On Fri, 2022-07-01 at 10:04 +0800, Xiubo Li wrote:
> On 6/27/22 11:54 PM, 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.
> >
> > We assume that the pages represented by the iter are pinned such that
> > they shouldn't incur page faults, which is the case for the iov_iters
> > created by netfs.
> >
> > While working on this, Al Viro informed me that he was going to change
> > iov_iter_get_pages to auto-advance the iterator as that pattern is more
> > or less required for ITER_PIPE anyway. We emulate that here for now by
> > advancing in the _next op and tracking that amount in the "lastlen"
> > field.
> >
> > In the event that _next is called twice without an intervening
> > _advance, we revert the iov_iter by the remaining lastlen before
> > calling iov_iter_get_pages.
> >
> > Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
> > Cc: David Howells <dhowells@xxxxxxxxxx>
> > Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx>
> > ---
> > include/linux/ceph/messenger.h | 8 ++++
> > include/linux/ceph/osd_client.h | 4 ++
> > net/ceph/messenger.c | 85 +++++++++++++++++++++++++++++++++
> > net/ceph/osd_client.c | 27 +++++++++++
> > 4 files changed, 124 insertions(+)
> >
> > diff --git a/include/linux/ceph/messenger.h b/include/linux/ceph/messenger.h
> > index 9fd7255172ad..2eaaabbe98cb 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 +250,10 @@ struct ceph_msg_data_cursor {
> > struct page *page; /* page from list */
> > size_t offset; /* bytes from list */
> > };
> > + struct {
> > + struct iov_iter iov_iter;
> > + unsigned int lastlen;
> > + };
> > };
> > };
> >
> > @@ -605,6 +611,8 @@ 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..604f025034ab 100644
> > --- a/net/ceph/messenger.c
> > +++ b/net/ceph/messenger.c
> > @@ -964,6 +964,69 @@ 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;
> > + cursor->lastlen = 0;
> > + 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;
> > +
> > + if (cursor->lastlen)
> > + iov_iter_revert(&cursor->iov_iter, cursor->lastlen);
> > +
> > + len = iov_iter_get_pages(&cursor->iov_iter, &page, PAGE_SIZE,
> > + 1, page_offset);
> > + BUG_ON(len < 0);
> > +
> > + cursor->lastlen = len;
> > +
> > + /*
> > + * FIXME: Al Viro says that he will soon change iov_iter_get_pages
> > + * to auto-advance the iterator. Emulate that here for now.
> > + */
> > + iov_iter_advance(&cursor->iov_iter, len);
> > +
> > + /*
> > + * FIXME: 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. Eventually,
> > + * we'll get an iov_iter_get_pages variant that doesn't take page
> > + * refs. Until then, just put the page ref.
> > + */
> > + 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;
> > +
> > + if (bytes < cursor->lastlen) {
> > + cursor->lastlen -= bytes;
> > + } else {
> > + iov_iter_advance(&cursor->iov_iter, bytes - cursor->lastlen);
> > + cursor->lastlen = 0;
> > + }
> > +
> > + 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 +1054,9 @@ 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 +1104,9 @@ 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 +1145,9 @@ 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 +1946,19 @@ 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);
> > +
>
> Will this be used outside the libceph.ko ? It seem will never ? And also
> some other existing ones like 'ceph_msg_data_add_bvecs'.
>
No, I don't think it will. We can probably remove that.
> > /*
> > * 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: ?
>
> For this could you explain more ?
>
>
Sure. I'll respin and flesh out this comment.
> > + * @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>
