scsi: target: tcmu: Support DATA_BLOCK_SIZE = N * PAGE_SIZE

Change tcmu to support DATA_BLOCK_SIZE being a multiple of PAGE_SIZE. There
are two reasons why one would like to have a bigger DATA_BLOCK_SIZE:

 1) If userspace - e.g. due to data compression, encryption or
    deduplication - needs to have receive or transmit data in a consecutive
    buffer, we can define DATA_BLOCK_SIZE to the maximum size of a SCSI
    READ/WRITE to enforce that userspace sees just one consecutive
    buffer. That way we can avoid the need for doing data copy in
    userspace.

 2) Using a bigger data block size can speed up command processing in
    tcmu. The number of free data blocks to look up in bitmap is reduced
    substantially. The lookup for data pages in radix_tree can be done more
    efficiently if there are multiple pages in a data block. The maximum
    number of IOVs to set up is lower so cmd entries in the ring become
    smaller.

Link: https://lore.kernel.org/r/20210324195758.2021-4-bostroesser@gmail.com
Signed-off-by: Bodo Stroesser <bostroesser@gmail.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/target/target_core_user.c

@@ -67,14 +67,14 @@
 #define CMDR_SIZE (MB_CMDR_SIZE - CMDR_OFF)
 
 /*
- * For data area, the block size is PAGE_SIZE and
- * the total size is 256K * PAGE_SIZE.
+ * For data area, the default block size is PAGE_SIZE and
+ * the default total size is 256K * PAGE_SIZE.
  */
-#define DATA_BLOCK_SIZE PAGE_SIZE
 #define DATA_PAGES_PER_BLK 1
-#define DATA_BLOCK_BITS_DEF (256 * 1024)
+#define DATA_BLOCK_SIZE (DATA_PAGES_PER_BLK * PAGE_SIZE)
+#define DATA_AREA_PAGES_DEF (256 * 1024)
 
-#define TCMU_MBS_TO_PAGES(_mbs) (_mbs << (20 - PAGE_SHIFT))
+#define TCMU_MBS_TO_PAGES(_mbs) ((size_t)_mbs << (20 - PAGE_SHIFT))
 #define TCMU_PAGES_TO_MBS(_pages) (_pages >> (20 - PAGE_SHIFT))
 
 /*
@@ -138,7 +138,7 @@ struct tcmu_dev {
 	/* Offset of data area from start of mb */
 	/* Must add data_off and mb_addr to get the address */
 	size_t data_off;
-	size_t data_size;
+	int data_area_mb;
 	uint32_t max_blocks;
 	size_t mmap_pages;
 
@@ -501,31 +501,39 @@ static void tcmu_cmd_free_data(struct tcmu_cmd *tcmu_cmd, uint32_t len)
 
 static inline int tcmu_get_empty_block(struct tcmu_dev *udev,
 				       struct tcmu_cmd *tcmu_cmd,
-				       int prev_dbi, int *iov_cnt)
+				       int prev_dbi, int length, int *iov_cnt)
 {
+	XA_STATE(xas, &udev->data_pages, 0);
 	struct page *page;
-	int dbi;
+	int i, cnt, dbi;
+	int page_cnt = DIV_ROUND_UP(length, PAGE_SIZE);
 
 	dbi = find_first_zero_bit(udev->data_bitmap, udev->dbi_thresh);
 	if (dbi == udev->dbi_thresh)
 		return -1;
 
-	page = xa_load(&udev->data_pages, dbi);
-	if (!page) {
-		if (atomic_add_return(1, &global_page_count) >
-				      tcmu_global_max_pages)
-			schedule_delayed_work(&tcmu_unmap_work, 0);
+	/* Count the number of already allocated pages */
+	xas_set(&xas, dbi * DATA_PAGES_PER_BLK);
+	for (cnt = 0; xas_next(&xas) && cnt < page_cnt;)
+		cnt++;
 
+	for (i = cnt; i < page_cnt; i++) {
 		/* try to get new page from the mm */
 		page = alloc_page(GFP_NOIO);
 		if (!page)
-			goto err_alloc;
+			break;
 
-		if (xa_store(&udev->data_pages, dbi, page, GFP_NOIO))
-			goto err_insert;
+		if (xa_store(&udev->data_pages, dbi * DATA_PAGES_PER_BLK + i,
+			     page, GFP_NOIO)) {
+			__free_page(page);
+			break;
+		}
 	}
+	if (atomic_add_return(i - cnt, &global_page_count) >
+			      tcmu_global_max_pages)
+		schedule_delayed_work(&tcmu_unmap_work, 0);
 
-	if (dbi > udev->dbi_max)
+	if (i && dbi > udev->dbi_max)
 		udev->dbi_max = dbi;
 
 	set_bit(dbi, udev->data_bitmap);
@@ -534,23 +542,19 @@ static inline int tcmu_get_empty_block(struct tcmu_dev *udev,
 	if (dbi != prev_dbi + 1)
 		*iov_cnt += 1;
 
-	return dbi;
-err_insert:
-	__free_page(page);
-err_alloc:
-	atomic_dec(&global_page_count);
-	return -1;
+	return i == page_cnt ? dbi : -1;
 }
 
 static int tcmu_get_empty_blocks(struct tcmu_dev *udev,
-				 struct tcmu_cmd *tcmu_cmd, int dbi_cnt)
+				 struct tcmu_cmd *tcmu_cmd, int length)
 {
 	/* start value of dbi + 1 must not be a valid dbi */
 	int dbi = -2;
-	int i, iov_cnt = 0;
+	int blk_len, iov_cnt = 0;
 
-	for (i = 0; i < dbi_cnt; i++) {
-		dbi = tcmu_get_empty_block(udev, tcmu_cmd, dbi, &iov_cnt);
+	for (; length > 0; length -= DATA_BLOCK_SIZE) {
+		blk_len = min_t(int, length, DATA_BLOCK_SIZE);
+		dbi = tcmu_get_empty_block(udev, tcmu_cmd, dbi, blk_len, &iov_cnt);
 		if (dbi < 0)
 			return -1;
 	}
@@ -698,9 +702,11 @@ static inline void tcmu_copy_data(struct tcmu_dev *udev,
 				  struct scatterlist *sg, unsigned int sg_nents,
 				  struct iovec **iov, size_t data_len)
 {
+	XA_STATE(xas, &udev->data_pages, 0);
 	/* start value of dbi + 1 must not be a valid dbi */
 	int dbi = -2;
-	size_t block_remaining, cp_len;
+	size_t page_remaining, cp_len;
+	int page_cnt, page_inx;
 	struct sg_mapping_iter sg_iter;
 	unsigned int sg_flags;
 	struct page *page;
@@ -718,37 +724,48 @@ static inline void tcmu_copy_data(struct tcmu_dev *udev,
 					       data_len);
 		else
 			dbi = tcmu_cmd_get_dbi(tcmu_cmd);
-		page = tcmu_get_block_page(udev, dbi);
-		if (direction == TCMU_DATA_AREA_TO_SG)
-			flush_dcache_page(page);
-		data_page_start = kmap_atomic(page);
-		block_remaining = DATA_BLOCK_SIZE;
-
-		while (block_remaining && data_len) {
-			if (!sg_miter_next(&sg_iter)) {
-				/* set length to 0 to abort outer loop */
-				data_len = 0;
-				pr_debug("tcmu_move_data: aborting data copy due to exhausted sg_list\n");
-				break;
+
+		page_cnt = DIV_ROUND_UP(data_len, PAGE_SIZE);
+		if (page_cnt > DATA_PAGES_PER_BLK)
+			page_cnt = DATA_PAGES_PER_BLK;
+
+		xas_set(&xas, dbi * DATA_PAGES_PER_BLK);
+		for (page_inx = 0; page_inx < page_cnt && data_len; page_inx++) {
+			page = xas_next(&xas);
+
+			if (direction == TCMU_DATA_AREA_TO_SG)
+				flush_dcache_page(page);
+			data_page_start = kmap_atomic(page);
+			page_remaining = PAGE_SIZE;
+
+			while (page_remaining && data_len) {
+				if (!sg_miter_next(&sg_iter)) {
+					/* set length to 0 to abort outer loop */
+					data_len = 0;
+					pr_debug("%s: aborting data copy due to exhausted sg_list\n",
+						 __func__);
+					break;
+				}
+				cp_len = min3(sg_iter.length, page_remaining,
+					      data_len);
+
+				data_addr = data_page_start +
+					    PAGE_SIZE - page_remaining;
+				if (direction == TCMU_SG_TO_DATA_AREA)
+					memcpy(data_addr, sg_iter.addr, cp_len);
+				else
+					memcpy(sg_iter.addr, data_addr, cp_len);
+
+				data_len -= cp_len;
+				page_remaining -= cp_len;
+				sg_iter.consumed = cp_len;
 			}
-			cp_len = min3(sg_iter.length, block_remaining, data_len);
+			sg_miter_stop(&sg_iter);
 
-			data_addr = data_page_start +
-				    DATA_BLOCK_SIZE - block_remaining;
+			kunmap_atomic(data_page_start);
 			if (direction == TCMU_SG_TO_DATA_AREA)
-				memcpy(data_addr, sg_iter.addr, cp_len);
-			else
-				memcpy(sg_iter.addr, data_addr, cp_len);
-
-			data_len -= cp_len;
-			block_remaining -= cp_len;
-			sg_iter.consumed = cp_len;
+				flush_dcache_page(page);
 		}
-		sg_miter_stop(&sg_iter);
-
-		kunmap_atomic(data_page_start);
-		if (direction == TCMU_SG_TO_DATA_AREA)
-			flush_dcache_page(page);
 	}
 }
 
@@ -858,13 +875,12 @@ static int tcmu_alloc_data_space(struct tcmu_dev *udev, struct tcmu_cmd *cmd,
 			udev->dbi_thresh = udev->max_blocks;
 	}
 
-	iov_cnt = tcmu_get_empty_blocks(udev, cmd,
-					cmd->dbi_cnt - cmd->dbi_bidi_cnt);
+	iov_cnt = tcmu_get_empty_blocks(udev, cmd, cmd->se_cmd->data_length);
 	if (iov_cnt < 0)
 		return -1;
 
 	if (cmd->dbi_bidi_cnt) {
-		ret = tcmu_get_empty_blocks(udev, cmd, cmd->dbi_bidi_cnt);
+		ret = tcmu_get_empty_blocks(udev, cmd, cmd->data_len_bidi);
 		if (ret < 0)
 			return -1;
 	}
@@ -1020,9 +1036,9 @@ static int queue_cmd_ring(struct tcmu_cmd *tcmu_cmd, sense_reason_t *scsi_err)
 	if (!list_empty(&udev->qfull_queue))
 		goto queue;
 
-	if (data_length > udev->data_size) {
+	if (data_length > udev->max_blocks * DATA_BLOCK_SIZE) {
 		pr_warn("TCMU: Request of size %zu is too big for %zu data area\n",
-			data_length, udev->data_size);
+			data_length, udev->max_blocks * DATA_BLOCK_SIZE);
 		*scsi_err = TCM_INVALID_CDB_FIELD;
 		return -1;
 	}
@@ -1570,7 +1586,8 @@ static struct se_device *tcmu_alloc_device(struct se_hba *hba, const char *name)
 	udev->cmd_time_out = TCMU_TIME_OUT;
 	udev->qfull_time_out = -1;
 
-	udev->max_blocks = DATA_BLOCK_BITS_DEF;
+	udev->max_blocks = DATA_AREA_PAGES_DEF / DATA_PAGES_PER_BLK;
+	udev->data_area_mb = TCMU_PAGES_TO_MBS(DATA_AREA_PAGES_DEF);
 	mutex_init(&udev->cmdr_lock);
 
 	INIT_LIST_HEAD(&udev->node);
@@ -1607,19 +1624,24 @@ static int tcmu_check_and_free_pending_cmd(struct tcmu_cmd *cmd)
 	return -EINVAL;
 }
 
-static void tcmu_blocks_release(struct xarray *blocks, unsigned long first,
+static u32 tcmu_blocks_release(struct xarray *blocks, unsigned long first,
 				unsigned long last)
 {
-	XA_STATE(xas, blocks, first);
+	XA_STATE(xas, blocks, first * DATA_PAGES_PER_BLK);
 	struct page *page;
+	u32 pages_freed = 0;
 
 	xas_lock(&xas);
-	xas_for_each(&xas, page, last) {
+	xas_for_each(&xas, page, (last + 1) * DATA_PAGES_PER_BLK - 1) {
 		xas_store(&xas, NULL);
 		__free_page(page);
-		atomic_dec(&global_page_count);
+		pages_freed++;
 	}
 	xas_unlock(&xas);
+
+	atomic_sub(pages_freed, &global_page_count);
+
+	return pages_freed;
 }
 
 static void tcmu_remove_all_queued_tmr(struct tcmu_dev *udev)
@@ -2086,6 +2108,7 @@ static int tcmu_configure_device(struct se_device *dev)
 	struct tcmu_dev *udev = TCMU_DEV(dev);
 	struct uio_info *info;
 	struct tcmu_mailbox *mb;
+	size_t data_size;
 	int ret = 0;
 
 	ret = tcmu_update_uio_info(udev);
@@ -2113,8 +2136,8 @@ static int tcmu_configure_device(struct se_device *dev)
 	udev->cmdr = (void *)mb + CMDR_OFF;
 	udev->cmdr_size = CMDR_SIZE;
 	udev->data_off = MB_CMDR_SIZE;
-	udev->data_size = udev->max_blocks * DATA_BLOCK_SIZE;
-	udev->mmap_pages = (udev->data_size + MB_CMDR_SIZE) >> PAGE_SHIFT;
+	data_size = TCMU_MBS_TO_PAGES(udev->data_area_mb) << PAGE_SHIFT;
+	udev->mmap_pages = (data_size + MB_CMDR_SIZE) >> PAGE_SHIFT;
 	udev->dbi_thresh = 0; /* Default in Idle state */
 
 	/* Initialise the mailbox of the ring buffer */
@@ -2126,14 +2149,13 @@ static int tcmu_configure_device(struct se_device *dev)
 	mb->cmdr_size = udev->cmdr_size;
 
 	WARN_ON(!PAGE_ALIGNED(udev->data_off));
-	WARN_ON(udev->data_size % PAGE_SIZE);
-	WARN_ON(udev->data_size % DATA_BLOCK_SIZE);
+	WARN_ON(data_size % PAGE_SIZE);
 
 	info->version = __stringify(TCMU_MAILBOX_VERSION);
 
 	info->mem[0].name = "tcm-user command & data buffer";
 	info->mem[0].addr = (phys_addr_t)(uintptr_t)udev->mb_addr;
-	info->mem[0].size = udev->data_size + MB_CMDR_SIZE;
+	info->mem[0].size = data_size + MB_CMDR_SIZE;
 	info->mem[0].memtype = UIO_MEM_NONE;
 
 	info->irqcontrol = tcmu_irqcontrol;
@@ -2343,20 +2365,28 @@ static int tcmu_set_dev_attrib(substring_t *arg, u32 *dev_attrib)
 
 static int tcmu_set_max_blocks_param(struct tcmu_dev *udev, substring_t *arg)
 {
-	int val, ret, blks;
+	int val, ret;
 
 	ret = match_int(arg, &val);
 	if (ret < 0) {
 		pr_err("match_int() failed for max_data_area_mb=. Error %d.\n",
 		       ret);
 		return ret;
 	}
-
-	blks = TCMU_MBS_TO_PAGES(val) / DATA_PAGES_PER_BLK;
-	if (blks <= 0) {
+	if (val <= 0) {
 		pr_err("Invalid max_data_area %d.\n", val);
 		return -EINVAL;
 	}
+	if (val > TCMU_PAGES_TO_MBS(tcmu_global_max_pages)) {
+		pr_err("%d is too large. Adjusting max_data_area_mb to global limit of %u\n",
+		       val, TCMU_PAGES_TO_MBS(tcmu_global_max_pages));
+		val = TCMU_PAGES_TO_MBS(tcmu_global_max_pages);
+	}
+	if (TCMU_MBS_TO_PAGES(val) < DATA_PAGES_PER_BLK) {
+		pr_err("Invalid max_data_area %d (%zu pages): smaller than data_pages_per_blk (%d pages).\n",
+		       val, TCMU_MBS_TO_PAGES(val), DATA_PAGES_PER_BLK);
+		return -EINVAL;
+	}
 
 	mutex_lock(&udev->cmdr_lock);
 	if (udev->data_bitmap) {
@@ -2365,12 +2395,8 @@ static int tcmu_set_max_blocks_param(struct tcmu_dev *udev, substring_t *arg)
 		goto unlock;
 	}
 
-	udev->max_blocks = blks;
-	if (udev->max_blocks * DATA_PAGES_PER_BLK > tcmu_global_max_pages) {
-		pr_err("%d is too large. Adjusting max_data_area_mb to global limit of %u\n",
-		       val, TCMU_PAGES_TO_MBS(tcmu_global_max_pages));
-		udev->max_blocks = tcmu_global_max_pages / DATA_PAGES_PER_BLK;
-	}
+	udev->data_area_mb = val;
+	udev->max_blocks = TCMU_MBS_TO_PAGES(val) / DATA_PAGES_PER_BLK;
 
 unlock:
 	mutex_unlock(&udev->cmdr_lock);
@@ -2448,8 +2474,7 @@ static ssize_t tcmu_show_configfs_dev_params(struct se_device *dev, char *b)
 	bl = sprintf(b + bl, "Config: %s ",
 		     udev->dev_config[0] ? udev->dev_config : "NULL");
 	bl += sprintf(b + bl, "Size: %llu ", udev->dev_size);
-	bl += sprintf(b + bl, "MaxDataAreaMB: %u\n",
-		      TCMU_PAGES_TO_MBS(udev->max_blocks * DATA_PAGES_PER_BLK));
+	bl += sprintf(b + bl, "MaxDataAreaMB: %u\n", udev->data_area_mb);
 
 	return bl;
 }
@@ -2543,8 +2568,7 @@ static ssize_t tcmu_max_data_area_mb_show(struct config_item *item, char *page)
 						struct se_dev_attrib, da_group);
 	struct tcmu_dev *udev = TCMU_DEV(da->da_dev);
 
-	return snprintf(page, PAGE_SIZE, "%u\n",
-			TCMU_PAGES_TO_MBS(udev->max_blocks * DATA_PAGES_PER_BLK));
+	return snprintf(page, PAGE_SIZE, "%u\n", udev->data_area_mb);
 }
 CONFIGFS_ATTR_RO(tcmu_, max_data_area_mb);
 
@@ -2902,7 +2926,8 @@ static void find_free_blocks(void)
 {
 	struct tcmu_dev *udev;
 	loff_t off;
-	u32 start, end, block, total_freed = 0;
+	u32 pages_freed, total_pages_freed = 0;
+	u32 start, end, block, total_blocks_freed = 0;
 
 	if (atomic_read(&global_page_count) <= tcmu_global_max_pages)
 		return;
@@ -2949,12 +2974,14 @@ static void find_free_blocks(void)
 		unmap_mapping_range(udev->inode->i_mapping, off, 0, 1);
 
 		/* Release the block pages */
-		tcmu_blocks_release(&udev->data_pages, start, end - 1);
+		pages_freed = tcmu_blocks_release(&udev->data_pages, start, end - 1);
 		mutex_unlock(&udev->cmdr_lock);
 
-		total_freed += end - start;
-		pr_debug("Freed %u blocks (total %u) from %s.\n", end - start,
-			 total_freed, udev->name);
+		total_pages_freed += pages_freed;
+		total_blocks_freed += end - start;
+		pr_debug("Freed %u pages (total %u) from %u blocks (total %u) from %s.\n",
+			 pages_freed, total_pages_freed, end - start,
+			 total_blocks_freed, udev->name);
 	}
 	mutex_unlock(&root_udev_mutex);