libmount: consolidate btrfs stuff, make it more portable

- add --with-btrfs (enabled by default)
- check for linux/btrfs.h
- add "btrfs" to libmount features list (see mount -V)
- #ifdef HAVE_BTRFS_SUPPORT for all btrfs stuff in libmount

Signed-off-by: Karel Zak <kzak@redhat.com>

1 files changed, 81 insertions, 9 deletions

diff --git a/libmount/src/btrfs.c b/libmount/src/btrfs.c
index 3c61a2a03..1db604a87 100644
--- a/libmount/src/btrfs.c
+++ b/libmount/src/btrfs.c
@@ -1,4 +1,5 @@
 /*
+ * Copyright (C) 1999 Andrea Arcangeli <andrea@suse.de>
  * Copyright (C) 2016 David Sterba <dsterba@suse.cz>
  * Copyright (C) 2016 Stanislav Brabec <sbrabec@suse.cz>
  *
@@ -6,17 +7,89 @@
  * GNU Lesser General Public License.
  */
 
+#include <dirent.h>
+#include <sys/ioctl.h>
+#include <libio.h>
+#include <stdint.h>
+#include <linux/btrfs.h>
+
+#include "mountP.h"
+#include "bitops.h"
+
+
+/* linux/btrfs.h lacks large parts of stuff needed for getting default
+ * sub-volume. Suppose that if BTRFS_DIR_ITEM_KEY is not defined, all
+ * declarations are still missing.
+ */
+#ifndef BTRFS_DIR_ITEM_KEY
+
+/*
+ * dir items are the name -> inode pointers in a directory.  There is one
+ * for every name in a directory.
+ */
+#define BTRFS_DIR_ITEM_KEY	84
+
+/* holds pointers to all of the tree roots */
+#define BTRFS_ROOT_TREE_OBJECTID 1ULL
+
+/* directory objectid inside the root tree */
+#define BTRFS_ROOT_TREE_DIR_OBJECTID 6ULL
+
 /*
- * SECTION: btrfs
- * @title: btrfs
- * @short_description: special function for btrfs
+ * the key defines the order in the tree, and so it also defines (optimal)
+ * block layout.  objectid corresonds to the inode number.  The flags
+ * tells us things about the object, and is a kind of stream selector.
+ * so for a given inode, keys with flags of 1 might refer to the inode
+ * data, flags of 2 may point to file data in the btree and flags == 3
+ * may point to extents.
  *
- * btrfs contains function needed for manipulation with btrfs.
+ * offset is the starting byte offset for this key in the stream.
+ *
+ * btrfs_disk_key is in disk byte order.  struct btrfs_key is always
+ * in cpu native order.  Otherwise they are identical and their sizes
+ * should be the same (ie both packed)
  */
-#include <dirent.h>
-#include <sys/ioctl.h>
-#include <linux/magic.h>
-#include "btrfs.h"
+struct btrfs_disk_key {
+	uint64_t objectid; /* little endian */
+	uint8_t type;
+	uint64_t offset; /* little endian */
+} __attribute__ ((__packed__));
+
+struct btrfs_dir_item {
+	struct btrfs_disk_key location;
+	uint64_t transid; /* little endian */
+	uint16_t data_len; /* little endian */
+	uint16_t name_len; /* little endian */
+	uint8_t type;
+} __attribute__ ((__packed__));
+
+#define BTRFS_SETGET_STACK_FUNCS(name, type, member, bits)		\
+static inline uint##bits##_t btrfs_##name(const type *s)		\
+{									\
+	return le##bits##_to_cpu(s->member);				\
+}									\
+static inline void btrfs_set_##name(type *s, uint##bits##_t val)	\
+{									\
+	s->member = cpu_to_le##bits(val);				\
+}
+
+/* struct btrfs_disk_key */
+BTRFS_SETGET_STACK_FUNCS(disk_key_objectid, struct btrfs_disk_key,
+			 objectid, 64);
+
+BTRFS_SETGET_STACK_FUNCS(stack_dir_name_len, struct btrfs_dir_item, name_len, 16);
+
+/*
+  Red Black Trees
+*/
+struct rb_node {
+	unsigned long  __rb_parent_color;
+	struct rb_node *rb_right;
+	struct rb_node *rb_left;
+} __attribute__((aligned(sizeof(long))));
+    /* The alignment might seem pointless, but allegedly CRIS needs it */
+
+#endif /* BTRFS_DIR_ITEM_KEY */
 
 /*
  * btrfs_get_default_subvol_id:
@@ -97,6 +170,5 @@ uint64_t btrfs_get_default_subvol_id(const char *path)
 
 out:
 	closedir(dirstream);
-
 	return found;
 }