Re: [PATCH v2 05/16] splice: remove permission hook from iter_file_splice_write()

[Christoph Hellwig <hch@infradead.org>]

On Thu, Nov 23, 2023 at 01:20:13PM +0200, Amir Goldstein wrote:
> >  - first obviously the name, based on the other functions it probably
> >    should be in the __kernel_* namespace unless I'm missing something.
> 
> Not sure about the best name.
> I just derived the name from do_iter_readv_writev(), which would be the
> name of this helper if we split up do_iter_readv_writev() as you suggested.

Well, I don't think do_iter_readv_writev is a particular good name
even now, but certainly not once it is more than just a static helper
with two callers.

I can't say __kernel is an all that great name either, but it seems
to match the existing ones. 

That being said - it just is a tiny wrapper anyway, what about just
open coding it instead of bike shedding?  See below for a patch,
this actually seems pretty reasonable and very readable.

---
diff --git a/fs/splice.c b/fs/splice.c
index d983d375ff1130..982a0872fa03e9 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -684,6 +684,7 @@ iter_file_splice_write(struct pipe_inode_info *pipe, struct file *out,
 
 	splice_from_pipe_begin(&sd);
 	while (sd.total_len) {
+		struct kiocb kiocb;
 		struct iov_iter from;
 		unsigned int head, tail, mask;
 		size_t left;
@@ -733,7 +734,10 @@ iter_file_splice_write(struct pipe_inode_info *pipe, struct file *out,
 		}
 
 		iov_iter_bvec(&from, ITER_SOURCE, array, n, sd.total_len - left);
-		ret = vfs_iter_write(out, &from, &sd.pos, 0);
+		init_sync_kiocb(&kiocb, out);
+		kiocb.ki_pos = sd.pos;
+		ret = out->f_op->write_iter(&kiocb, &from);
+		sd.pos = kiocb.ki_pos;
 		if (ret <= 0)
 			break;