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    Subject[PATCH 5.4 045/191] scsi: tracing: Fix handling of TRANSFER LENGTH == 0 for READ(6) and WRITE(6)
    Date
    From: Bart Van Assche <bvanassche@acm.org>

    [ Upstream commit f6b8540f40201bff91062dd64db8e29e4ddaaa9d ]

    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>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    drivers/scsi/scsi_trace.c | 11 +++++++----
    1 file changed, 7 insertions(+), 4 deletions(-)

    diff --git a/drivers/scsi/scsi_trace.c b/drivers/scsi/scsi_trace.c
    index 0f17e7dac1b0..07a2425ffa2c 100644
    --- a/drivers/scsi/scsi_trace.c
    +++ b/drivers/scsi/scsi_trace.c
    @@ -18,15 +18,18 @@ static const char *
    scsi_trace_rw6(struct trace_seq *p, unsigned char *cdb, int len)
    {
    const char *ret = trace_seq_buffer_ptr(p);
    - 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;
    --
    2.20.1


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