[PATCH 1/6] libata: avoid global response buffer in atapi_qc_complete

Christoph Hellwig
2017-01-10T08:41:58Z

We only need to look at 4 bytes of the inquiry response for ATAPI
devices. Instead of using the global ata_scsi_rbuf just use a
a stack buffer. Also factor the fixup into it's own little helper
function to make it more readable.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
drivers/ata/libata-scsi.c | 46 ++++++++++++++++++++++------------------------
1 file changed, 22 insertions(+), 24 deletions(-)

diff --git a/drivers/ata/libata-scsi.c b/drivers/ata/libata-scsi.c
index 1f863e7..031a77a 100644
--- a/drivers/ata/libata-scsi.c
+++ b/drivers/ata/libata-scsi.c
@@ -2873,6 +2873,26 @@ static void atapi_request_sense(struct ata_queued_cmd *qc)
DPRINTK("EXIT\n");
}

+/*
+ * ATAPI devices typically report zero for their SCSI version, and sometimes
+ * deviate from the spec WRT response data format. If SCSI version is
+ * reported as zero like normal, then we make the following fixups:
+ * 1) Fake MMC-5 version, to indicate to the Linux scsi midlayer this is a
+ * modern device.
+ * 2) Ensure response data format / ATAPI information are always correct.
+ */
+static void atapi_fixup_inquiry(struct scsi_cmnd *cmd)
+{
+ u8 buf[4];
+
+ sg_copy_to_buffer(scsi_sglist(cmd), scsi_sg_count(cmd), buf, 4);
+ if (buf[2] == 0) {
+ buf[2] = 0x5;
+ buf[3] = 0x32;
+ }
+ sg_copy_from_buffer(scsi_sglist(cmd), scsi_sg_count(cmd), buf, 4);
+}
+
static void atapi_qc_complete(struct ata_queued_cmd *qc)
{
struct scsi_cmnd *cmd = qc->scsicmd;
@@ -2927,30 +2947,8 @@ static void atapi_qc_complete(struct ata_queued_cmd *qc)
*/
ata_gen_passthru_sense(qc);
} else {
- u8 *scsicmd = cmd->cmnd;
-
- if ((scsicmd[0] == INQUIRY) && ((scsicmd[1] & 0x03) == 0)) {
- unsigned long flags;
- u8 *buf;
-
- buf = ata_scsi_rbuf_get(cmd, true, &flags);
-
- /* ATAPI devices typically report zero for their SCSI version,
- * and sometimes deviate from the spec WRT response data
- * format. If SCSI version is reported as zero like normal,
- * then we make the following fixups: 1) Fake MMC-5 version,
- * to indicate to the Linux scsi midlayer this is a modern
- * device. 2) Ensure response data format / ATAPI information
- * are always correct.
- */
- if (buf[2] == 0) {
- buf[2] = 0x5;
- buf[3] = 0x32;
- }
-
- ata_scsi_rbuf_put(cmd, true, &flags);
- }
-
+ if (cmd->cmnd[0] == INQUIRY && (cmd->cmnd[1] & 0x03) == 0)
+ atapi_fixup_inquiry(cmd);
cmd->result = SAM_STAT_GOOD;
}

--
2.1.4