move Rust sources to top level, C sources into c_src

This moves the Rust sources out of rust_src/ and into the top level.
Running the bcachefs executable out of the development tree is now:

$ ./target/release/bcachefs command
or
$ cargo run --profile release -- command

instead of "./bcachefs command".

Building and installing is still:

$ make && make install

Signed-off-by: Thomas Bertschinger <tahbertschinger@gmail.com>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

1 files changed, 68 insertions, 0 deletions

diff --git a/c_src/include/linux/err.h b/c_src/include/linux/err.h
new file mode 100644
index 00000000..e94bdff5
--- /dev/null
+++ b/c_src/include/linux/err.h
@@ -0,0 +1,68 @@
+#ifndef __TOOLS_LINUX_ERR_H
+#define __TOOLS_LINUX_ERR_H
+
+#include <linux/compiler.h>
+#include <linux/types.h>
+
+#include <asm/errno.h>
+
+/*
+ * Original kernel header comment:
+ *
+ * Kernel pointers have redundant information, so we can use a
+ * scheme where we can return either an error code or a normal
+ * pointer with the same return value.
+ *
+ * This should be a per-architecture thing, to allow different
+ * error and pointer decisions.
+ *
+ * Userspace note:
+ * The same principle works for userspace, because 'error' pointers
+ * fall down to the unused hole far from user space, as described
+ * in Documentation/x86/x86_64/mm.txt for x86_64 arch:
+ *
+ * 0000000000000000 - 00007fffffffffff (=47 bits) user space, different per mm hole caused by [48:63] sign extension
+ * ffffffffffe00000 - ffffffffffffffff (=2 MB) unused hole
+ *
+ * It should be the same case for other architectures, because
+ * this code is used in generic kernel code.
+ */
+#define MAX_ERRNO	4095
+
+#define IS_ERR_VALUE(x) unlikely((x) >= (unsigned long)-MAX_ERRNO)
+
+static inline void * __must_check ERR_PTR(long error_)
+{
+	return (void *) error_;
+}
+
+static inline long __must_check PTR_ERR(__force const void *ptr)
+{
+	return (long) ptr;
+}
+
+static inline bool __must_check IS_ERR(__force const void *ptr)
+{
+	return IS_ERR_VALUE((unsigned long)ptr);
+}
+
+static inline bool __must_check IS_ERR_OR_NULL(__force const void *ptr)
+{
+	return unlikely(!ptr) || IS_ERR_VALUE((unsigned long)ptr);
+}
+
+static inline void * __must_check ERR_CAST(__force const void *ptr)
+{
+	/* cast away the const */
+	return (void *) ptr;
+}
+
+static inline int __must_check PTR_ERR_OR_ZERO(__force const void *ptr)
+{
+	if (IS_ERR(ptr))
+		return PTR_ERR(ptr);
+	else
+		return 0;
+}
+
+#endif /* _LINUX_ERR_H */