From: Andrew Morton <akpm@linux-foundation.org>
To: Peter Xu <peterx@redhat.com>
Cc: Matthew Wilcox <willy@infradead.org>,
"Vishal Moola (Oracle)" <vishal.moola@gmail.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
linux-fsdevel@vger.kernel.org, Hugh Dickins <hughd@google.com>,
Axel Rasmussen <axelrasmussen@google.com>
Subject: Re: [PATCH 3/5] userfualtfd: Replace lru_cache functions with folio_add functions
Date: Wed, 2 Nov 2022 13:47:14 -0700 [thread overview]
Message-ID: <20221102134714.c72bea3c997ba3ef90d72c53@linux-foundation.org> (raw)
In-Reply-To: <Y2K+y7wnhC4vbnP2@x1n>
On Wed, 2 Nov 2022 15:02:35 -0400 Peter Xu <peterx@redhat.com> wrote:
> mfill_atomic_install_pte() checks page->mapping to detect whether one page
> is used in the page cache. However as pointed out by Matthew, the page can
> logically be a tail page rather than always the head in the case of uffd
> minor mode with UFFDIO_CONTINUE. It means we could wrongly install one pte
> with shmem thp tail page assuming it's an anonymous page.
>
> It's not that clear even for anonymous page, since normally anonymous pages
> also have page->mapping being setup with the anon vma. It's safe here only
> because the only such caller to mfill_atomic_install_pte() is always
> passing in a newly allocated page (mcopy_atomic_pte()), whose page->mapping
> is not yet setup. However that's not extremely obvious either.
>
> For either of above, use page_mapping() instead.
>
> And this should be stable material.
I added
Fixes: 153132571f02 ("userfaultfd/shmem: support UFFDIO_CONTINUE for shmem")
next prev parent reply other threads:[~2022-11-02 20:47 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-11-01 17:53 [PATCH 0/5] Removing the lru_cache_add() wrapper Vishal Moola (Oracle)
2022-11-01 17:53 ` [PATCH 1/5] filemap: Convert replace_page_cache_page() to replace_page_cache_folio() Vishal Moola (Oracle)
2022-11-01 18:20 ` Matthew Wilcox
2022-11-01 17:53 ` [PATCH 2/5] fuse: Convert fuse_try_move_page() to use folios Vishal Moola (Oracle)
2022-11-01 18:24 ` Matthew Wilcox
2022-11-10 18:36 ` Vishal Moola
2022-11-14 13:25 ` Miklos Szeredi
2022-11-01 17:53 ` [PATCH 3/5] userfualtfd: Replace lru_cache functions with folio_add functions Vishal Moola (Oracle)
2022-11-01 18:31 ` Matthew Wilcox
2022-11-02 19:02 ` Peter Xu
2022-11-02 19:21 ` Matthew Wilcox
2022-11-02 20:44 ` Peter Xu
2022-11-03 17:34 ` Axel Rasmussen
2022-11-03 17:56 ` Peter Xu
2022-11-02 20:47 ` Andrew Morton [this message]
2022-11-01 17:53 ` [PATCH 4/5] khugepage: Replace lru_cache_add() with folio_add_lru() Vishal Moola (Oracle)
2022-11-01 18:32 ` Matthew Wilcox
2022-11-01 17:53 ` [PATCH 5/5] folio-compat: Remove lru_cache_add() Vishal Moola (Oracle)
2022-11-01 18:33 ` Matthew Wilcox
2022-11-29 19:25 ` [PATCH 0/5] Removing the lru_cache_add() wrapper Vishal Moola
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