Re: [PATCH 1/2] mm/shmem: add shmem_backup_folio() helper

[Christoph Hellwig]

On Tue, Jul 21, 2026 at 10:47:22AM -0700, Matthew Brost wrote:
> Add a new generic helper, shmem_backup_folio(), that copies the pages
> of an arbitrary source folio into a range of a shmem-backed file,
> optionally issuing writeback for each destination folio. It is
> extracted from drivers/gpu/drm/ttm's existing shmem-backup loop so
> that other subsystems (starting with TTM in a follow-up patch) can
> share the same implementation.

Hmm, what is the difference to just doing a ITER_BVEC write with a bvec
containing the folio for this the pure write to shmem part of this?

You'd probably want a kernel_write_iter helper wrapping
__kernel_write_iter for the writecount, but otherwise this sounds
like a normal write.

We'd want something for the writeback part, preferably a purely
range based API to be generic.