On Thu, Jul 26, 2012 at 10:12 PM, Boaz Harrosh <bharrosh@xxxxxxxxxxx> wrote: > There is an easy locking solution for DIO which will not cost much > for DIO and will cost nothing for buffered IO. You use the page-cache > page lock. > > What you do is grab the zero-page of each block lock before/during writing to > any block. So for your example above they will all be serialized by page-zero > lock. Yeah, I agree this can work. But I'd prefer not to mix DIO with buffer IO, which is often error prone. If in any case I need to serialize AIODIO, I'd prefer to do it in easier ways like locking invalid extents etc, without messing with page cache. > > Of course you need like before to flush the page-cache pages before DIO and > invalidate all pages (NotUpToDate). You keep at least one page in page-cache > per block, but during DIO it will always be in Not-Up-To-Date empty state. > > Then if needed, like example above the first time COW you still do through > page-cache > > * > * That said I think your solution for only allowing BLOCK aligned DIO is good > * Applications should learn. They should however find out what BLOCK size is. > * > > You could keep the proper info at the DM device you create for each device_id > See here: http://people.redhat.com/msnitzer/docs/io-limits.txt > The "logical_block_size" should be the proper BLOCK size above. > Or maybe somehow through statfs(2), since the blocksize attribute is actually a file system's attribute instead of block device's. -- Thanks, Tao -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
