Re: [LSF/MM/BPF TOPIC] selectively cramming things onto struct bio

["Theodore Y. Ts'o" <tytso@mit.edu>]

On Thu, Jan 30, 2020 at 04:44:47PM -0800, Darrick J. Wong wrote:
> Hi everyone,
> 
> Several months ago, there was a discussion[1] about enhancing XFS to
> take a more active role in recoverying damaged blocks from a redundant
> storage device when the block device doesn't signal an error but the
> filesystem can tell that something is wrong.
> 
> Yes, we (XFS) would like to be able to exhaust all available storage
> redundancy before we resort to rebuilding lost metadata, and we'd like
> to do that without implementing our own RAID layer.
> 
> In the end, the largest stumbling block seems to be how to attach
> additional instructions to struct bio.  Jens rejected the idea of adding
> more pointers or more bytes to a struct bio since we'd be forcing
> everyone to pay the extra memory price for a feature that in the ideal
> situation will be used infrequently.

I'd be interested in this discussion as well; the issue came up when
adding support for hardware-based inline-crypto support.

							- Ted