On 1/7/25 10:10 AM, Anna Schumaker wrote:
Hi Takeshi,
On 1/6/25 6:56 PM, Takeshi Nishimura wrote:
Dear list,
how can we get ADB (WRITE_SAME) support in (Debian) Linux nfsd, and an
ioct() in Linux nfsd client to use it?
Thanks for the request! Just so you're aware of the process, this email list is for upstream Linux kernel development. If we decide to go ahead with adding WRITE_SAME support it'll be up to Debian later to enable it (that part is out of our hands, and isn't up to us).
We have a set of custom "big data" applications which could greatly
benefit from such an acceleration ABI, both for implementing "zero
data" (fill blocks with 0 bytes), and fill blocks with identical data
patterns, without sending the same pattern over and over again over
the network wire.
Having said that, I'm not opposed to implementing WRITE_SAME. I wonder if we could somehow use it to build support for fallocate's FALLOC_FL_ZERO_RANGE flag at the same time.
I'm also wondering if there would be any advantage to local filesystems if this were to be implemented as a generic system call, rather than as an NFS-specific ioctl(), since some storage devices have a WRITE_SAME operation that could be used for acceleration. But I haven't convinced myself either way yet.
This is a good topic for discussion at LSF!
--
Chuck Lever
