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Shutemov" To: Hugh Dickins Cc: Andrew Morton , "Kirill A. Shutemov" , Andrea Arcangeli , Song Liu , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH] khugepaged: collapse_pte_mapped_thp() flush the right range Message-ID: <20200802210738.i4trrpq5b77yaxzw@box> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Queue-Id: E0E02180F8B86 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam02 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: On Sun, Aug 02, 2020 at 12:12:42PM -0700, Hugh Dickins wrote: > pmdp_collapse_flush() should be given the start address at which the huge > page is mapped, haddr: it was given addr, which at that point has been > used as a local variable, incremented to the end address of the extent. > > Found by source inspection while chasing a hugepage locking bug, which > I then could not explain by this. At first I thought this was very bad; > then saw that all of the page translations that were not flushed would > actually still point to the right pages afterwards, so harmless; then > realized that I know nothing of how different architectures and models > cache intermediate paging structures, so maybe it matters after all - > particularly since the page table concerned is immediately freed. > > Much easier to fix than to think about. > > Fixes: 27e1f8273113 ("khugepaged: enable collapse pmd for pte-mapped THP") > Signed-off-by: Hugh Dickins > Cc: stable@vger.kernel.org # v5.4+ Acked-by: Kirill A. Shutemov -- Kirill A. Shutemov