[dm-devel] [PATCH 0/2] block: blk_interposer v3

[Bart Van Assche]

On 1/28/21 9:12 AM, Sergei Shtepa wrote:
> I`m ready to suggest the blk_interposer again.
> blk_interposer allows to intercept bio requests, remap bio to
> another devices or add new bios.
> 
> This version has support from device mapper.
> 
> For the dm-linear device creation command, the `noexcl` parameter
> has been added, which allows to open block devices without
> FMODE_EXCL mode. It allows to create dm-linear device on a block
> device with an already mounted file system.
> The new ioctl DM_DEV_REMAP allows to enable and disable bio
> interception.
> 
> Thus, it is possible to add the dm-device to the block layer stack
> without reconfiguring and rebooting.

What functionality does this driver provide that is not yet available in 
a RAID level 1 (mirroring) driver + a custom dm driver? My understanding 
is that there are already two RAID level 1 drivers in the kernel tree 
and that both driver support sending bio's to two different block devices.

Thanks,

Bart.