Re: [PATCH] SG: cap reserved_size values at max_sectors

[Mike Christie <michaelc@cs.wisc.edu>]

Mike Christie wrote:
> 
> The problem is that we assume we will get nice large segments. When
> using sg it will try to allocate multiple pages and make large segments.
> We could hit a bad case where we cannot allocate enough large segments,
> so a worst case would result in a max_segment_size of PAGE_SIZE:
> 
> max_segments = min(q->max_hw_segments, q->max_phys_segments);
> 
> max_xfer = min(q->max_hw_sectors * 512,
> 		max_segments * PAGE_SIZE);
> 
> return max_xfer;
> 
Oh yeah, you could also check how large the reserved buffer is already.
The estimate above does not take into account if we had already
allocated a nice large reserved buffer with large segments.