On Mon, 19 Feb 2007, Douglas Gilbert wrote: > > Come to think of it, the reserved_size value used when a new sg device is > > created should also be capped at max_sectors * 512. Agreed? I can't see > > any reason for ever having a larger buffer -- it would be impossible to > > make use of the extra space. > > Alan, > That depends whether or not max_sectors can be changed > (via sysfs) subsequent to a sg device being created. > And I think it can. > > # ls -l /sys/block/sdc/queue/ > total 0 > drwxr-xr-x 2 root root 0 Feb 19 18:29 iosched > -r--r--r-- 1 root root 4096 Feb 19 23:41 max_hw_sectors_kb > -rw-r--r-- 1 root root 4096 Feb 19 23:41 max_sectors_kb > -rw-r--r-- 1 root root 4096 Feb 19 23:41 nr_requests > -rw-r--r-- 1 root root 4096 Feb 19 23:41 read_ahead_kb > -rw-r--r-- 1 root root 4096 Feb 19 23:41 scheduler
Yes, it definitely can be changed. > # cat max_hw_sectors_kb > max_sectors_kb > > ... is the real maximum if the LLD that set max_hw_sectors_kb > is to be believed (actually it is often a finger in > the wind). That's why my patch computes the minimum value every time the GET_RESERVED_SIZE ioctl runs -- in case max_sectors has changed. If the user decides to increase max_sectors, then the reserved_size can be increased immediately afterward. This shouldn't cause any problems. I will submit a revised patch shortly, on the linux-scsi list. Alan Stern - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
