On Tue, Oct 13, 2020 at 12:25:44PM +0100, Christoph Hellwig wrote:

...

• kaddr = kmap(pp);

• kaddr = kmap_thread(pp); memcpy(kaddr, vip->vii_immed.vi_immed + offset, PAGE_SIZE);

• kunmap(pp);

• kunmap_thread(pp);

You only Cced me on this particular patch, which means I have absolutely no idea what kmap_thread and kunmap_thread actually do, and thus can't provide an informed review.

Sorry the list was so big I struggled with who to CC and on which patches.

That being said I think your life would be a lot easier if you add helpers for the above code sequence and its counterpart that copies to a potential hughmem page first, as that hides the implementation details from most users.

Matthew Wilcox and Al Viro have suggested similar ideas.

https://lore.kernel.org/lkml/20201013205012.GI2046448@iweiny-DESK2.sc.intel....

Ira