From: Matthew Wilcox <willy@infradead.org>
To: Lokesh Gidra <lokeshgidra@google.com>
Cc: akpm@linux-foundation.org, linux-mm@kvack.org,
linux-kernel@vger.kernel.org, surenb@google.com,
kernel-team@android.com, aarcange@redhat.com, peterx@redhat.com,
david@redhat.com, zhengqi.arch@bytedance.com,
kaleshsingh@google.com, ngeoffray@google.com
Subject: Re: [PATCH] userfaultfd: change src_folio after ensuring it's unpinned in UFFDIO_MOVE
Date: Thu, 4 Apr 2024 18:21:50 +0100 [thread overview]
Message-ID: <Zg7hrt5HudXLBUn_@casper.infradead.org> (raw)
In-Reply-To: <20240404171726.2302435-1-lokeshgidra@google.com>
On Thu, Apr 04, 2024 at 10:17:26AM -0700, Lokesh Gidra wrote:
> - folio_move_anon_rmap(src_folio, dst_vma);
> - WRITE_ONCE(src_folio->index, linear_page_index(dst_vma, dst_addr));
> -
> src_pmdval = pmdp_huge_clear_flush(src_vma, src_addr, src_pmd);
> /* Folio got pinned from under us. Put it back and fail the move. */
> if (folio_maybe_dma_pinned(src_folio)) {
> @@ -2270,6 +2267,9 @@ int move_pages_huge_pmd(struct mm_struct *mm, pmd_t *dst_pmd, pmd_t *src_pmd, pm
> goto unlock_ptls;
> }
>
> + folio_move_anon_rmap(src_folio, dst_vma);
> + WRITE_ONCE(src_folio->index, linear_page_index(dst_vma, dst_addr));
> +
This use of WRITE_ONCE scares me. We hold the folio locked. Why do
we need to use WRITE_ONCE? Who's looking at folio->index without
holding the folio lock?
next prev parent reply other threads:[~2024-04-04 17:21 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-04 17:17 Lokesh Gidra
2024-04-04 17:21 ` Matthew Wilcox [this message]
2024-04-04 20:07 ` Suren Baghdasaryan
[not found] ` <adce9a6f-fccf-4c9b-8ca3-3140a6a3d326@redhat.com>
2024-04-04 20:23 ` Suren Baghdasaryan
2024-04-04 20:37 ` Andrew Morton
2024-04-04 20:32 ` Peter Xu
2024-04-04 20:55 ` Suren Baghdasaryan
2024-04-04 21:04 ` Peter Xu
2024-04-04 21:07 ` Suren Baghdasaryan
2024-04-10 17:09 ` Peter Xu
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=Zg7hrt5HudXLBUn_@casper.infradead.org \
--to=willy@infradead.org \
--cc=aarcange@redhat.com \
--cc=akpm@linux-foundation.org \
--cc=david@redhat.com \
--cc=kaleshsingh@google.com \
--cc=kernel-team@android.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=lokeshgidra@google.com \
--cc=ngeoffray@google.com \
--cc=peterx@redhat.com \
--cc=surenb@google.com \
--cc=zhengqi.arch@bytedance.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox