Re: [PATCH] mm: don't convert the page to folio before splitting in split_huge_page()

[Christian Brauner <brauner@kernel.org>]

On Mon, Sep 02, 2024 at 03:00:37PM GMT, Matthew Wilcox wrote:
> On Mon, Sep 02, 2024 at 02:49:32PM +0200, Pankaj Raghav (Samsung) wrote:
> > From: Pankaj Raghav <p.raghav@samsung.com>
> > 
> > Sven reported that a commit from bs > ps series was breaking the ksm ltp
> > test[1].
> > 
> > split_huge_page() takes precisely a page that is locked, and it also
> > expects the folio that contains that page to be locked after that
> > huge page has been split. The changes introduced converted the page to
> > folio, and passed the head page to be split, which might not be locked,
> > resulting in a kernel panic.
> > 
> > This commit fixes it by always passing the correct page to be split from
> > split_huge_page() with the appropriate minimum order for splitting.
> 
> This should be folded into the patch that is broken, not be a separate
> fix commit, otherwise it introduces a bisection hazard which are to be
> avoided when possible.

Patch folded into "mm: split a folio in minimum folio order chunks"
with the Link to this patch. Please double-check.