[PATCH v6 3/4] SCT Write Same / DSM Trim

[Shaun Tancheff <shaun@tancheff.com>]

Correct handling of devices with sector_size other that 512 bytes.

Signed-off-by: Shaun Tancheff <shaun.tancheff@seagate.com>
---
In the case of a 4Kn device sector_size it is possible to describe a much
larger DSM Trim than the current fixed default of 512 bytes.

This patch assumes the minimum descriptor is sector_size and fills out
the descriptor accordingly.

The ACS-2 specification is quite clear that the DSM command payload is
sized as number of 512 byte transfers so a 4Kn device will operate
correctly without this patch.

v5:
 - Added support for a sector_size descriptor other than 512 bytes.

 drivers/ata/libata-scsi.c | 85 +++++++++++++++++++++++++++++++----------------
 1 file changed, 57 insertions(+), 28 deletions(-)

diff --git a/drivers/ata/libata-scsi.c b/drivers/ata/libata-scsi.c
index ebf1a04..37f456e 100644
--- a/drivers/ata/libata-scsi.c
+++ b/drivers/ata/libata-scsi.c
@@ -3283,7 +3283,7 @@ static unsigned int ata_scsi_pass_thru(struct ata_queued_cmd *qc)
 /**
  * ata_format_dsm_trim_descr() - SATL Write Same to DSM Trim
  * @cmd: SCSI command being translated
- * @num: Maximum number of entries (nominally 64).
+ * @trmax: Maximum number of entries that will fit in sector_size bytes.
  * @sector: Starting sector
  * @count: Total Range of request in logical sectors
  *
@@ -3298,63 +3298,80 @@ static unsigned int ata_scsi_pass_thru(struct ata_queued_cmd *qc)
  *  LBA's should be sorted order and not overlap.
  *
  * NOTE: this is the same format as ADD LBA(S) TO NV CACHE PINNED SET
+ *
+ * Return: Number of bytes copied into sglist.
  */
-static unsigned int ata_format_dsm_trim_descr(struct scsi_cmnd *cmd, u32 num,
-					      u64 sector, u32 count)
+static size_t ata_format_dsm_trim_descr(struct scsi_cmnd *cmd, u32 trmax,
+					u64 sector, u32 count)
 {
-	__le64 *buffer;
-	u32 i = 0, used_bytes;
+	struct scsi_device *sdp = cmd->device;
+	size_t len = sdp->sector_size;
+	size_t r;
+	__le64 *buf;
+	u32 i = 0;
 	unsigned long flags;
 
-	BUILD_BUG_ON(512 > ATA_SCSI_RBUF_SIZE);
+	WARN_ON(len > ATA_SCSI_RBUF_SIZE);
+
+	if (len > ATA_SCSI_RBUF_SIZE)
+		len = ATA_SCSI_RBUF_SIZE;
 
 	spin_lock_irqsave(&ata_scsi_rbuf_lock, flags);
-	buffer = ((void *)ata_scsi_rbuf);
-	while (i < num) {
+	buf = ((void *)ata_scsi_rbuf);
+	memset(buf, 0, len);
+	while (i < trmax) {
 		u64 entry = sector |
 			((u64)(count > 0xffff ? 0xffff : count) << 48);
-		buffer[i++] = __cpu_to_le64(entry);
+		buf[i++] = __cpu_to_le64(entry);
 		if (count <= 0xffff)
 			break;
 		count -= 0xffff;
 		sector += 0xffff;
 	}
-
-	used_bytes = ALIGN(i * 8, 512);
-	memset(buffer + i, 0, used_bytes - i * 8);
-	sg_copy_from_buffer(scsi_sglist(cmd), scsi_sg_count(cmd), buffer, 512);
+	r = sg_copy_from_buffer(scsi_sglist(cmd), scsi_sg_count(cmd), buf, len);
 	spin_unlock_irqrestore(&ata_scsi_rbuf_lock, flags);
 
-	return used_bytes;
+	return r;
 }
 
 /**
  * ata_format_dsm_trim_descr() - SATL Write Same to ATA SCT Write Same
  * @cmd: SCSI command being translated
  * @lba: Starting sector
- * @num: Number of logical sectors to be zero'd.
+ * @num: Number of sectors to be zero'd.
  *
- * Rewrite the WRITE SAME descriptor to be an SCT Write Same formatted
+ * Rewrite the WRITE SAME payload to be an SCT Write Same formatted
  * descriptor.
  * NOTE: Writes a pattern (0's) in the foreground.
- *       Large write-same requents can timeout.
+ *
+ * Return: Number of bytes copied into sglist.
  */
-static void ata_format_sct_write_same(struct scsi_cmnd *cmd, u64 lba, u64 num)
+static size_t ata_format_sct_write_same(struct scsi_cmnd *cmd, u64 lba, u64 num)
 {
-	u16 *sctpg;
+	struct scsi_device *sdp = cmd->device;
+	size_t len = sdp->sector_size;
+	size_t r;
+	u16 *buf;
 	unsigned long flags;
 
 	spin_lock_irqsave(&ata_scsi_rbuf_lock, flags);
-	sctpg = ((void *)ata_scsi_rbuf);
+	buf = ((void *)ata_scsi_rbuf);
+
+	put_unaligned_le16(0x0002,  &buf[0]); /* SCT_ACT_WRITE_SAME */
+	put_unaligned_le16(0x0101,  &buf[1]); /* WRITE PTRN FG */
+	put_unaligned_le64(lba,     &buf[2]);
+	put_unaligned_le64(num,     &buf[6]);
+	put_unaligned_le32(0u,      &buf[10]); /* pattern */
+
+	WARN_ON(len > ATA_SCSI_RBUF_SIZE);
 
-	put_unaligned_le16(0x0002,  &sctpg[0]); /* SCT_ACT_WRITE_SAME */
-	put_unaligned_le16(0x0101,  &sctpg[1]); /* WRITE PTRN FG */
-	put_unaligned_le64(lba,     &sctpg[2]);
-	put_unaligned_le64(num,     &sctpg[6]);
-	put_unaligned_le32(0u,      &sctpg[10]);
+	if (len > ATA_SCSI_RBUF_SIZE)
+		len = ATA_SCSI_RBUF_SIZE;
 
-	sg_copy_from_buffer(scsi_sglist(cmd), scsi_sg_count(cmd), sctpg, 512);
+	r = sg_copy_from_buffer(scsi_sglist(cmd), scsi_sg_count(cmd), buf, len);
 	spin_unlock_irqrestore(&ata_scsi_rbuf_lock, flags);
+
+	return r;
 }
 
 /**
@@ -3371,11 +3388,13 @@ static unsigned int ata_scsi_write_same_xlat(struct ata_queued_cmd *qc)
 {
 	struct ata_taskfile *tf = &qc->tf;
 	struct scsi_cmnd *scmd = qc->scsicmd;
+	struct scsi_device *sdp = scmd->device;
+	size_t len = sdp->sector_size;
 	struct ata_device *dev = qc->dev;
 	const u8 *cdb = scmd->cmnd;
 	u64 block;
 	u32 n_block;
-	const u32 trmax = ATA_MAX_TRIM_RNUM;
+	const u32 trmax = len >> 3;
 	u32 size;
 	u16 fp;
 	u8 bp = 0xff;
@@ -3420,8 +3439,16 @@ static unsigned int ata_scsi_write_same_xlat(struct ata_queued_cmd *qc)
 	if (!scsi_sg_count(scmd))
 		goto invalid_param_len;
 
+	/*
+	 * size must match sector size in bytes
+	 * For DATA SET MANAGEMENT TRIM in ACS-2 nsect (aka count)
+	 * is defined as number of 512 byte blocks to be transferred.
+	 */
 	if (unmap) {
 		size = ata_format_dsm_trim_descr(scmd, trmax, block, n_block);
+		if (size != len)
+			goto invalid_param_len;
+
 		if (ata_ncq_enabled(dev) && ata_fpdma_dsm_supported(dev)) {
 			/* Newer devices support queued TRIM commands */
 			tf->protocol = ATA_PROT_NCQ;
@@ -3441,7 +3468,9 @@ static unsigned int ata_scsi_write_same_xlat(struct ata_queued_cmd *qc)
 			tf->command = ATA_CMD_DSM;
 		}
 	} else {
-		ata_format_sct_write_same(scmd, block, n_block);
+		size = ata_format_sct_write_same(scmd, block, n_block);
+		if (size != len)
+			goto invalid_param_len;
 
 		tf->hob_feature = 0;
 		tf->feature = 0;
-- 
2.9.3