Page MenuHomeFreeBSD
Differential D58762

linuxkpi: Add `split_page()`
ClosedPublic
Actions

Authored by dumbbell on Aug 10 2026, 5:31 PM.
Tags
Referenced Files
F174550747: D58762.id185651.diff
Sun, Oct 4, 2:43 AM
F174521530: D58762.id186158.diff
Sat, Oct 3, 9:43 PM
F174513038: D58762.diff
Sat, Oct 3, 8:20 PM
Unknown Object (File)
Sat, Oct 3, 10:38 AM
Unknown Object (File)
Fri, Oct 2, 10:41 PM
Unknown Object (File)
Fri, Oct 2, 10:37 PM
Unknown Object (File)
Fri, Oct 2, 6:15 PM
Unknown Object (File)
Thu, Oct 1, 3:43 PM
View All 62 Files
Subscribers
bz
emaste
imp

Details

Reviewers
bz
Group Reviewers
linuxkpi
Commits
rG153446ecd740: linuxkpi: Add `split_page()`
Summary

This function is supposed to split large pages into an array of PAGE_SIZE-sized pages, with correct refcounting. This is apparently used to allow some drivers to free a part of a large page only.

I don't think we use large pages in linuxkpi. Therefore, this new function is curently a no-op.

The DRM drivers TTM memory manager started to use it in Linux 6.15.

Sponsored by: The FreeBSD Foundation

Diff Detail

Repository
rG FreeBSD src repository
Lint
Lint Skipped
Unit
Tests Skipped

Event Timeline

dumbbell created this revision.Aug 10 2026, 5:31 PM
Herald added subscribers: emaste, imp. · View Herald TranscriptAug 10 2026, 5:31 PM
dumbbell requested review of this revision.Aug 10 2026, 5:31 PM
emaste added a comment.Aug 10 2026, 5:32 PM

I don't think we use large pages in linuxkpi. Therefore, this new function is curently a no-op.

Is there a way we can add either a compile-time error or KASSERT to ensure this remains the case?

dumbbell added a parent revision: D58761: linuxkpi: Include <linux/page-flags.h> from <linux/mm.h>.Aug 10 2026, 5:34 PM
dumbbell added a child revision: D58763: linuxkpi: Add several folio-related functions.
bz added a subscriber: bz.Aug 10 2026, 6:32 PM
In D58762#1348310, @emaste wrote:

I don't think we use large pages in linuxkpi. Therefore, this new function is curently a no-op.

Is there a way we can add either a compile-time error or KASSERT to ensure this remains the case?

Or at least at the pr_debug("%s:TODO\n", func). I really should make that a macro and replace all occurrences.

emaste added a project: linuxkpi.Aug 17 2026, 4:58 PM
dumbbell updated this revision to Diff 185651.Sep 2 2026, 9:04 PM

Add a TODO.

I did’t find an API to get the size of a page, so I’m not sure how to implement an assertion.

bz added a comment.Sep 2 2026, 9:45 PM

You'll likely have to make ttm_pool_split_for_swap() return early then in FreeBSD?

bz accepted this revision.Sep 2 2026, 9:45 PM
This revision is now accepted and ready to land.Sep 2 2026, 9:45 PM
Closed by commit rG153446ecd740: linuxkpi: Add `split_page()` (authored by dumbbell). · Explain WhyMon, Sep 7, 6:37 PM
This revision was automatically updated to reflect the committed changes.
dumbbell added a commit: rG153446ecd740: linuxkpi: Add `split_page()`.

Revision Contents
Changeset List

PathSize
sys/
compat/
linuxkpi/
common/
include/
linux/
6 lines

Diff 185651

View Options

sys/compat/linuxkpi/common/include/linux/mm.h

Loading...