From: Peter Xu <peterx@redhat.com>
To: Suren Baghdasaryan <surenb@google.com>
Cc: akpm@linux-foundation.org, viro@zeniv.linux.org.uk,
brauner@kernel.org, shuah@kernel.org, aarcange@redhat.com,
lokeshgidra@google.com, david@redhat.com, ryan.roberts@arm.com,
hughd@google.com, mhocko@suse.com, axelrasmussen@google.com,
rppt@kernel.org, willy@infradead.org, Liam.Howlett@oracle.com,
jannh@google.com, zhangpeng362@huawei.com, bgeffon@google.com,
kaleshsingh@google.com, ngeoffray@google.com, jdduke@google.com,
linux-mm@kvack.org, linux-fsdevel@vger.kernel.org,
linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org,
kernel-team@android.com
Subject: Re: [PATCH 1/1] userfaultfd: fix move_pages_pte() splitting folio under RCU read lock
Date: Tue, 2 Jan 2024 16:59:56 +0800 [thread overview]
Message-ID: <ZZPQjO91fvB66z1s@x1n> (raw)
In-Reply-To: <20231230025607.2476912-1-surenb@google.com>
On Fri, Dec 29, 2023 at 06:56:07PM -0800, Suren Baghdasaryan wrote:
> @@ -1078,9 +1078,14 @@ static int move_pages_pte(struct mm_struct *mm, pmd_t *dst_pmd, pmd_t *src_pmd,
>
> /* at this point we have src_folio locked */
> if (folio_test_large(src_folio)) {
> + /* split_folio() can block */
> + pte_unmap(&orig_src_pte);
> + pte_unmap(&orig_dst_pte);
> + src_pte = dst_pte = NULL;
> err = split_folio(src_folio);
> if (err)
> goto out;
> + goto retry;
> }
Do we also need to clear src_folio and src_folio_pte? If the folio is a
thp, I think it means it's pte mapped here. Then after the split we may
want to fetch the small folio after the split, not the head one?
--
Peter Xu
next prev parent reply other threads:[~2024-01-02 9:00 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-12-30 2:56 Suren Baghdasaryan
2024-01-02 8:59 ` Peter Xu [this message]
2024-01-02 16:58 ` Suren Baghdasaryan
2024-01-02 23:16 ` Suren Baghdasaryan
2024-01-02 23:34 ` Suren Baghdasaryan
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