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SubjectRe: [PATCH v2 1/2] net/9p: embed fcall in req to round down buffer allocs
On Thu,  2 Aug 2018 04:37:31 +0200
Dominique Martinet <asmadeus@codewreck.org> wrote:

> From: Dominique Martinet <dominique.martinet@cea.fr>
>
> 'msize' is often a power of two, or at least page-aligned, so avoiding
> an overhead of two dozen bytes for each allocation will help the
> allocator do its work and reduce memory fragmentation.
>
> Suggested-by: Matthew Wilcox <willy@infradead.org>
> Signed-off-by: Dominique Martinet <dominique.martinet@cea.fr>
> Cc: Matthew Wilcox <willy@infradead.org>
> Cc: Greg Kurz <groug@kaod.org>
> Cc: Jun Piao <piaojun@huawei.com>
> ---
>
> v2:
> - Add extra label to not free uninitialized memory on alloc failure
> - Rename p9_fcall_alloc to 9p_fcall_init
> - Add a p9_fcall_fini function to echo to init
>
[...]
> diff --git a/net/9p/trans_rdma.c b/net/9p/trans_rdma.c
> index 2ab4574183c9..c5cac97df7f7 100644
> --- a/net/9p/trans_rdma.c
> +++ b/net/9p/trans_rdma.c
> @@ -122,7 +122,7 @@ struct p9_rdma_context {
> dma_addr_t busa;
> union {
> struct p9_req_t *req;
> - struct p9_fcall *rc;
> + struct p9_fcall rc;
> };
> };
>
> @@ -320,8 +320,8 @@ recv_done(struct ib_cq *cq, struct ib_wc *wc)
> if (wc->status != IB_WC_SUCCESS)
> goto err_out;
>
> - c->rc->size = wc->byte_len;
> - err = p9_parse_header(c->rc, NULL, NULL, &tag, 1);
> + c->rc.size = wc->byte_len;
> + err = p9_parse_header(&c->rc, NULL, NULL, &tag, 1);
> if (err)
> goto err_out;
>
> @@ -331,12 +331,13 @@ recv_done(struct ib_cq *cq, struct ib_wc *wc)
>
> /* Check that we have not yet received a reply for this request.
> */
> - if (unlikely(req->rc)) {
> + if (unlikely(req->rc.sdata)) {
> pr_err("Duplicate reply for request %d", tag);
> goto err_out;
> }
>
> - req->rc = c->rc;
> + req->rc.size = c->rc.size;
> + req->rc.sdata = c->rc.sdata;
> p9_client_cb(client, req, REQ_STATUS_RCVD);
>
> out:
> @@ -361,7 +362,7 @@ send_done(struct ib_cq *cq, struct ib_wc *wc)
> container_of(wc->wr_cqe, struct p9_rdma_context, cqe);
>
> ib_dma_unmap_single(rdma->cm_id->device,
> - c->busa, c->req->tc->size,
> + c->busa, c->req->tc.size,
> DMA_TO_DEVICE);
> up(&rdma->sq_sem);
> kfree(c);
> @@ -401,7 +402,7 @@ post_recv(struct p9_client *client, struct p9_rdma_context *c)
> struct ib_sge sge;
>
> c->busa = ib_dma_map_single(rdma->cm_id->device,
> - c->rc->sdata, client->msize,
> + c->rc.sdata, client->msize,
> DMA_FROM_DEVICE);
> if (ib_dma_mapping_error(rdma->cm_id->device, c->busa))
> goto error;
> @@ -443,9 +444,9 @@ static int rdma_request(struct p9_client *client, struct p9_req_t *req)
> **/
> if (unlikely(atomic_read(&rdma->excess_rc) > 0)) {
> if ((atomic_sub_return(1, &rdma->excess_rc) >= 0)) {
> - /* Got one ! */
> - kfree(req->rc);
> - req->rc = NULL;
> + /* Got one! */
> + kfree(req->rc.sdata);

Shouldn't this be p9_fcall_fini(&req->rc) ?

The rest looks good, so, with that fixed, you can add:

Reviewed-by: Greg Kurz <groug@kaod.org>

> + req->rc.sdata = NULL;
> goto dont_need_post_recv;
> } else {
> /* We raced and lost. */

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