On Sat, Aug 09 2008, David Woodhouse wrote: > This time on top of the for-2.6.28 branch of > git://git.kernel.dk/linux-2.6-block.git > > I've made it cope with merging and sorting discard requests, still as a > separate patch at the end of the sequence. I don't think we have a > problem with discards passing writes in the queue, any more than we > _already_ had a problem with writes passing writes. But we don't already have this problem, that is the point. For page cache writes, the page cache nicely solves this issue for us - a write that comes in later gets to wait on the page lock before proceeding. So at least it's ordered. For O_DIRECT, the issuer is on his own. I think this is a serious problem and that we must ensure that an overlapping write doesn't pass a previously issued discard request. So in that sense, discards must be considered soft barriers. -- Jens Axboe -- 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
