1 files changed, 47 insertions, 12 deletions

diff --git a/fs/bcachefs/thread_with_file.h b/fs/bcachefs/thread_with_file.h
index 05879c5048c8..af54ea8f5b0f 100644
--- a/fs/bcachefs/thread_with_file.h
+++ b/fs/bcachefs/thread_with_file.h
@@ -4,6 +4,38 @@
 
 #include "thread_with_file_types.h"
 
+/*
+ * Thread with file: Run a kthread and connect it to a file descriptor, so that
+ * it can be interacted with via fd read/write methods and closing the file
+ * descriptor stops the kthread.
+ *
+ * We have two different APIs:
+ *
+ * thread_with_file, the low level version.
+ * You get to define the full file_operations, including your release function,
+ * which means that you must call bch2_thread_with_file_exit() from your
+ * .release method
+ *
+ * thread_with_stdio, the higher level version
+ * This implements full piping of input and output, including .poll.
+ *
+ * Notes on behaviour:
+ *  - kthread shutdown behaves like writing or reading from a pipe that has been
+ *    closed
+ *  - Input and output buffers are 4096 bytes, although buffers may in some
+ *    situations slightly exceed that limit so as to avoid chopping off a
+ *    message in the middle in nonblocking mode.
+ *  - Input/output buffers are lazily allocated, with GFP_NOWAIT allocations -
+ *    should be fine but might change in future revisions.
+ *  - Output buffer may grow past 4096 bytes to deal with messages that are
+ *    bigger than 4096 bytes
+ *  - Writing may be done blocking or nonblocking; in nonblocking mode, we only
+ *    drop entire messages.
+ *
+ * To write, use stdio_redirect_printf()
+ * To read, use stdio_redirect_read() or stdio_redirect_readline()
+ */
+
 struct task_struct;
 
 struct thread_with_file {
@@ -17,25 +49,28 @@ int bch2_run_thread_with_file(struct thread_with_file *,
 			      const struct file_operations *,
 			      int (*fn)(void *));
 
+struct thread_with_stdio;
+
+struct thread_with_stdio_ops {
+	void (*exit)(struct thread_with_stdio *);
+	int (*fn)(struct thread_with_stdio *);
+	long (*unlocked_ioctl)(struct thread_with_stdio *, unsigned int, unsigned long);
+};
+
 struct thread_with_stdio {
 	struct thread_with_file	thr;
 	struct stdio_redirect	stdio;
-	DARRAY(char)		output2;
-	void			(*exit)(struct thread_with_stdio *);
+	const struct thread_with_stdio_ops	*ops;
 };
 
-static inline void thread_with_stdio_done(struct thread_with_stdio *thr)
-{
-	thr->thr.done = true;
-	thr->stdio.done = true;
-	wake_up(&thr->stdio.input_wait);
-	wake_up(&thr->stdio.output_wait);
-}
-
 int bch2_run_thread_with_stdio(struct thread_with_stdio *,
-			       void (*exit)(struct thread_with_stdio *),
-			       int (*fn)(void *));
+			       const struct thread_with_stdio_ops *);
+int bch2_run_thread_with_stdout(struct thread_with_stdio *,
+				const struct thread_with_stdio_ops *);
 int bch2_stdio_redirect_read(struct stdio_redirect *, char *, size_t);
 int bch2_stdio_redirect_readline(struct stdio_redirect *, char *, size_t);
 
+__printf(3, 0) ssize_t bch2_stdio_redirect_vprintf(struct stdio_redirect *, bool, const char *, va_list);
+__printf(3, 4) ssize_t bch2_stdio_redirect_printf(struct stdio_redirect *, bool, const char *, ...);
+
 #endif /* _BCACHEFS_THREAD_WITH_FILE_H */