On Thu, Jun 17, 2010 at 10:10:18AM +0200, Jens Axboe wrote: > Thanks, applied. There was a recent problem report on btrfs using > discard, could possibly explain it if Chris assumed it was a full > barrier. We actually have a much bigger issue with the DISCARD_BARRIER type. If the discard request needs to get split into multiple smaller ones we don't keep the queue drained atomically around them, so requests could sneak inbetween them. Depending on how the realtime discard is implemented that could cause issues. In my XFS prototype for it I only deleted the extents from the tracking betree after the discard request has returned, but other filesystems rely on full barrier semantics of DISCARD_BARRIER this could cause real problems. -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
