v4.19.13 snapshot.
diff --git a/fs/btrfs/struct-funcs.c b/fs/btrfs/struct-funcs.c
new file mode 100644
index 0000000..4c13b73
--- /dev/null
+++ b/fs/btrfs/struct-funcs.c
@@ -0,0 +1,129 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2007 Oracle. All rights reserved.
+ */
+
+#include <asm/unaligned.h>
+
+#include "ctree.h"
+
+static inline u8 get_unaligned_le8(const void *p)
+{
+ return *(u8 *)p;
+}
+
+static inline void put_unaligned_le8(u8 val, void *p)
+{
+ *(u8 *)p = val;
+}
+
+/*
+ * this is some deeply nasty code.
+ *
+ * The end result is that anyone who #includes ctree.h gets a
+ * declaration for the btrfs_set_foo functions and btrfs_foo functions,
+ * which are wrappers of btrfs_set_token_#bits functions and
+ * btrfs_get_token_#bits functions, which are defined in this file.
+ *
+ * These setget functions do all the extent_buffer related mapping
+ * required to efficiently read and write specific fields in the extent
+ * buffers. Every pointer to metadata items in btrfs is really just
+ * an unsigned long offset into the extent buffer which has been
+ * cast to a specific type. This gives us all the gcc type checking.
+ *
+ * The extent buffer api is used to do the page spanning work required to
+ * have a metadata blocksize different from the page size.
+ */
+
+#define DEFINE_BTRFS_SETGET_BITS(bits) \
+u##bits btrfs_get_token_##bits(const struct extent_buffer *eb, \
+ const void *ptr, unsigned long off, \
+ struct btrfs_map_token *token) \
+{ \
+ unsigned long part_offset = (unsigned long)ptr; \
+ unsigned long offset = part_offset + off; \
+ void *p; \
+ int err; \
+ char *kaddr; \
+ unsigned long map_start; \
+ unsigned long map_len; \
+ int size = sizeof(u##bits); \
+ u##bits res; \
+ \
+ if (token && token->kaddr && token->offset <= offset && \
+ token->eb == eb && \
+ (token->offset + PAGE_SIZE >= offset + size)) { \
+ kaddr = token->kaddr; \
+ p = kaddr + part_offset - token->offset; \
+ res = get_unaligned_le##bits(p + off); \
+ return res; \
+ } \
+ err = map_private_extent_buffer(eb, offset, size, \
+ &kaddr, &map_start, &map_len); \
+ if (err) { \
+ __le##bits leres; \
+ \
+ read_extent_buffer(eb, &leres, offset, size); \
+ return le##bits##_to_cpu(leres); \
+ } \
+ p = kaddr + part_offset - map_start; \
+ res = get_unaligned_le##bits(p + off); \
+ if (token) { \
+ token->kaddr = kaddr; \
+ token->offset = map_start; \
+ token->eb = eb; \
+ } \
+ return res; \
+} \
+void btrfs_set_token_##bits(struct extent_buffer *eb, \
+ const void *ptr, unsigned long off, \
+ u##bits val, \
+ struct btrfs_map_token *token) \
+{ \
+ unsigned long part_offset = (unsigned long)ptr; \
+ unsigned long offset = part_offset + off; \
+ void *p; \
+ int err; \
+ char *kaddr; \
+ unsigned long map_start; \
+ unsigned long map_len; \
+ int size = sizeof(u##bits); \
+ \
+ if (token && token->kaddr && token->offset <= offset && \
+ token->eb == eb && \
+ (token->offset + PAGE_SIZE >= offset + size)) { \
+ kaddr = token->kaddr; \
+ p = kaddr + part_offset - token->offset; \
+ put_unaligned_le##bits(val, p + off); \
+ return; \
+ } \
+ err = map_private_extent_buffer(eb, offset, size, \
+ &kaddr, &map_start, &map_len); \
+ if (err) { \
+ __le##bits val2; \
+ \
+ val2 = cpu_to_le##bits(val); \
+ write_extent_buffer(eb, &val2, offset, size); \
+ return; \
+ } \
+ p = kaddr + part_offset - map_start; \
+ put_unaligned_le##bits(val, p + off); \
+ if (token) { \
+ token->kaddr = kaddr; \
+ token->offset = map_start; \
+ token->eb = eb; \
+ } \
+}
+
+DEFINE_BTRFS_SETGET_BITS(8)
+DEFINE_BTRFS_SETGET_BITS(16)
+DEFINE_BTRFS_SETGET_BITS(32)
+DEFINE_BTRFS_SETGET_BITS(64)
+
+void btrfs_node_key(const struct extent_buffer *eb,
+ struct btrfs_disk_key *disk_key, int nr)
+{
+ unsigned long ptr = btrfs_node_key_ptr_offset(nr);
+ read_eb_member(eb, (struct btrfs_key_ptr *)ptr,
+ struct btrfs_key_ptr, key, disk_key);
+}