[PATCH v4 23/25] io_uring/rsrc: add io_buffer_register_bvec()

[Joanne Koong <joannelkoong@gmail.com>]

Add io_buffer_register_bvec() for registering a bvec array.

This is a preparatory patch for fuse-over-io-uring zero-copy.

Signed-off-by: Joanne Koong <joannelkoong@gmail.com>
Reviewed-by: Caleb Sander Mateos <csander@purestorage.com>
---
 include/linux/io_uring/cmd.h | 12 ++++++++++++
 io_uring/rsrc.c              | 31 +++++++++++++++++++++++++++++++
 2 files changed, 43 insertions(+)

diff --git a/include/linux/io_uring/cmd.h b/include/linux/io_uring/cmd.h
index 73f8ff9317d7..7dde6e2af05b 100644
--- a/include/linux/io_uring/cmd.h
+++ b/include/linux/io_uring/cmd.h
@@ -107,6 +107,9 @@ bool io_uring_is_kmbuf_ring(struct io_uring_cmd *cmd, unsigned int buf_group,
 int io_buffer_register_request(struct io_uring_cmd *cmd, struct request *rq,
 			       void (*release)(void *), unsigned int index,
 			       unsigned int issue_flags);
+int io_buffer_register_bvec(struct io_uring_cmd *cmd, const struct bio_vec *bvs,
+			    unsigned int nr_bvecs, unsigned int total_bytes,
+			    u8 dir, unsigned int index, unsigned int issue_flags);
 int io_buffer_unregister(struct io_uring_cmd *cmd, unsigned int index,
 			 unsigned int issue_flags);
 #else
@@ -197,6 +200,15 @@ static inline int io_buffer_register_request(struct io_uring_cmd *cmd,
 {
 	return -EOPNOTSUPP;
 }
+static inline int io_buffer_register_bvec(struct io_uring_cmd *cmd,
+					  const struct bio_vec *bvs,
+					  unsigned int nr_bvecs,
+					  unsigned int total_bytes, u8 dir,
+					  unsigned int index,
+					  unsigned int issue_flags)
+{
+	return -EOPNOTSUPP;
+}
 static inline int io_buffer_unregister(struct io_uring_cmd *cmd,
 				       unsigned int index,
 				       unsigned int issue_flags)
diff --git a/io_uring/rsrc.c b/io_uring/rsrc.c
index dc43aab0f019..b6350812255b 100644
--- a/io_uring/rsrc.c
+++ b/io_uring/rsrc.c
@@ -1019,6 +1019,37 @@ int io_buffer_register_request(struct io_uring_cmd *cmd, struct request *rq,
 }
 EXPORT_SYMBOL_GPL(io_buffer_register_request);
 
+/*
+ * This internally makes a copy of the bio_vec array. The memory bvs points to
+ * can be freed as soon as this returns.
+ */
+int io_buffer_register_bvec(struct io_uring_cmd *cmd, const struct bio_vec *bvs,
+			    unsigned int nr_bvecs, unsigned int total_bytes,
+			    u8 dir, unsigned int index,
+			    unsigned int issue_flags)
+{
+	struct io_ring_ctx *ctx = cmd_to_io_kiocb(cmd)->ctx;
+	struct io_mapped_ubuf *imu;
+	struct bio_vec *bvec;
+	unsigned int i;
+
+	io_ring_submit_lock(ctx, issue_flags);
+	imu = io_kernel_buffer_init(ctx, nr_bvecs, total_bytes, dir, NULL,
+				    NULL, index);
+	if (IS_ERR(imu)) {
+		io_ring_submit_unlock(ctx, issue_flags);
+		return PTR_ERR(imu);
+	}
+
+	bvec = imu->bvec;
+	for (i = 0; i < nr_bvecs; i++)
+		bvec[i] = bvs[i];
+
+	io_ring_submit_unlock(ctx, issue_flags);
+	return 0;
+}
+EXPORT_SYMBOL_GPL(io_buffer_register_bvec);
+
 int io_buffer_unregister(struct io_uring_cmd *cmd, unsigned int index,
 			 unsigned int issue_flags)
 {
-- 
2.47.3