linux-kernel - Re: [PATCH 6.3.y] mm/hugetlb: revert use of page_cache_next

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Message-ID: <2023070356-paddling-grip-b31a@gregkh>
Date:   Mon, 3 Jul 2023 20:31:06 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Sidhartha Kumar <sidhartha.kumar@...cle.com>
Cc:     stable@...r.kernel.org, linux-kernel@...r.kernel.org,
        songmuchun@...edance.com, mike.kravetz@...cle.com,
        Ackerley Tng <ackerleytng@...gle.com>
Subject: Re: [PATCH 6.3.y] mm/hugetlb: revert use of page_cache_next_miss()

On Thu, Jun 29, 2023 at 05:18:17PM -0400, Sidhartha Kumar wrote:
> commit fd4aed8d985a3236d0877ff6d0c80ad39d4ce81a upstream
> 
> Ackerley Tng reported an issue with hugetlbfs fallocate as noted in the
> Closes tag.  The issue showed up after the conversion of hugetlb page
> cache lookup code to use page_cache_next_miss.  User visible effects are:
> 
> - hugetlbfs fallocate incorrectly returns -EEXIST if pages are presnet
>   in the file.
> - hugetlb pages will not be included in core dumps if they need to be
>   brought in via GUP.
> - userfaultfd UFFDIO_COPY will not notice pages already present in the
>   cache.  It may try to allocate a new page and potentially return
>   ENOMEM as opposed to EEXIST.
> 
> Revert the use page_cache_next_miss() in hugetlb code.
> 
> The upstream fix[2] cannot be used used directly as the return value for
> filemap_get_folio() has been changed between 6.3 and upstream.
> 
> Closes: https://lore.kernel.org/linux-mm/cover.1683069252.git.ackerleytng@google.com
> Fixes: d0ce0e47b323 ("mm/hugetlb: convert hugetlb fault paths to use alloc_hugetlb_folio()")
> Cc: <stable@...r.kernel.org> #v6.3
> Reported-by: Ackerley Tng <ackerleytng@...gle.com>
> Signed-off-by: Sidhartha Kumar <sidhartha.kumar@...cle.com>
> 
> [1] https://lore.kernel.org/linux-mm/cover.1683069252.git.ackerleytng@google.com/
> [2] https://lore.kernel.org/lkml/20230621230255.GD4155@monkey/
> ---
> 
>  fs/hugetlbfs/inode.c |  8 +++-----
>  mm/hugetlb.c         | 11 +++++------
>  2 files changed, 8 insertions(+), 11 deletions(-)

Now queued up, thanks.

greg k-h