs_super_block *sblk;
+#if IS_ENABLED(CONFIG_ZSTD)
+	void *zstd_workspace;
+#endif
 };
 
 struct squashfs_directory_index {