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Subject[PATCH 3.16 057/148] scsi: tracing: Fix handling of TRANSFER LENGTH == 0 for READ(6) and WRITE(6)
3.16.82-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Bart Van Assche <bvanassche@acm.org>

commit f6b8540f40201bff91062dd64db8e29e4ddaaa9d upstream.

According to SBC-2 a TRANSFER LENGTH field of zero means that 256 logical
blocks must be transferred. Make the SCSI tracing code follow SBC-2.

Fixes: bf8162354233 ("[SCSI] add scsi trace core functions and put trace points")
Cc: Christoph Hellwig <hch@lst.de>
Cc: Hannes Reinecke <hare@suse.com>
Cc: Douglas Gilbert <dgilbert@interlog.com>
Link: https://lore.kernel.org/r/20191105215553.185018-1-bvanassche@acm.org
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
drivers/scsi/scsi_trace.c | 11 +++++++----
1 file changed, 7 insertions(+), 4 deletions(-)

--- a/drivers/scsi/scsi_trace.c
+++ b/drivers/scsi/scsi_trace.c
@@ -30,15 +30,18 @@ static const char *
scsi_trace_rw6(struct trace_seq *p, unsigned char *cdb, int len)
{
const char *ret = p->buffer + p->len;
- sector_t lba = 0, txlen = 0;
+ u32 lba = 0, txlen;

lba |= ((cdb[1] & 0x1F) << 16);
lba |= (cdb[2] << 8);
lba |= cdb[3];
- txlen = cdb[4];
+ /*
+ * From SBC-2: a TRANSFER LENGTH field set to zero specifies that 256
+ * logical blocks shall be read (READ(6)) or written (WRITE(6)).
+ */
+ txlen = cdb[4] ? cdb[4] : 256;

- trace_seq_printf(p, "lba=%llu txlen=%llu",
- (unsigned long long)lba, (unsigned long long)txlen);
+ trace_seq_printf(p, "lba=%u txlen=%u", lba, txlen);
trace_seq_putc(p, 0);

return ret;
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