>>>>> "Malahal" == malahal <malahal@xxxxxxxxxx> writes: >> 1. lock the buffers and unmap the pages while they are being >> written. --- upstream developers would likely reject it. No other >> driver than dm-raid1 has problems with this and they wouldn't damp >> performance because of one driver. 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. So this problem is not specific to DM/MD... -- Martin K. Petersen Oracle Linux Engineering -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
