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 | 13 +++++++++++++
 io_uring/rsrc.c              | 35 +++++++++++++++++++++++++++++++++++
 2 files changed, 48 insertions(+)

diff --git a/include/linux/io_uring/cmd.h b/include/linux/io_uring/cmd.h
index bbf57da1e4c8..42801f0b6456 100644
--- a/include/linux/io_uring/cmd.h
+++ b/include/linux/io_uring/cmd.h
@@ -94,6 +94,10 @@ bool io_uring_mshot_cmd_post_cqe(struct io_uring_cmd *ioucmd,
 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, void (*release)(void *),
+			    void *priv, 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
@@ -146,6 +150,15 @@ 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,
+					  void (*release)(void *), void *priv,
+					  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 5384fbbf684e..4aada6548ac5 100644
--- a/io_uring/rsrc.c
+++ b/io_uring/rsrc.c
@@ -1006,6 +1006,41 @@ int io_buffer_register_request(struct io_uring_cmd *cmd, struct request *rq,
 }
 EXPORT_SYMBOL_GPL(io_buffer_register_request);
 
+/*
+ * bvs is copied internally. caller may free it on return.
+ */
+int io_buffer_register_bvec(struct io_uring_cmd *cmd, const struct bio_vec *bvs,
+			    unsigned int nr_bvecs, void (*release)(void *),
+			    void *priv, 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, total_bytes = 0;
+	int ret = 0;
+
+	for (i = 0; i < nr_bvecs; i++)
+		total_bytes += bvs[i].bv_len;
+
+	io_ring_submit_lock(ctx, issue_flags);
+	imu = io_kernel_buffer_init(ctx, nr_bvecs, total_bytes, dir, release,
+				    priv, index);
+	if (IS_ERR(imu)) {
+		ret = PTR_ERR(imu);
+		goto unlock;
+	}
+
+	bvec = imu->bvec;
+	for (i = 0; i < nr_bvecs; i++)
+		bvec[i] = bvs[i];
+
+unlock:
+	io_ring_submit_unlock(ctx, issue_flags);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(io_buffer_register_bvec);
+
 int io_buffer_unregister(struct io_uring_cmd *cmd, unsigned int index,
 			 unsigned int issue_flags)
 {
-- 
2.52.0