Martin K. Petersen [mkp@xxxxxxx] wrote: > >>>>> "Malahal" == malahal <malahal@xxxxxxxxxx> writes: > > [I sent this last week but it never made it to the list] > > Malahal> Very few drivers require it, so how about an interface to > Malahal> lock the pages of an I/O available to drivers. Only needed > Malahal> RAID drivers would lock the I/O while it is in progress and > Malahal> they only pay the performance penalty. mmap pages are a bit > Malahal> tricky. They need to go into read-only mode when an I/O is in > Malahal> progress. I know this would likely be rejected too!!! > > I have exactly the same problem with the data integrity stuff I'm > working on. > > Essentially a checksum gets generated when a bio is submitted, and > both the I/O controller and the disk drive verify the checksum. > > With ext2 in particular I often experience that the page (usually > containing directory metadata) has been modified before the controller > does the DMA. And the I/O will then be rejected by the controller or > drive because the checksum doesn't match the data. Your problem is very similar to an iSCSI problem sumitted here: http://now.netapp.com/NOW/cgi-bin/bol?Type=Detail&Display=137902 Fortunately, you can detect the problem and the I/O can be retried if possible. In the RAID case, it goes undetected until you hit the eventual corruption! -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
