[PATCH v2] io_uring: let IORING_OP_FILES_UPDATE support to choose fixed file slots

Xiaoguang Wang
2022-05-30T13:15:31Z

One big issue with file registration feature is that it needs user
space apps to maintain free slot info about io_uring's fixed file
table, which really is a burden for development. Now since io_uring
starts to choose free file slot for user space apps by using
IORING_FILE_INDEX_ALLOC flag in accept or open operations, but they
need app to uses direct accept or direct open, which as far as I know,
some apps are not prepared to use direct accept or open yet.

To support apps, who still need real fds, use registration feature
easier, let IORING_OP_FILES_UPDATE support to choose fixed file slots,
which will store picked fixed files slots in fd array and let cqe return
the number of slots allocated.

Suggested-by: Hao Xu <howeyxu@tencent.com>
Signed-off-by: Xiaoguang Wang <xiaoguang.wang@linux.alibaba.com>
---
V2:
Add illegal flags check in io_close_prep().
---
fs/io_uring.c | 75 +++++++++++++++++++++++++++++++++++++------
include/uapi/linux/io_uring.h | 1 +
2 files changed, 66 insertions(+), 10 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 6d91148e9679..18a7459fb6e7 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -574,6 +574,7 @@ struct io_close {
struct file *file;
int fd;
u32 file_slot;
+ u32 flags;
};

struct io_timeout_data {
@@ -1366,7 +1367,9 @@ static int io_req_prep_async(struct io_kiocb *req);

static int io_install_fixed_file(struct io_kiocb *req, struct file *file,
unsigned int issue_flags, u32 slot_index);
-static int io_close_fixed(struct io_kiocb *req, unsigned int issue_flags);
+static int __io_close_fixed(struct io_kiocb *req, unsigned int issue_flags,
+ unsigned int offset);
+static inline int io_close_fixed(struct io_kiocb *req, unsigned int issue_flags);

static enum hrtimer_restart io_link_timeout_fn(struct hrtimer *timer);
static void io_eventfd_signal(struct io_ring_ctx *ctx);
@@ -5945,16 +5948,22 @@ static int io_statx(struct io_kiocb *req, unsigned int issue_flags)
return 0;
}

+#define IORING_CLOSE_FD_AND_FILE_SLOT 1
+
static int io_close_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
{
- if (sqe->off || sqe->addr || sqe->len || sqe->rw_flags || sqe->buf_index)
+ if (sqe->off || sqe->addr || sqe->len || sqe->buf_index)
return -EINVAL;
if (req->flags & REQ_F_FIXED_FILE)
return -EBADF;

req->close.fd = READ_ONCE(sqe->fd);
req->close.file_slot = READ_ONCE(sqe->file_index);
- if (req->close.file_slot && req->close.fd)
+ req->close.flags = READ_ONCE(sqe->close_flags);
+ if (req->close.flags & ~IORING_CLOSE_FD_AND_FILE_SLOT)
+ return -EINVAL;
+ if (!(req->close.flags & IORING_CLOSE_FD_AND_FILE_SLOT) &&
+ req->close.file_slot && req->close.fd)
return -EINVAL;

return 0;
@@ -5970,7 +5979,8 @@ static int io_close(struct io_kiocb *req, unsigned int issue_flags)

if (req->close.file_slot) {
ret = io_close_fixed(req, issue_flags);
- goto err;
+ if (ret || !(req->close.flags & IORING_CLOSE_FD_AND_FILE_SLOT))
+ goto err;
}

spin_lock(&files->file_lock);
@@ -8003,6 +8013,42 @@ static int io_files_update_prep(struct io_kiocb *req,
return 0;
}

+static int io_files_update_with_index_alloc(struct io_kiocb *req,
+ unsigned int issue_flags)
+{
+ __s32 __user *fds = u64_to_user_ptr(req->rsrc_update.arg);
+ struct file *file;
+ unsigned int done, nr_fds = req->rsrc_update.nr_args;
+ int ret, fd;
+
+ for (done = 0; done < nr_fds; done++) {
+ if (copy_from_user(&fd, &fds[done], sizeof(fd))) {
+ ret = -EFAULT;
+ break;
+ }
+
+ file = fget(fd);
+ if (!file) {
+ ret = -EBADF;
+ goto out;
+ }
+ ret = io_fixed_fd_install(req, issue_flags, file,
+ IORING_FILE_INDEX_ALLOC);
+ if (ret < 0)
+ goto out;
+ if (copy_to_user(&fds[done], &ret, sizeof(ret))) {
+ ret = -EFAULT;
+ __io_close_fixed(req, issue_flags, ret);
+ break;
+ }
+ }
+
+out:
+ if (done)
+ return done;
+ return ret;
+}
+
static int io_files_update(struct io_kiocb *req, unsigned int issue_flags)
{
struct io_ring_ctx *ctx = req->ctx;
@@ -8016,10 +8062,14 @@ static int io_files_update(struct io_kiocb *req, unsigned int issue_flags)
up.resv = 0;
up.resv2 = 0;

- io_ring_submit_lock(ctx, issue_flags);
- ret = __io_register_rsrc_update(ctx, IORING_RSRC_FILE,
- &up, req->rsrc_update.nr_args);
- io_ring_submit_unlock(ctx, issue_flags);
+ if (req->rsrc_update.offset == IORING_FILE_INDEX_ALLOC) {
+ ret = io_files_update_with_index_alloc(req, issue_flags);
+ } else {
+ io_ring_submit_lock(ctx, issue_flags);
+ ret = __io_register_rsrc_update(ctx, IORING_RSRC_FILE,
+ &up, req->rsrc_update.nr_args);
+ io_ring_submit_unlock(ctx, issue_flags);
+ }

if (ret < 0)
req_set_fail(req);
@@ -10183,9 +10233,9 @@ static int io_install_fixed_file(struct io_kiocb *req, struct file *file,
return ret;
}

-static int io_close_fixed(struct io_kiocb *req, unsigned int issue_flags)
+static int __io_close_fixed(struct io_kiocb *req, unsigned int issue_flags,
+ unsigned int offset)
{
- unsigned int offset = req->close.file_slot - 1;
struct io_ring_ctx *ctx = req->ctx;
struct io_fixed_file *file_slot;
struct file *file;
@@ -10222,6 +10272,11 @@ static int io_close_fixed(struct io_kiocb *req, unsigned int issue_flags)
return ret;
}

+static inline int io_close_fixed(struct io_kiocb *req, unsigned int issue_flags)
+{
+ return __io_close_fixed(req, issue_flags, req->close.file_slot - 1);
+}
+
static int __io_sqe_files_update(struct io_ring_ctx *ctx,
struct io_uring_rsrc_update2 *up,
unsigned nr_args)
diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h
index 53e7dae92e42..e347b3fea4e4 100644
--- a/include/uapi/linux/io_uring.h
+++ b/include/uapi/linux/io_uring.h
@@ -47,6 +47,7 @@ struct io_uring_sqe {
__u32 unlink_flags;
__u32 hardlink_flags;
__u32 xattr_flags;
+ __u32 close_flags;
};
__u64 user_data; /* data to be passed back at completion time */
/* pack this to avoid bogus arm OABI complaints */
--
2.14.4.44.g2045bb6