[PATCH v2 022/127] smb: smbdirect: introduce smbdirect_map_sges_from_iter() and helper functions

[Stefan Metzmacher]

These are basically copies of smb_extract_iter_to_rdma() and its helpers
in the client, which will be replaced in the next steps.

The goal is to use them also in the server, which will simplify a lot.

Cc: Steve French <smfrench at gmail.com>
Cc: Tom Talpey <tom at talpey.com>
Cc: Long Li <longli at microsoft.com>
Cc: Namjae Jeon <linkinjeon at kernel.org>
Cc: David Howells <dhowells at redhat.com>
Cc: linux-cifs at vger.kernel.org
Cc: samba-technical at lists.samba.org
Signed-off-by: Stefan Metzmacher <metze at samba.org>
Signed-off-by: Steve French <stfrench at microsoft.com>
---
 .../common/smbdirect/smbdirect_connection.c   | 255 ++++++++++++++++++
 1 file changed, 255 insertions(+)

diff --git a/fs/smb/common/smbdirect/smbdirect_connection.c b/fs/smb/common/smbdirect/smbdirect_connection.c
index dedc47916e0e..1113a7e9d575 100644
--- a/fs/smb/common/smbdirect/smbdirect_connection.c
+++ b/fs/smb/common/smbdirect/smbdirect_connection.c
@@ -5,6 +5,19 @@
  */
 
 #include "smbdirect_internal.h"
+#include <linux/folio_queue.h>
+
+struct smbdirect_map_sges {
+	struct ib_sge *sge;
+	size_t num_sge;
+	size_t max_sge;
+	struct ib_device *device;
+	u32 local_dma_lkey;
+	enum dma_data_direction direction;
+};
+
+static ssize_t smbdirect_map_sges_from_iter(struct iov_iter *iter, size_t len,
+					    struct smbdirect_map_sges *state);
 
 static void smbdirect_connection_schedule_disconnect(struct smbdirect_socket *sc,
 						     int error);
@@ -525,3 +538,245 @@ static void smbdirect_connection_send_io_done(struct ib_cq *cq, struct ib_wc *wc
 
 	wake_up(&sc->send_io.pending.dec_wait_queue);
 }
+
+static bool smbdirect_map_sges_single_page(struct smbdirect_map_sges *state,
+					   struct page *page, size_t off, size_t len)
+{
+	struct ib_sge *sge;
+	u64 addr;
+
+	if (state->num_sge >= state->max_sge)
+		return false;
+
+	addr = ib_dma_map_page(state->device, page,
+			       off, len, state->direction);
+	if (ib_dma_mapping_error(state->device, addr))
+		return false;
+
+	sge = &state->sge[state->num_sge++];
+	sge->addr   = addr;
+	sge->length = len;
+	sge->lkey   = state->local_dma_lkey;
+
+	return true;
+}
+
+/*
+ * Extract page fragments from a BVEC-class iterator and add them to an ib_sge
+ * list.  The pages are not pinned.
+ */
+static ssize_t smbdirect_map_sges_from_bvec(struct iov_iter *iter,
+					    struct smbdirect_map_sges *state,
+					    ssize_t maxsize)
+{
+	const struct bio_vec *bv = iter->bvec;
+	unsigned long start = iter->iov_offset;
+	unsigned int i;
+	ssize_t ret = 0;
+
+	for (i = 0; i < iter->nr_segs; i++) {
+		size_t off, len;
+		bool ok;
+
+		len = bv[i].bv_len;
+		if (start >= len) {
+			start -= len;
+			continue;
+		}
+
+		len = min_t(size_t, maxsize, len - start);
+		off = bv[i].bv_offset + start;
+
+		ok = smbdirect_map_sges_single_page(state,
+						    bv[i].bv_page,
+						    off,
+						    len);
+		if (!ok)
+			return -EIO;
+
+		ret += len;
+		maxsize -= len;
+		if (state->num_sge >= state->max_sge || maxsize <= 0)
+			break;
+		start = 0;
+	}
+
+	if (ret > 0)
+		iov_iter_advance(iter, ret);
+	return ret;
+}
+
+/*
+ * Extract fragments from a KVEC-class iterator and add them to an ib_sge list.
+ * This can deal with vmalloc'd buffers as well as kmalloc'd or static buffers.
+ * The pages are not pinned.
+ */
+static ssize_t smbdirect_map_sges_from_kvec(struct iov_iter *iter,
+					    struct smbdirect_map_sges *state,
+					    ssize_t maxsize)
+{
+	const struct kvec *kv = iter->kvec;
+	unsigned long start = iter->iov_offset;
+	unsigned int i;
+	ssize_t ret = 0;
+
+	for (i = 0; i < iter->nr_segs; i++) {
+		struct page *page;
+		unsigned long kaddr;
+		size_t off, len, seg;
+
+		len = kv[i].iov_len;
+		if (start >= len) {
+			start -= len;
+			continue;
+		}
+
+		kaddr = (unsigned long)kv[i].iov_base + start;
+		off = kaddr & ~PAGE_MASK;
+		len = min_t(size_t, maxsize, len - start);
+		kaddr &= PAGE_MASK;
+
+		maxsize -= len;
+		do {
+			bool ok;
+
+			seg = min_t(size_t, len, PAGE_SIZE - off);
+
+			if (is_vmalloc_or_module_addr((void *)kaddr))
+				page = vmalloc_to_page((void *)kaddr);
+			else
+				page = virt_to_page((void *)kaddr);
+
+			ok = smbdirect_map_sges_single_page(state, page, off, seg);
+			if (!ok)
+				return -EIO;
+
+			ret += seg;
+			len -= seg;
+			kaddr += PAGE_SIZE;
+			off = 0;
+		} while (len > 0 && state->num_sge < state->max_sge);
+
+		if (state->num_sge >= state->max_sge || maxsize <= 0)
+			break;
+		start = 0;
+	}
+
+	if (ret > 0)
+		iov_iter_advance(iter, ret);
+	return ret;
+}
+
+/*
+ * Extract folio fragments from a FOLIOQ-class iterator and add them to an
+ * ib_sge list.  The folios are not pinned.
+ */
+static ssize_t smbdirect_map_sges_from_folioq(struct iov_iter *iter,
+					      struct smbdirect_map_sges *state,
+					      ssize_t maxsize)
+{
+	const struct folio_queue *folioq = iter->folioq;
+	unsigned int slot = iter->folioq_slot;
+	ssize_t ret = 0;
+	size_t offset = iter->iov_offset;
+
+	if (WARN_ON_ONCE(!folioq))
+		return -EIO;
+
+	if (slot >= folioq_nr_slots(folioq)) {
+		folioq = folioq->next;
+		if (WARN_ON_ONCE(!folioq))
+			return -EIO;
+		slot = 0;
+	}
+
+	do {
+		struct folio *folio = folioq_folio(folioq, slot);
+		size_t fsize = folioq_folio_size(folioq, slot);
+
+		if (offset < fsize) {
+			size_t part = umin(maxsize, fsize - offset);
+			bool ok;
+
+			ok = smbdirect_map_sges_single_page(state,
+							    folio_page(folio, 0),
+							    offset,
+							    part);
+			if (!ok)
+				return -EIO;
+
+			offset += part;
+			ret += part;
+			maxsize -= part;
+		}
+
+		if (offset >= fsize) {
+			offset = 0;
+			slot++;
+			if (slot >= folioq_nr_slots(folioq)) {
+				if (!folioq->next) {
+					WARN_ON_ONCE(ret < iter->count);
+					break;
+				}
+				folioq = folioq->next;
+				slot = 0;
+			}
+		}
+	} while (state->num_sge < state->max_sge && maxsize > 0);
+
+	iter->folioq = folioq;
+	iter->folioq_slot = slot;
+	iter->iov_offset = offset;
+	iter->count -= ret;
+	return ret;
+}
+
+/*
+ * Extract page fragments from up to the given amount of the source iterator
+ * and build up an ib_sge list that refers to all of those bits.  The ib_sge list
+ * is appended to, up to the maximum number of elements set in the parameter
+ * block.
+ *
+ * The extracted page fragments are not pinned or ref'd in any way; if an
+ * IOVEC/UBUF-type iterator is to be used, it should be converted to a
+ * BVEC-type iterator and the pages pinned, ref'd or otherwise held in some
+ * way.
+ */
+__maybe_unused /* this is temporary while this file is included in orders */
+static ssize_t smbdirect_map_sges_from_iter(struct iov_iter *iter, size_t len,
+					    struct smbdirect_map_sges *state)
+{
+	ssize_t ret;
+	size_t before = state->num_sge;
+
+	if (WARN_ON_ONCE(iov_iter_rw(iter) != ITER_SOURCE))
+		return -EIO;
+
+	switch (iov_iter_type(iter)) {
+	case ITER_BVEC:
+		ret = smbdirect_map_sges_from_bvec(iter, state, len);
+		break;
+	case ITER_KVEC:
+		ret = smbdirect_map_sges_from_kvec(iter, state, len);
+		break;
+	case ITER_FOLIOQ:
+		ret = smbdirect_map_sges_from_folioq(iter, state, len);
+		break;
+	default:
+		WARN_ON_ONCE(1);
+		return -EIO;
+	}
+
+	if (ret < 0) {
+		while (state->num_sge > before) {
+			struct ib_sge *sge = &state->sge[state->num_sge--];
+
+			ib_dma_unmap_page(state->device,
+					  sge->addr,
+					  sge->length,
+					  state->direction);
+		}
+	}
+
+	return ret;
+}
-- 
2.43.0