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

[Christophe Varoqui <christophe varoqui free fr>]

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