On 7/9/20 4:15 AM, Christoph Hellwig wrote:

On Sun, Jul 05, 2020 at 03:00:47PM -0600, Jens Axboe wrote:

quoted

quoted

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 155f3d8..cbde4df 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c

@@ -402,6 +402,8 @@ struct io_rw {
 	struct kiocb			kiocb;
 	u64				addr;
 	u64				len;
+	/* zone-relative offset for append, in sectors */
+	u32			append_offset;
 };

I don't like this very much at all. As it stands, the first cacheline
of io_kiocb is set aside for request-private data. io_rw is already
exactly 64 bytes, which means that you're now growing io_rw beyond
a cacheline and increasing the size of io_kiocb as a whole.

Maybe you can reuse io_rw->len for this, as that is only used on the
submission side of things.

We don't actually need any new field at all.  By the time the write
returned ki_pos contains the offset after the write, and the res
argument to ->ki_complete contains the amount of bytes written, which
allow us to trivially derive the starting position.

Then let's just do that instead of jumping through hoops either
justifying growing io_rw/io_kiocb or turning kiocb into a global
completion thing.

-- 
Jens Axboe