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charset=utf-8 Content-Disposition: inline X-Rspamd-Queue-Id: A0BA618000A X-Rspam-User: X-Rspamd-Server: rspam02 X-Stat-Signature: rydz66wrbwdidcebpmkae3ntd7bntsi9 X-HE-Tag: 1709774442-911284 X-HE-Meta: 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 FyqqaPnP SLo7cKtyTzCwkDJ2/X7P+cRsBWZvxGxCHYThrZc3BXiMZCvMfsZiQS0Csv02tfO0l5ZYUMdYx0QzditUN2lN5jMpK7gASK5HGQKt91BCVra3qZA2ZomxTEuBT6NQGEwdXB/RdJgkCtUgLqd0q0NFhfJZz0DKKyUi0F6e0xVY9Ud/cH0aKZ5xgWi2iaeG+RCiTNWg9jtQx6eGzQ+ZqAEi5S2Z5r31du6ecx1ds5BOTiaLdw34DhUxvVSNLZq6Gv7JJUytCRaj8gXb1IjsDQmBhJinhDi//bgFirod1+ESnOLYgWS1ESBKa+VzqQQdob5dXIs/qd/eh+IN6qKAS90w5i8zXuLZSOqHWuOUwTshNCwtsRWdUltE08sPHdLP2qP/RGnPf8LeW/UdXLwh49KhdRsV7R/BjujLb1DN94BGcL3x5DTUqTUqCERGMEgq3ZHph0eFL/1yIg77KDpc= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, Mar 07, 2024 at 01:02:50AM +0000, James Houghton wrote: > Users of UFFDIO_CONTINUE may reasonably assume that a write memory > barrier is included as part of UFFDIO_CONTINUE. That is, a user may > believe that all writes it has done to a page that it is now > UFFDIO_CONTINUE'ing are guaranteed to be visible to anyone subsequently > reading the page through the newly mapped virtual memory region. > > Today, such a user happens to be correct. mmget_not_zero(), for example, > is called as part of UFFDIO_CONTINUE (and comes before any PTE updates), > and it implicitly gives us a write barrier. > > To be resilient against future changes, include an explicit smp_wmb(). > While we're at it, optimize the smp_wmb() that is already incidentally > present for the HugeTLB case. > > Merely making a syscall does not generally imply the memory ordering > constraints that we need (including on x86). > > Signed-off-by: James Houghton Reviewed-by: Peter Xu -- Peter Xu