1 files changed, 105 insertions, 0 deletions
diff --git a/fs/erofs/compress.h b/fs/erofs/compress.h
new file mode 100644
index 0000000000..279933e007
--- /dev/null
+++ b/fs/erofs/compress.h
@@ -0,0 +1,105 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (C) 2019 HUAWEI, Inc.
+ *             https://www.huawei.com/
+ */
+#ifndef __EROFS_FS_COMPRESS_H
+#define __EROFS_FS_COMPRESS_H
+
+#include "internal.h"
+
+struct z_erofs_decompress_req {
+	struct super_block *sb;
+	struct page **in, **out;
+
+	unsigned short pageofs_in, pageofs_out;
+	unsigned int inputsize, outputsize;
+
+	/* indicate the algorithm will be used for decompression */
+	unsigned int alg;
+	bool inplace_io, partial_decoding, fillgaps;
+};
+
+struct z_erofs_decompressor {
+	int (*config)(struct super_block *sb, struct erofs_super_block *dsb,
+		      void *data, int size);
+	int (*decompress)(struct z_erofs_decompress_req *rq,
+			  struct page **pagepool);
+	char *name;
+};
+
+/* some special page->private (unsigned long, see below) */
+#define Z_EROFS_SHORTLIVED_PAGE		(-1UL << 2)
+#define Z_EROFS_PREALLOCATED_PAGE	(-2UL << 2)
+
+/*
+ * For all pages in a pcluster, page->private should be one of
+ * Type                         Last 2bits      page->private
+ * short-lived page             00              Z_EROFS_SHORTLIVED_PAGE
+ * preallocated page (tryalloc) 00              Z_EROFS_PREALLOCATED_PAGE
+ * cached/managed page          00              pointer to z_erofs_pcluster
+ * online page (file-backed,    01/10/11        sub-index << 2 | count
+ *              some pages can be used for inplace I/O)
+ *
+ * page->mapping should be one of
+ * Type                 page->mapping
+ * short-lived page     NULL
+ * preallocated page    NULL
+ * cached/managed page  non-NULL or NULL (invalidated/truncated page)
+ * online page          non-NULL
+ *
+ * For all managed pages, PG_private should be set with 1 extra refcount,
+ * which is used for page reclaim / migration.
+ */
+
+/*
+ * short-lived pages are pages directly from buddy system with specific
+ * page->private (no need to set PagePrivate since these are non-LRU /
+ * non-movable pages and bypass reclaim / migration code).
+ */
+static inline bool z_erofs_is_shortlived_page(struct page *page)
+{
+	if (page->private != Z_EROFS_SHORTLIVED_PAGE)
+		return false;
+
+	DBG_BUGON(page->mapping);
+	return true;
+}
+
+static inline bool z_erofs_put_shortlivedpage(struct page **pagepool,
+					      struct page *page)
+{
+	if (!z_erofs_is_shortlived_page(page))
+		return false;
+
+	/* short-lived pages should not be used by others at the same time */
+	if (page_ref_count(page) > 1) {
+		put_page(page);
+	} else {
+		/* follow the pcluster rule above. */
+		erofs_pagepool_add(pagepool, page);
+	}
+	return true;
+}
+
+#define MNGD_MAPPING(sbi)	((sbi)->managed_cache->i_mapping)
+static inline bool erofs_page_is_managed(const struct erofs_sb_info *sbi,
+					 struct page *page)
+{
+	return page->mapping == MNGD_MAPPING(sbi);
+}
+
+int z_erofs_fixup_insize(struct z_erofs_decompress_req *rq, const char *padbuf,
+			 unsigned int padbufsize);
+extern const struct z_erofs_decompressor erofs_decompressors[];
+
+/* prototypes for specific algorithms */
+int z_erofs_load_lzma_config(struct super_block *sb,
+			struct erofs_super_block *dsb, void *data, int size);
+int z_erofs_load_deflate_config(struct super_block *sb,
+			struct erofs_super_block *dsb, void *data, int size);
+int z_erofs_lzma_decompress(struct z_erofs_decompress_req *rq,
+			    struct page **pagepool);
+int z_erofs_deflate_decompress(struct z_erofs_decompress_req *rq,
+			       struct page **pagepool);
+#endif