[PATCHv3 02/11] drm/i915/gem: Convert __shmem_writeback() to folios

[Matthew Wilcox]

On Thu, Jan 30, 2025 at 12:00:40PM +0200, Kirill A. Shutemov wrote:
> Use folios instead of pages.
> 
> This is preparation for removing PG_reclaim.

Well, this is a horrid little function.  Rather than iterating just the
dirty folios, it iterates all folios, then locks them before checking
whether they're dirty.

I don't know whether the comments are correct or the code is correct.
This comment doesn't match with setting PageReclaim:

         * Leave mmapings intact (GTT will have been revoked on unbinding,
         * leaving only CPU mmapings around) and add those pages to the LRU
         * instead of invoking writeback so they are aged and paged out
         * as normal.

so I wonder if Chris was confused about what PageReclaim actually does.
Let's find out if he still remembers what he thought it did!