On Wed, 2015-09-30 at 09:08 -0700, Christoph Hellwig wrote:
> Hi all,
>
> I'd like to propose the following patch intead. It uses a helper
> to check the conditions for the copied commands, and also fixes another
> place to use it which uses a different and I think buggy check:
>
> This avoids the usage of scsi_cmnd.SCp which I'd like to get rid of
> mid-term.
>
> diff --git a/drivers/scsi/3w-9xxx.c b/drivers/scsi/3w-9xxx.c
> index add419d..74eac90 100644
> --- a/drivers/scsi/3w-9xxx.c
> +++ b/drivers/scsi/3w-9xxx.c
> @@ -212,6 +212,17 @@ static const struct file_operations twa_fops = {
> .llseek = noop_llseek,
> };
>
> +/*
> + * The controllers use an inline buffer instead of a mapped SGL for small,
> + * single entry buffers. Note that we treat a zero-length transfer like
> + * a mapped SGL.
> + */
> +static bool twa_command_mapped(struct scsi_cmnd *cmd)
> +{
> + return scsi_sg_count(cmd) != 1 ||
> + scsi_bufflen(cmd) >= TW_MIN_SGL_LENGTH;
> +}
I already thought of this. Unfortunately, it fails if the internally
posted command is a single sector (the size of TW_MIN_SGL_LENGTH), which
is true for most of them.
James
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