Re: [PATCH RFC] increase ST_MAX_TAPES from 128 to 1024

[James Bottomley <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx>]

On Fri, 2012-08-17 at 10:50 -0400, Rob Evers wrote:
> Wondering if this would be an acceptable interim solution
> to increasing the limit on the number of tape drives
> while http://marc.info/?l=linux-scsi&m=134212042809524&w=2
> gets sorted out.
> 
> Signed-off-by: Rob Evers <revers@xxxxxxxxxx>
> ---
>  drivers/scsi/st.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/scsi/st.h b/drivers/scsi/st.h
> index b548923..408d24f 100644
> --- a/drivers/scsi/st.h
> +++ b/drivers/scsi/st.h
> @@ -76,7 +76,7 @@ struct st_modedef {
>  #define ST_MODE_SHIFT (7 - ST_NBR_MODE_BITS)
>  #define ST_MODE_MASK ((ST_NBR_MODES - 1) << ST_MODE_SHIFT)
>  
> -#define ST_MAX_TAPES 128
> +#define ST_MAX_TAPES 1024

This is going to cause an order 2 GFP_ATOMIC allocation (on 64 bit
platforms) for the contiguous scsi_tapes array ... if large numbers of
tapes are genuinely required, shouldn't we fix this first and then
expand the number quite a bit more?

James


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