From: Kent Overstreet <[email protected]>
Signed-off-by: Kent Overstreet <[email protected]>
Reviewed-by: Darrick J. Wong <[email protected]>
Signed-off-by: Darrick J. Wong <[email protected]>
---
fs/bcachefs/thread_with_file.c | 15 ++++++++-------
fs/bcachefs/thread_with_file.h | 32 ++++++++++++++++++++++++++++++++
2 files changed, 40 insertions(+), 7 deletions(-)
diff --git a/fs/bcachefs/thread_with_file.c b/fs/bcachefs/thread_with_file.c
index 830efb06ef0be..dde9679b68b42 100644
--- a/fs/bcachefs/thread_with_file.c
+++ b/fs/bcachefs/thread_with_file.c
@@ -76,16 +76,16 @@ static bool stdio_redirect_has_output(struct stdio_redirect
*stdio)
return stdio->output.buf.nr || stdio->done;
}
-#define WRITE_BUFFER 4096
+#define STDIO_REDIRECT_BUFSIZE 4096
static bool stdio_redirect_has_input_space(struct stdio_redirect *stdio)
{
- return stdio->input.buf.nr < WRITE_BUFFER || stdio->done;
+ return stdio->input.buf.nr < STDIO_REDIRECT_BUFSIZE || stdio->done;
}
static bool stdio_redirect_has_output_space(struct stdio_redirect *stdio)
{
- return stdio->output.buf.nr < WRITE_BUFFER || stdio->done;
+ return stdio->output.buf.nr < STDIO_REDIRECT_BUFSIZE || stdio->done;
}
static void stdio_buf_init(struct stdio_buf *buf)
@@ -171,11 +171,12 @@ static ssize_t thread_with_stdio_write(struct file *file,
const char __user *ubu
}
spin_lock(&buf->lock);
- if (buf->buf.nr < WRITE_BUFFER)
- darray_make_room_gfp(&buf->buf, min(b, WRITE_BUFFER -
buf->buf.nr), __GFP_NOWARN);
+ if (buf->buf.nr < STDIO_REDIRECT_BUFSIZE)
+ darray_make_room_gfp(&buf->buf,
+ min(b, STDIO_REDIRECT_BUFSIZE - buf->buf.nr),
GFP_NOWAIT);
b = min(len, darray_room(buf->buf));
- if (b && !copy_from_user_nofault(&buf->buf.data[buf->buf.nr],
ubuf, b)) {
+ if (b && !copy_from_user_nofault(&darray_top(buf->buf), ubuf,
b)) {
buf->buf.nr += b;
ubuf += b;
len -= b;
@@ -338,7 +339,7 @@ void bch2_stdio_redirect_vprintf(struct stdio_redirect
*stdio, bool nonblocking,
return;
spin_lock_irqsave(&buf->lock, flags);
- bch2_darray_vprintf(&buf->buf, nonblocking ? __GFP_NOWARN : GFP_KERNEL,
fmt, args);
+ bch2_darray_vprintf(&buf->buf, nonblocking ? GFP_NOWAIT : GFP_KERNEL,
fmt, args);
spin_unlock_irqrestore(&buf->lock, flags);
wake_up(&buf->wait);
diff --git a/fs/bcachefs/thread_with_file.h b/fs/bcachefs/thread_with_file.h
index 66212fcae226a..f06f8ff19a790 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 {
