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Differential D58762

linuxkpi: Add `split_page()`
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Authored by dumbbell on Mon, Aug 10, 5:31 PM.
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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

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Event Timeline

dumbbell created this revision.Mon, Aug 10, 5:31 PM
Herald added subscribers: emaste, imp. · View Herald TranscriptMon, Aug 10, 5:31 PM
dumbbell requested review of this revision.Mon, Aug 10, 5:31 PM
emaste added a comment.Mon, Aug 10, 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>.Mon, Aug 10, 5:34 PM
dumbbell added a child revision: D58763: linuxkpi: Add several folio-related functions.
bz added a subscriber: bz.Mon, Aug 10, 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.Mon, Aug 17, 4:58 PM
dumbbell updated this revision to Diff 185651.Wed, Sep 2, 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.Wed, Sep 2, 9:45 PM

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

bz accepted this revision.Wed, Sep 2, 9:45 PM
This revision is now accepted and ready to land.Wed, Sep 2, 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()`.

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

Diff 186158

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

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