[dm-devel] Adding/removing multi-pathed disk partitions

[Christophe Varoqui]

goggin, edward wrote:

>Should one be using the multi-path device-mapper mapped device
>name or one of the SCSI target device names for the whole disk
>device when modifying a SCSI disk's partition table with fdisk(8)?
>
>If the former, drivers/block/ioctl.c:blkdev_reread_part()
>currently returns EINVAL since the mapped device is not
>partitionable.  I can't imagine the recommendation is the
>latter, since there is no mechanism in place to synchronize
>the kernel's partition table handling amongst multiple target
>devices.
>
>--
>
As discussed earlier, one face of this problem is that kpartx does 
buffered reads to grab the on-disk partition table, leading to 
situations where kpartx ->fdisk -> kpartx sequence does not garanty 
partitons-to-maps layout will reflect reality.

To address this particular problem, do you think adding O_DIRECT to the 
open() call in kpartx.c would be enough ?

Regards,
cvaroqui