Re: [PATCHSET v2] io_uring: support fileset add/remove/modify

[Jeff Moyer <jmoyer@redhat.com>]

Jens Axboe <axboe@kernel.dk> writes:

> Currently we only support registrering a fixed file set. If changes need
> to be made to that set, the application must unregister the existing set
> first, then register a new one.
>
> This patchset adds support for sparse file sets (patch 1), which means
> the application can register a fileset with room for expansion. This is
> done through having unregistered slots use fd == -1.
>
> On top of that, we can add IORING_REGISTER_FILES_UPDATE. This allows
> modifying the existing file set through:
>
> - Replacing empty slots with valid file descriptors
> - Replacing valid descriptors with an empty slot
> - Modifying an existing slot, replacing a file descriptor with a new one

I don't pretend to understand the socket code you wrote.  The io_uring
bits look good to me.  I also added a testcase to your file-register.c
program--diff below.  The test passes, of course.  :)

Reviewed-by: Jeff Moyer <jmoyer@redhat.com>

Cheers,
Jeff

diff --git a/test/file-register.c b/test/file-register.c
index b25f0f5..322545f 100644
--- a/test/file-register.c
+++ b/test/file-register.c
@@ -358,6 +358,40 @@ err:
 	return 1;
 }
 
+/*
+ * Register 0 files, but reserve space for 10.  Then add one file.
+ */
+static int test_zero(struct io_uring *ring)
+{
+	struct io_uring_files_update up;
+	int *files;
+	int ret;
+
+	files = open_files(0, 10, 0);
+	ret = io_uring_register(ring->ring_fd, IORING_REGISTER_FILES, files, 10);
+	if (ret)
+		goto err;
+
+	up.fds = open_files(1, 0, 1);
+	up.offset = 0;
+	ret = io_uring_register(ring->ring_fd,
+				IORING_REGISTER_FILES_UPDATE, &up, 1);
+	if (ret != 1) {
+		printf("ret=%d, errno=%d\n", ret, errno);
+		goto err;
+	}
+
+	ret = io_uring_register(ring->ring_fd, IORING_UNREGISTER_FILES, NULL, 0);
+	if (ret)
+		goto err;
+
+	close_files(up.fds, 1, 1);
+	return 0;
+err:
+	close_files(up.fds, 1, 1);
+	return 1;
+}
+
 int main(int argc, char *argv[])
 {
 	struct io_uring ring;
@@ -426,5 +460,11 @@ int main(int argc, char *argv[])
 		return ret;
 	}
 
+	ret = test_zero(&ring);
+	if (ret) {
+		printf("test_zero failed\n");
+		return ret;
+	}
+
 	return 0;
 }