Re: [PATCH v3] page cache: Store only head pages in i_pages

[William Kucharski <william.kucharski@oracle.com>]

Other than the bug Song found in memfd_tag_pins(), I'd like to suggest two quick
but pedantic changes to mm/filemap.c:

Though not modified in this patch, in line 284, the parenthesis should be moved
to after the period:

 * modified.) The function expects only THP head pages to be present in the

> +		 * Move to the next page in the vector if this is a small page
> +		 * or the index is of the last page in this compound page).

A few lines later, there is an extraneous parenthesis, and the comment could be a bit
clearer.

Might I suggest:

                 * Move to the next page in the vector if this is a PAGESIZE
                 * page or if the index is of the last PAGESIZE page within
                 * this compound page.

You can say "base" instead of "PAGESIZE," but "small" seems open to interpretation.

I haven't run across any problems and have been hammering the code for over five days
without issue; all my testing was with transparent_hugepage/enabled set to
"always."

Tested-by: William Kucharski <william.kucharski@oracle.com>
Reviewed-by: William Kucharski <william.kucharski@oracle.com>