>>>>> "Mike" == Mike Snitzer <snitzer@xxxxxxxxxx> writes: Mike> Shouldn't we also be using MAX_BIO_SECTORS in Mike> blkdev_issue_write_same (instead of UINT_MAX >> 9)? The granularity of WRITE SAME is always 1 logical block and there is no reason to round it down to the next power of two. +/* + * Ensure that max discard sectors doesn't overflow bi_size and hopefully + * it is of the proper granularity as long as the granularity is a power + * of two. + */ +#define MAX_DISCARD_SECTORS ((1U << 31) >> 9) + That's fine for SATA since we're already capping at 2TB minus change. But it means we'll be capping unnecessarily on SCSI. And larger range counts are impending in SATA as well. So this goes back to my original comment: The only place there can be a discard granularity is for SCSI UNMAP. And consequently, we should only enforce alignment and granularity when that code path is taken in sd.c. I'm OK with Ming's patch series in general. Let's leave the discard cap at UINT_MAX and I'll twiddle the rest in SCSI. Reviewed-by: Martin K. Petersen <martin.petersen@xxxxxxxxxx> -- Martin K. Petersen Oracle Linux Engineering -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
