Re: [PATCH] selftest: mm: Test if hugepage does not get leaked during __bio_release_pages()

[David Hildenbrand]

On 23.05.24 21:13, Andrew Morton wrote:
> On Thu, 23 May 2024 01:39:05 -0500 Donet Tom <donettom@xxxxxxxxxxxxx> wrote:
>
> > Commit 1b151e2435fc ("block: Remove special-casing of compound
> > pages") caused a change in behaviour when releasing the pages
> > if the buffer does not start at the beginning of the page. This
> > was because the calculation of the number of pages to release
> > was incorrect.
> > This was fixed by commit 38b43539d64b ("block: Fix page refcounts
> > for unaligned buffers in __bio_release_pages()").
> >
> > We pin the user buffer during direct I/O writes. If this buffer is a
> > hugepage, bio_release_page() will unpin it and decrement all references
> > and pin counts at ->bi_end_io. However, if any references to the hugepage
> > remain post-I/O, the hugepage will not be freed upon unmap, leading
> > to a memory leak.
> >
> > This patch verifies that a hugepage, used as a user buffer for DIO
> > operations, is correctly freed upon unmapping, regardless of whether
> > the offsets are aligned or unaligned w.r.t page boundary.

Two SOF, is there a Co-developed-by: missing?

> You have stable@xxxxxxxxxxxxxxx in the mail headers, so I assume you're
> proposing this for backporting.  When doing this, please include
>
> Cc: <stable@xxxxxxxxxxxxxxx>
>
> in the changelog footers and also include a Fixes: target.  I'm
> assuming the suitable Fixes: target for this patch is 38b43539d64b?

This adds a new selfest to make sure what was fixed (and backported to 
stable) remains fixed.

--
Cheers,

David / dhildenb