introduce sg_pcopy_from_buffer() and sg_pcopy_to_buffer()

index a1cf8ca..c35b929 100644
@@ -453,6 +453,28 @@ void sg_miter_start(struct sg_mapping_iter *miter, struct scatterlist *sgl,
 }
 EXPORT_SYMBOL(sg_miter_start);
 
+static bool sg_miter_get_next_page(struct sg_mapping_iter *miter)
+{
+	if (!miter->__remaining) {
+		struct scatterlist *sg;
+		unsigned long pgoffset;
+
+		if (!__sg_page_iter_next(&miter->piter))
+			return false;
+
+		sg = miter->piter.sg;
+		pgoffset = miter->piter.sg_pgoffset;
+
+		miter->__offset = pgoffset ? 0 : sg->offset;
+		miter->__remaining = sg->offset + sg->length -
+				(pgoffset << PAGE_SHIFT) - miter->__offset;
+		miter->__remaining = min_t(unsigned long, miter->__remaining,
+					   PAGE_SIZE - miter->__offset);
+	}
+
+	return true;
+}
+
 /**
  * sg_miter_next - proceed mapping iterator to the next mapping
  * @miter: sg mapping iter to proceed

@@ -478,22 +500,9 @@ bool sg_miter_next(struct sg_mapping_iter *miter)
 	 * Get to the next page if necessary.
 	 * __remaining, __offset is adjusted by sg_miter_stop
 	 */
-	if (!miter->__remaining) {
-		struct scatterlist *sg;
-		unsigned long pgoffset;
-
-		if (!__sg_page_iter_next(&miter->piter))
-			return false;
-
-		sg = miter->piter.sg;
-		pgoffset = miter->piter.sg_pgoffset;
+	if (!sg_miter_get_next_page(miter))
+		return false;
 
-		miter->__offset = pgoffset ? 0 : sg->offset;
-		miter->__remaining = sg->offset + sg->length -
-				(pgoffset << PAGE_SHIFT) - miter->__offset;
-		miter->__remaining = min_t(unsigned long, miter->__remaining,
-					   PAGE_SIZE - miter->__offset);
-	}
 	miter->page = sg_page_iter_page(&miter->piter);
 	miter->consumed = miter->length = miter->__remaining;
 

index 2680677..adae88f 100644
@@ -244,6 +244,11 @@ size_t sg_copy_from_buffer(struct scatterlist *sgl, unsigned int nents,
 size_t sg_copy_to_buffer(struct scatterlist *sgl, unsigned int nents,
 			 void *buf, size_t buflen);
 
+size_t sg_pcopy_from_buffer(struct scatterlist *sgl, unsigned int nents,
+			    void *buf, size_t buflen, off_t skip);
+size_t sg_pcopy_to_buffer(struct scatterlist *sgl, unsigned int nents,
+			  void *buf, size_t buflen, off_t skip);
+
 /*
  * Maximum number of entries that will be allocated in one piece, if
  * a list larger than this is required then chaining will be utilized.

122 lines not on this page · raw message

index 5b2b5e6..661dc3e 100644
@@ -1112,64 +1112,6 @@ static int sg_count(struct scatterlist *sg_list, int nbytes, bool *chained)
 	return sg_nents;
 }
 
-/**
- * sg_copy_end_to_buffer - Copy end data from SG list to a linear buffer
- * @sgl:		 The SG list
- * @nents:		 Number of SG entries
- * @buf:		 Where to copy to
- * @buflen:		 The number of bytes to copy
- * @skip:		 The number of bytes to skip before copying.
- *                       Note: skip + buflen should equal SG total size.
- *
- * Returns the number of copied bytes.
- *
- **/
-static size_t sg_copy_end_to_buffer(struct scatterlist *sgl, unsigned int nents,
-				    void *buf, size_t buflen, unsigned int skip)
-{
-	unsigned int offset = 0;
-	unsigned int boffset = 0;
-	struct sg_mapping_iter miter;
-	unsigned long flags;
-	unsigned int sg_flags = SG_MITER_ATOMIC;
-	size_t total_buffer = buflen + skip;
-
-	sg_flags |= SG_MITER_FROM_SG;
-
-	sg_miter_start(&miter, sgl, nents, sg_flags);
-
-	local_irq_save(flags);
-
-	while (sg_miter_next(&miter) && offset < total_buffer) {
-		unsigned int len;
-		unsigned int ignore;
-
-		if ((offset + miter.length) > skip) {
-			if (offset < skip) {
-				/* Copy part of this segment */
-				ignore = skip - offset;
-				len = miter.length - ignore;
-				if (boffset + len > buflen)
-					len = buflen - boffset;
-				memcpy(buf + boffset, miter.addr + ignore, len);
-			} else {
-				/* Copy all of this segment (up to buflen) */
-				len = miter.length;
-				if (boffset + len > buflen)
-					len = buflen - boffset;
-				memcpy(buf + boffset, miter.addr, len);
-			}
-			boffset += len;
-		}
-		offset += miter.length;
-	}
-
-	sg_miter_stop(&miter);
-
-	local_irq_restore(flags);
-	return boffset;
-}
-
 /*
  * allocate and map the extended descriptor
  */

@@ -1800,7 +1742,7 @@ static int ahash_process_req(struct ahash_request *areq, unsigned int nbytes)
 
 	if (to_hash_later) {
 		int nents = sg_count(areq->src, nbytes, &chained);
-		sg_copy_end_to_buffer(areq->src, nents,
+		sg_pcopy_to_buffer(areq->src, nents,
 				      req_ctx->bufnext,
 				      to_hash_later,
 				      nbytes - to_hash_later);

index 21239b3..1b15f98 100644
@@ -417,10 +417,7 @@ static int fill_from_dev_buffer(struct scsi_cmnd *scp, unsigned char *arr,
 
 	act_len = sg_copy_from_buffer(sdb->table.sgl, sdb->table.nents,
 				      arr, arr_len);
-	if (sdb->resid)
-		sdb->resid -= act_len;
-	else
-		sdb->resid = scsi_bufflen(scp) - act_len;
+	sdb->resid = scsi_bufflen(scp) - act_len;
 
 	return 0;
 }

@@ -1614,24 +1611,48 @@ static int check_device_access_params(struct sdebug_dev_info *devi,
 	return 0;
 }
 
+/* Returns number of bytes copied or -1 if error. */
 static int do_device_access(struct scsi_cmnd *scmd,
 			    struct sdebug_dev_info *devi,
 			    unsigned long long lba, unsigned int num, int write)
 {
 	int ret;
 	unsigned long long block, rest = 0;
-	int (*func)(struct scsi_cmnd *, unsigned char *, int);
+	struct scsi_data_buffer *sdb;
+	enum dma_data_direction dir;
+	size_t (*func)(struct scatterlist *, unsigned int, void *, size_t,
+		       off_t);
+
+	if (write) {
+		sdb = scsi_out(scmd);
+		dir = DMA_TO_DEVICE;
+		func = sg_pcopy_to_buffer;
+	} else {
+		sdb = scsi_in(scmd);
+		dir = DMA_FROM_DEVICE;
+		func = sg_pcopy_from_buffer;
+	}
 
-	func = write ? fetch_to_dev_buffer : fill_from_dev_buffer;
+	if (!sdb->length)
+		return 0;
+	if (!(scsi_bidi_cmnd(scmd) || scmd->sc_data_direction == dir))
+		return -1;
 
 	block = do_div(lba, sdebug_store_sectors);
 	if (block + num > sdebug_store_sectors)
 		rest = block + num - sdebug_store_sectors;
 
-	ret = func(scmd, fake_storep + (block * scsi_debug_sector_size),
-		   (num - rest) * scsi_debug_sector_size);
-	if (!ret && rest)
-		ret = func(scmd, fake_storep, rest * scsi_debug_sector_size);
+	ret = func(sdb->table.sgl, sdb->table.nents,
+		   fake_storep + (block * scsi_debug_sector_size),
+		   (num - rest) * scsi_debug_sector_size, 0);
+	if (ret != (num - rest) * scsi_debug_sector_size)
+		return ret;
+
+	if (rest) {
+		ret += func(sdb->table.sgl, sdb->table.nents,
+			    fake_storep, rest * scsi_debug_sector_size,
+			    (num - rest) * scsi_debug_sector_size);
+	}
 
 	return ret;
 }

@@ -1888,7 +1909,12 @@ static int resp_read(struct scsi_cmnd *SCpnt, unsigned long long lba,
 	read_lock_irqsave(&atomic_rw, iflags);
 	ret = do_device_access(SCpnt, devip, lba, num, 0);
 	read_unlock_irqrestore(&atomic_rw, iflags);
-	return ret;
+	if (ret == -1)
+		return DID_ERROR << 16;
+
+	scsi_in(SCpnt)->resid = scsi_bufflen(SCpnt) - ret;
+
+	return 0;
 }
 
 static void dump_sector(unsigned char *buf, int len)