[RFC PATCH v4 4/5] btrfs: ioctl: introduce btrfs_uring_import_iovec()

[Sidong Yang <sidong.yang@furiosa.ai>]

This patch introduces btrfs_uring_import_iovec(). In encoded read/write
with uring cmd, it uses import_iovec without supporting fixed buffer.
btrfs_using_import_iovec() could use fixed buffer if cmd flags has
IORING_URING_CMD_FIXED.

Signed-off-by: Sidong Yang <sidong.yang@furiosa.ai>
---
 fs/btrfs/ioctl.c | 32 ++++++++++++++++++++++++--------
 1 file changed, 24 insertions(+), 8 deletions(-)

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 6c18bad53cd3..a7b52fd99059 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -4802,6 +4802,28 @@ struct btrfs_uring_encoded_data {
 	struct iov_iter iter;
 };
 
+static int btrfs_uring_import_iovec(struct io_uring_cmd *cmd,
+				    unsigned int issue_flags, int rw)
+{
+	struct btrfs_uring_encoded_data *data =
+		io_uring_cmd_get_async_data(cmd)->op_data;
+	int ret;
+
+	if (cmd && (cmd->flags & IORING_URING_CMD_FIXED)) {
+		data->iov = NULL;
+		ret = io_uring_cmd_import_fixed_vec(cmd, data->args.iov,
+						    data->args.iovcnt,
+						    ITER_DEST, issue_flags,
+						    &data->iter);
+	} else {
+		data->iov = data->iovstack;
+		ret = import_iovec(rw, data->args.iov, data->args.iovcnt,
+				   ARRAY_SIZE(data->iovstack), &data->iov,
+				   &data->iter);
+	}
+	return ret;
+}
+
 static int btrfs_uring_encoded_read(struct io_uring_cmd *cmd, unsigned int issue_flags)
 {
 	size_t copy_end_kernel = offsetofend(struct btrfs_ioctl_encoded_io_args, flags);
@@ -4874,10 +4896,7 @@ static int btrfs_uring_encoded_read(struct io_uring_cmd *cmd, unsigned int issue
 			goto out_acct;
 		}
 
-		data->iov = data->iovstack;
-		ret = import_iovec(ITER_DEST, data->args.iov, data->args.iovcnt,
-				   ARRAY_SIZE(data->iovstack), &data->iov,
-				   &data->iter);
+		ret = btrfs_uring_import_iovec(cmd, issue_flags, ITER_DEST);
 		if (ret < 0)
 			goto out_acct;
 
@@ -5022,10 +5041,7 @@ static int btrfs_uring_encoded_write(struct io_uring_cmd *cmd, unsigned int issu
 		if (data->args.len > data->args.unencoded_len - data->args.unencoded_offset)
 			goto out_acct;
 
-		data->iov = data->iovstack;
-		ret = import_iovec(ITER_SOURCE, data->args.iov, data->args.iovcnt,
-				   ARRAY_SIZE(data->iovstack), &data->iov,
-				   &data->iter);
+		ret = btrfs_uring_import_iovec(cmd, issue_flags, ITER_SOURCE);
 		if (ret < 0)
 			goto out_acct;
 
-- 
2.43.0