[PATCH v4 3/5] fs/squashfs: add support for ZSTD decompression

[Joao Marcos Costa]

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 at bootlin.com>
---
Changes in v4:
	- Add parameter to sqfs_zstd_decompress().
Changes in v3:
	- Remove memory leak from sqfs_zstd_decompress().
Changes in v2:
	- No changes since last version.
 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 cf388ace58..9457ee5f0f 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 ff2b0b1d34..856cd15e34 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 {
-- 
2.17.1