v4.19.13 snapshot.
diff --git a/fs/btrfs/compression.h b/fs/btrfs/compression.h
new file mode 100644
index 0000000..ddda9b8
--- /dev/null
+++ b/fs/btrfs/compression.h
@@ -0,0 +1,133 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2008 Oracle. All rights reserved.
+ */
+
+#ifndef BTRFS_COMPRESSION_H
+#define BTRFS_COMPRESSION_H
+
+#include <linux/sizes.h>
+
+/*
+ * We want to make sure that amount of RAM required to uncompress an extent is
+ * reasonable, so we limit the total size in ram of a compressed extent to
+ * 128k. This is a crucial number because it also controls how easily we can
+ * spread reads across cpus for decompression.
+ *
+ * We also want to make sure the amount of IO required to do a random read is
+ * reasonably small, so we limit the size of a compressed extent to 128k.
+ */
+
+/* Maximum length of compressed data stored on disk */
+#define BTRFS_MAX_COMPRESSED (SZ_128K)
+/* Maximum size of data before compression */
+#define BTRFS_MAX_UNCOMPRESSED (SZ_128K)
+
+#define BTRFS_ZLIB_DEFAULT_LEVEL 3
+
+struct compressed_bio {
+ /* number of bios pending for this compressed extent */
+ refcount_t pending_bios;
+
+ /* the pages with the compressed data on them */
+ struct page **compressed_pages;
+
+ /* inode that owns this data */
+ struct inode *inode;
+
+ /* starting offset in the inode for our pages */
+ u64 start;
+
+ /* number of bytes in the inode we're working on */
+ unsigned long len;
+
+ /* number of bytes on disk */
+ unsigned long compressed_len;
+
+ /* the compression algorithm for this bio */
+ int compress_type;
+
+ /* number of compressed pages in the array */
+ unsigned long nr_pages;
+
+ /* IO errors */
+ int errors;
+ int mirror_num;
+
+ /* for reads, this is the bio we are copying the data into */
+ struct bio *orig_bio;
+
+ /*
+ * the start of a variable length array of checksums only
+ * used by reads
+ */
+ u32 sums;
+};
+
+void __init btrfs_init_compress(void);
+void __cold btrfs_exit_compress(void);
+
+int btrfs_compress_pages(unsigned int type_level, struct address_space *mapping,
+ u64 start, struct page **pages,
+ unsigned long *out_pages,
+ unsigned long *total_in,
+ unsigned long *total_out);
+int btrfs_decompress(int type, unsigned char *data_in, struct page *dest_page,
+ unsigned long start_byte, size_t srclen, size_t destlen);
+int btrfs_decompress_buf2page(const char *buf, unsigned long buf_start,
+ unsigned long total_out, u64 disk_start,
+ struct bio *bio);
+
+blk_status_t btrfs_submit_compressed_write(struct inode *inode, u64 start,
+ unsigned long len, u64 disk_start,
+ unsigned long compressed_len,
+ struct page **compressed_pages,
+ unsigned long nr_pages,
+ unsigned int write_flags);
+blk_status_t btrfs_submit_compressed_read(struct inode *inode, struct bio *bio,
+ int mirror_num, unsigned long bio_flags);
+
+unsigned btrfs_compress_str2level(const char *str);
+
+enum btrfs_compression_type {
+ BTRFS_COMPRESS_NONE = 0,
+ BTRFS_COMPRESS_ZLIB = 1,
+ BTRFS_COMPRESS_LZO = 2,
+ BTRFS_COMPRESS_ZSTD = 3,
+ BTRFS_COMPRESS_TYPES = 3,
+};
+
+struct btrfs_compress_op {
+ struct list_head *(*alloc_workspace)(void);
+
+ void (*free_workspace)(struct list_head *workspace);
+
+ int (*compress_pages)(struct list_head *workspace,
+ struct address_space *mapping,
+ u64 start,
+ struct page **pages,
+ unsigned long *out_pages,
+ unsigned long *total_in,
+ unsigned long *total_out);
+
+ int (*decompress_bio)(struct list_head *workspace,
+ struct compressed_bio *cb);
+
+ int (*decompress)(struct list_head *workspace,
+ unsigned char *data_in,
+ struct page *dest_page,
+ unsigned long start_byte,
+ size_t srclen, size_t destlen);
+
+ void (*set_level)(struct list_head *ws, unsigned int type);
+};
+
+extern const struct btrfs_compress_op btrfs_zlib_compress;
+extern const struct btrfs_compress_op btrfs_lzo_compress;
+extern const struct btrfs_compress_op btrfs_zstd_compress;
+
+const char* btrfs_compress_type2str(enum btrfs_compression_type type);
+
+int btrfs_compress_heuristic(struct inode *inode, u64 start, u64 end);
+
+#endif