On Thu, 2022-06-09 at 15:34 -0400, Jeff Layton wrote:
> Add an iov_iter to the unions in ceph_msg_data and ceph_msg_data_cursor.
> Instead of requiring a list of pages or bvecs, we can just use an
> iov_iter directly, and avoid extra allocations.
>
> Note that we do assume that the pages represented by the iter are pinned
> such that they shouldn't incur page faults.
>
> Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx>
> ---
> include/linux/ceph/messenger.h | 5 +++
> include/linux/ceph/osd_client.h | 4 +++
> net/ceph/messenger.c | 64 +++++++++++++++++++++++++++++++++
> net/ceph/osd_client.c | 27 ++++++++++++++
> 4 files changed, 100 insertions(+)
>
> diff --git a/include/linux/ceph/messenger.h b/include/linux/ceph/messenger.h
> index 9fd7255172ad..c259021ca4a8 100644
> --- a/include/linux/ceph/messenger.h
> +++ b/include/linux/ceph/messenger.h
> @@ -123,6 +123,7 @@ enum ceph_msg_data_type {
> CEPH_MSG_DATA_BIO, /* data source/destination is a bio list */
> #endif /* CONFIG_BLOCK */
> CEPH_MSG_DATA_BVECS, /* data source/destination is a bio_vec array */
> + CEPH_MSG_DATA_ITER, /* data source/destination is an iov_iter */
> };
>
> #ifdef CONFIG_BLOCK
> @@ -224,6 +225,7 @@ struct ceph_msg_data {
> bool own_pages;
> };
> struct ceph_pagelist *pagelist;
> + struct iov_iter iter;
> };
> };
>
> @@ -248,6 +250,7 @@ struct ceph_msg_data_cursor {
> struct page *page; /* page from list */
> size_t offset; /* bytes from list */
> };
> + struct iov_iter iov_iter;
> };
> };
>
> @@ -605,6 +608,8 @@ void ceph_msg_data_add_bio(struct ceph_msg *msg, struct ceph_bio_iter *bio_pos,
> #endif /* CONFIG_BLOCK */
> void ceph_msg_data_add_bvecs(struct ceph_msg *msg,
> struct ceph_bvec_iter *bvec_pos);
> +void ceph_msg_data_add_iter(struct ceph_msg *msg,
> + struct iov_iter *iter);
>
> struct ceph_msg *ceph_msg_new2(int type, int front_len, int max_data_items,
> gfp_t flags, bool can_fail);
> diff --git a/include/linux/ceph/osd_client.h b/include/linux/ceph/osd_client.h
> index 6ec3cb2ac457..ef0ad534b6c5 100644
> --- a/include/linux/ceph/osd_client.h
> +++ b/include/linux/ceph/osd_client.h
> @@ -108,6 +108,7 @@ enum ceph_osd_data_type {
> CEPH_OSD_DATA_TYPE_BIO,
> #endif /* CONFIG_BLOCK */
> CEPH_OSD_DATA_TYPE_BVECS,
> + CEPH_OSD_DATA_TYPE_ITER,
> };
>
> struct ceph_osd_data {
> @@ -131,6 +132,7 @@ struct ceph_osd_data {
> struct ceph_bvec_iter bvec_pos;
> u32 num_bvecs;
> };
> + struct iov_iter iter;
> };
> };
>
> @@ -501,6 +503,8 @@ void osd_req_op_extent_osd_data_bvecs(struct ceph_osd_request *osd_req,
> void osd_req_op_extent_osd_data_bvec_pos(struct ceph_osd_request *osd_req,
> unsigned int which,
> struct ceph_bvec_iter *bvec_pos);
> +void osd_req_op_extent_osd_iter(struct ceph_osd_request *osd_req,
> + unsigned int which, struct iov_iter *iter);
>
> extern void osd_req_op_cls_request_data_pagelist(struct ceph_osd_request *,
> unsigned int which,
> diff --git a/net/ceph/messenger.c b/net/ceph/messenger.c
> index 6056c8f7dd4c..cea0d75dfc49 100644
> --- a/net/ceph/messenger.c
> +++ b/net/ceph/messenger.c
> @@ -964,6 +964,48 @@ static bool ceph_msg_data_pagelist_advance(struct ceph_msg_data_cursor *cursor,
> return true;
> }
>
> +static void ceph_msg_data_iter_cursor_init(struct ceph_msg_data_cursor *cursor,
> + size_t length)
> +{
> + struct ceph_msg_data *data = cursor->data;
> +
> + cursor->iov_iter = data->iter;
> + iov_iter_truncate(&cursor->iov_iter, length);
> + cursor->resid = iov_iter_count(&cursor->iov_iter);
> +}
> +
> +static struct page *ceph_msg_data_iter_next(struct ceph_msg_data_cursor *cursor,
> + size_t *page_offset,
> + size_t *length)
> +{
> + struct page *page;
> + ssize_t len = iov_iter_get_pages(&cursor->iov_iter, &page, PAGE_SIZE,
> + 1, page_offset);
> +
> + BUG_ON(len < 0);
> +
> + /*
> + * The assumption is that the pages represented by the iov_iter are
> + * pinned, with the references held by the upper-level callers, or
> + * by virtue of being under writeback. Given that, we should be
> + * safe to put the page reference here and still return the pointer.
> + */
> + VM_BUG_ON_PAGE(!PageWriteback(page) && page_count(page) < 2, page);
> + put_page(page);
> + *length = min_t(size_t, len, cursor->resid);
> + return page;
> +}
> +
> +static bool ceph_msg_data_iter_advance(struct ceph_msg_data_cursor *cursor,
> + size_t bytes)
> +{
> + BUG_ON(bytes > cursor->resid);
> + cursor->resid -= bytes;
> + iov_iter_advance(&cursor->iov_iter, bytes);
> +
> + return cursor->resid;
> +}
> +
> /*
> * Message data is handled (sent or received) in pieces, where each
> * piece resides on a single page. The network layer might not
> @@ -991,6 +1033,9 @@ static void __ceph_msg_data_cursor_init(struct ceph_msg_data_cursor *cursor)
> case CEPH_MSG_DATA_BVECS:
> ceph_msg_data_bvecs_cursor_init(cursor, length);
> break;
> + case CEPH_MSG_DATA_ITER:
> + ceph_msg_data_iter_cursor_init(cursor, length);
> + break;
> case CEPH_MSG_DATA_NONE:
> default:
> /* BUG(); */
> @@ -1038,6 +1083,9 @@ struct page *ceph_msg_data_next(struct ceph_msg_data_cursor *cursor,
> case CEPH_MSG_DATA_BVECS:
> page = ceph_msg_data_bvecs_next(cursor, page_offset, length);
> break;
> + case CEPH_MSG_DATA_ITER:
> + page = ceph_msg_data_iter_next(cursor, page_offset, length);
> + break;
> case CEPH_MSG_DATA_NONE:
> default:
> page = NULL;
> @@ -1076,6 +1124,9 @@ void ceph_msg_data_advance(struct ceph_msg_data_cursor *cursor, size_t bytes)
> case CEPH_MSG_DATA_BVECS:
> new_piece = ceph_msg_data_bvecs_advance(cursor, bytes);
> break;
> + case CEPH_MSG_DATA_ITER:
> + new_piece = ceph_msg_data_iter_advance(cursor, bytes);
> + break;
> case CEPH_MSG_DATA_NONE:
> default:
> BUG();
> @@ -1874,6 +1925,19 @@ void ceph_msg_data_add_bvecs(struct ceph_msg *msg,
> }
> EXPORT_SYMBOL(ceph_msg_data_add_bvecs);
>
> +void ceph_msg_data_add_iter(struct ceph_msg *msg,
> + struct iov_iter *iter)
> +{
> + struct ceph_msg_data *data;
> +
> + data = ceph_msg_data_add(msg);
> + data->type = CEPH_MSG_DATA_ITER;
> + data->iter = *iter;
> +
> + msg->data_length += iov_iter_count(&data->iter);
> +}
> +EXPORT_SYMBOL(ceph_msg_data_add_iter);
I don't think this EXPORT_SYMBOL is actually needed. Nothing outside
libceph calls this. I've fixed this up in my tree, and can send a v2, or
you can just remove that line before merging.
> +
> /*
> * construct a new message with given type, size
> * the new msg has a ref count of 1.
> diff --git a/net/ceph/osd_client.c b/net/ceph/osd_client.c
> index 75761537c644..2a7e46524e71 100644
> --- a/net/ceph/osd_client.c
> +++ b/net/ceph/osd_client.c
> @@ -171,6 +171,13 @@ static void ceph_osd_data_bvecs_init(struct ceph_osd_data *osd_data,
> osd_data->num_bvecs = num_bvecs;
> }
>
> +static void ceph_osd_iter_init(struct ceph_osd_data *osd_data,
> + struct iov_iter *iter)
> +{
> + osd_data->type = CEPH_OSD_DATA_TYPE_ITER;
> + osd_data->iter = *iter;
> +}
> +
> static struct ceph_osd_data *
> osd_req_op_raw_data_in(struct ceph_osd_request *osd_req, unsigned int which)
> {
> @@ -264,6 +271,22 @@ void osd_req_op_extent_osd_data_bvec_pos(struct ceph_osd_request *osd_req,
> }
> EXPORT_SYMBOL(osd_req_op_extent_osd_data_bvec_pos);
>
> +/**
> + * osd_req_op_extent_osd_iter - Set up an operation with an iterator buffer
> + * @osd_req: The request to set up
> + * @which: ?
> + * @iter: The buffer iterator
> + */
> +void osd_req_op_extent_osd_iter(struct ceph_osd_request *osd_req,
> + unsigned int which, struct iov_iter *iter)
> +{
> + struct ceph_osd_data *osd_data;
> +
> + osd_data = osd_req_op_data(osd_req, which, extent, osd_data);
> + ceph_osd_iter_init(osd_data, iter);
> +}
> +EXPORT_SYMBOL(osd_req_op_extent_osd_iter);
> +
> static void osd_req_op_cls_request_info_pagelist(
> struct ceph_osd_request *osd_req,
> unsigned int which, struct ceph_pagelist *pagelist)
> @@ -346,6 +369,8 @@ static u64 ceph_osd_data_length(struct ceph_osd_data *osd_data)
> #endif /* CONFIG_BLOCK */
> case CEPH_OSD_DATA_TYPE_BVECS:
> return osd_data->bvec_pos.iter.bi_size;
> + case CEPH_OSD_DATA_TYPE_ITER:
> + return iov_iter_count(&osd_data->iter);
> default:
> WARN(true, "unrecognized data type %d\n", (int)osd_data->type);
> return 0;
> @@ -954,6 +979,8 @@ static void ceph_osdc_msg_data_add(struct ceph_msg *msg,
> #endif
> } else if (osd_data->type == CEPH_OSD_DATA_TYPE_BVECS) {
> ceph_msg_data_add_bvecs(msg, &osd_data->bvec_pos);
> + } else if (osd_data->type == CEPH_OSD_DATA_TYPE_ITER) {
> + ceph_msg_data_add_iter(msg, &osd_data->iter);
> } else {
> BUG_ON(osd_data->type != CEPH_OSD_DATA_TYPE_NONE);
> }
--
Jeff Layton <jlayton@xxxxxxxxxx>
