[$] Improving iov_iter

The iov_iter interface is used to
describe and iterate through buffers in the kernel. David Howells led a combined storage and
filesystem session at
the 2025 Linux Storage,
Filesystem, Memory Management, and BPF Summit (LSFMM+BPF) to discuss ways
to improve iov_iter. His topic
proposal listed a few different ideas including replacing some
iov_iter types and possibly allowing mixed types in chains of iov_iter
entries; he would like to make the interface itself and the uses of iov_iter in
the kernel better.