Re: [PATCH v3 09/40] docs: filesystems: update mmap_prepare docs for discontig kernel pgs

On Thu Sep 17, 2026 at 12:22 PM EDT, Lorenzo Stoakes (ARM) wrote:

Describe the newly introduced discontiguous kernel page mapping mechanism,
detailing how to use it sensibly and how the API looks.

Explicitly detail the various discontiguous actions available and how to
use them.

Signed-off-by: Lorenzo Stoakes (ARM) <ljs@kernel.org>
---
 Documentation/filesystems/mmap_prepare.rst | 81 ++++++++++++++++++++++++++++++
 1 file changed, 81 insertions(+)

<snip>

+* ``discontig_kernel_map_page()`` - Maps a single page, correctly handling
+  compound pages (if the compound page is bigger than the remaining pages in the
+  VMA, then only those pages that fit will be mapped). For a compound page, the
+  head page must be passed.
+* ``discontig_kernel_map_page_range()`` - Map an array of pages of a specified
+  size. Note that if the number of pages specified exceeds the VMA size then an
+  error will arise.

Why do mapping a compound page and a page range have different behaviors
on the bound? Either both do partial mappings or give errors when a
given input cannot be mapped as a whole in the VMA.



-- 
Best Regards,
Yan, Zi