dif: Use struct dif_sgl to simplify to create iovec array

struct dif_sgl had been used only to iterate the passed iovec
array. This patch utilizes struct dif_sgl and adds a helper
function _dif_sgl_append() to simplify to create iovec array.

_dif_sgl_append() is a static function and we have to add
the callee together when we add any static function.

So this patch adds both even if the patch size is a little
larger.

Besides, iovcnt has been used to mean the number of elements
in the iovec array widely in the DIF library. So this patch
changes the name of it from num_iovs to iovcnt.

Change-Id: I1db4abc8ed4d2c107fe01ec6592f5f6731dc5520
Signed-off-by: Shuhei Matsumoto <shuhei.matsumoto.xt@hitachi.com>
Reviewed-on: https://review.gerrithub.io/c/spdk/spdk/+/454558
Tested-by: SPDK CI Jenkins <sys_sgci@intel.com>
Reviewed-by: Changpeng Liu <changpeng.liu@intel.com>
Reviewed-by: Jim Harris <james.r.harris@intel.com>

include/spdk/dif.h

@@ -268,7 +268,7 @@ int spdk_dix_inject_error(struct iovec *iovs, int iovcnt, struct iovec *md_iov,
  * during DIF insertion and strip.
  *
  * \param iovs iovec array set by this function.
- * \param num_iovs Number of elements in the iovec array.
+ * \param iovcnt Number of elements in the iovec array.
  * \param buf Buffer to create extended LBA payload.
  * \param buf_len Length of the buffer to create extended LBA payload.
  * \param data_offset Offset to store the next incoming data.
@@ -280,7 +280,7 @@ int spdk_dix_inject_error(struct iovec *iovs, int iovcnt, struct iovec *md_iov,
  * \return Number of used elements in the iovec array on success or negated
  * errno otherwise.
  */
-int spdk_dif_set_md_interleave_iovs(struct iovec *iovs, int num_iovs,
+int spdk_dif_set_md_interleave_iovs(struct iovec *iovs, int iovcnt,
 				    uint8_t *buf, uint32_t buf_len,
 				    uint32_t data_offset, uint32_t data_len,
 				    uint32_t *mapped_len,

lib/util/dif.c

@@ -37,16 +37,21 @@
 #include "spdk/log.h"
 #include "spdk/util.h"
 
-/* Context to iterate a iovec array. */
+/* Context to iterate or create a iovec array.
+ * Each sgl is either iterated or created at a time.
+ */
 struct _dif_sgl {
-	/* Current iovec in the iteration */
+	/* Current iovec in the iteration or iteration */
 	struct iovec *iov;
 
-	/* Remaining count of iovecs in the iteration. */
+	/* Remaining count of iovecs in the iteration or iteration. */
 	int iovcnt;
 
 	/* Current offset in the iovec */
 	uint32_t iov_offset;
+
+	/* Size of the created iovec array in bytes */
+	uint32_t total_size;
 };
 
 static inline void
@@ -55,6 +60,7 @@ _dif_sgl_init(struct _dif_sgl *s, struct iovec *iovs, int iovcnt)
 	s->iov = iovs;
 	s->iovcnt = iovcnt;
 	s->iov_offset = 0;
+	s->total_size = 0;
 }
 
 static inline void
@@ -95,6 +101,23 @@ _dif_sgl_fast_forward(struct _dif_sgl *s, uint32_t offset)
 	}
 }
 
+static inline bool
+_dif_sgl_append(struct _dif_sgl *s, uint8_t *data, uint32_t data_len)
+{
+	assert(s->iovcnt > 0);
+	s->iov->iov_base = data;
+	s->iov->iov_len = data_len;
+	s->total_size += data_len;
+	s->iov++;
+	s->iovcnt--;
+
+	if (s->iovcnt > 0) {
+		return true;
+	} else {
+		return false;
+	}
+}
+
 /* This function must be used before starting iteration. */
 static bool
 _dif_sgl_is_bytes_multiple(struct _dif_sgl *s, uint32_t bytes)
@@ -1263,18 +1286,17 @@ spdk_dix_inject_error(struct iovec *iovs, int iovcnt, struct iovec *md_iov,
 }
 
 int
-spdk_dif_set_md_interleave_iovs(struct iovec *iovs, int num_iovs,
+spdk_dif_set_md_interleave_iovs(struct iovec *iovs, int iovcnt,
 				uint8_t *buf, uint32_t buf_len,
 				uint32_t data_offset, uint32_t data_len,
 				uint32_t *_mapped_len,
 				const struct spdk_dif_ctx *ctx)
 {
-	uint32_t data_block_size, head_unalign, mapped_len = 0;
+	uint32_t data_block_size, head_unalign;
 	uint32_t num_blocks, offset_blocks;
-	struct iovec *iov = iovs;
+	struct _dif_sgl sgl;
-	int iovcnt = 0;
 
-	if (iovs == NULL || num_iovs == 0) {
+	if (iovs == NULL || iovcnt == 0) {
 		return -EINVAL;
 	}
 
@@ -1302,37 +1324,34 @@ spdk_dif_set_md_interleave_iovs(struct iovec *iovs, int num_iovs,
 	offset_blocks = data_offset / data_block_size;
 	head_unalign = data_offset % data_block_size;
 
+	_dif_sgl_init(&sgl, iovs, iovcnt);
 	buf += offset_blocks * ctx->block_size;
 
 	if (head_unalign != 0) {
 		buf += head_unalign;
 
-		iov->iov_base = buf;
+		if (!_dif_sgl_append(&sgl, buf, data_block_size - head_unalign)) {
-		iov->iov_len = data_block_size - head_unalign;
+			goto end;
-		mapped_len += data_block_size - head_unalign;
+		}
-		iov++;
-		iovcnt++;
 
 		buf += ctx->block_size - head_unalign;
 		offset_blocks++;
 	}
 
-	while (offset_blocks < num_blocks && iovcnt < num_iovs) {
+	while (offset_blocks < num_blocks) {
-		iov->iov_base = buf;
+		if (!_dif_sgl_append(&sgl, buf, data_block_size)) {
-		iov->iov_len = data_block_size;
+			goto end;
-		mapped_len += data_block_size;
+		}
-		iov++;
-		iovcnt++;
-
 		buf += ctx->block_size;
 		offset_blocks++;
 	}
 
+end:
 	if (_mapped_len != NULL) {
-		*_mapped_len = mapped_len;
+		*_mapped_len = sgl.total_size;
 	}
 
-	return iovcnt;
+	return iovcnt - sgl.iovcnt;
 }
 
 int