Merge patch series "iomap: erofs page cache sharing preliminaries"

Bring in the two changes needed in iomap and erofs to enable the page
cache sharing work.

* patches from https://patch.msgid.link/20260109102856.598531-1-lihongbo22@huawei.com:
  erofs: hold read context in iomap_iter if needed
  iomap: stash iomap read ctx in the private field of iomap_iter

Link: https://patch.msgid.link/20260109102856.598531-1-lihongbo22@huawei.com
Signed-off-by: Christian Brauner <brauner@kernel.org>