io_uring: follow **iovec idiom in io_import_iovec

As for import_iovec(), return !=NULL iovec from io_import_iovec() only
when it should be freed. That includes returning NULL when iovec is
already in req->io, because it should be deallocated by other means,
e.g. inside op handler. After io_setup_async_rw() local iovec to ->io,
just mark it NULL, to follow the idea in io_{read,write} as well.

That's easier to follow, and especially useful if we want to reuse
per-op space for completion data.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
[axboe: only call kfree() on non-NULL pointer]
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 31466bc..64ae5b6 100644 (file)
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -2740,10 +2740,8 @@ static ssize_t io_import_iovec(int rw, struct io_kiocb *req,
        if (req->io) {
                struct io_async_rw *iorw = &req->io->rw;
 
-               *iovec = iorw->iov;
-               iov_iter_init(iter, rw, *iovec, iorw->nr_segs, iorw->size);
-               if (iorw->iov == iorw->fast_iov)
-                       *iovec = NULL;
+               iov_iter_init(iter, rw, iorw->iov, iorw->nr_segs, iorw->size);
+               *iovec = NULL;
                return iorw->size;
        }
 
@@ -3026,6 +3024,8 @@ copy_iov:
                                                inline_vecs, &iter);
                        if (ret)
                                goto out_free;
+                       /* it's copied and will be cleaned with ->io */
+                       iovec = NULL;
                        /* if we can retry, do so with the callbacks armed */
                        if (io_rw_should_retry(req)) {
                                ret2 = io_iter_do_read(req, &iter);
@@ -3041,7 +3041,7 @@ copy_iov:
                }
        }
 out_free:
-       if (!(req->flags & REQ_F_NEED_CLEANUP))
+       if (iovec)
                kfree(iovec);
        return ret;
 }
@@ -3143,11 +3143,13 @@ copy_iov:
                                                inline_vecs, &iter);
                        if (ret)
                                goto out_free;
+                       /* it's copied and will be cleaned with ->io */
+                       iovec = NULL;
                        return -EAGAIN;
                }
        }
 out_free:
-       if (!(req->flags & REQ_F_NEED_CLEANUP))
+       if (iovec)
                kfree(iovec);
        return ret;
 }