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b=Q4siIfZi15u7OMB0K85RsJ4IaTyccT4bNEwUt1oswHTJurxvR+tZApmiPxM/qlj1W /gVjwNZfgZHoWlQ20sUq+t4Qu4y6/EyL9yMtFy6gvrNLabvAuK6yGBzHXfmup4XCHN t6jT7CNk1R3j06zwZ+LpFKhIhy9OCd5uf2a28pLA= Date: Wed, 8 Apr 2026 14:02:51 -0700 From: Andrew Morton To: anthony.yznaga@oracle.com Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, david@kernel.org, ljs@kernel.org, Liam.Howlett@oracle.com, vbabka@kernel.org, rppt@kernel.org, surenb@google.com, mhocko@suse.com, jannh@google.com, pfalcato@suse.de, Jason@zx2c4.com, shuah@kernel.org Subject: Re: [PATCH v2 2/2] selftests/mm: verify droppable mappings cannot be locked Message-Id: <20260408140251.6158aa7a56f71128471f327e@linux-foundation.org> In-Reply-To: <83b56ffb-6e2e-4c9b-b0cf-9f04b61ebe7f@oracle.com> References: <20260402235933.10588-1-anthony.yznaga@oracle.com> <20260402235933.10588-3-anthony.yznaga@oracle.com> <20260403123120.82cb5becb19e1b572d474394@linux-foundation.org> <83b56ffb-6e2e-4c9b-b0cf-9f04b61ebe7f@oracle.com> X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 817ED40006 X-Stat-Signature: yekrc1h6fir6rdwefst97dy541nzwas6 X-Rspam-User: X-HE-Tag: 1775682173-434902 X-HE-Meta: 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 fSoQ4dpP ozU39O8WiKg3jGs5qnOLRPZrHzvWpr+o6ZZBZA55d8R7xhw0ZeZUj6CV3MaO04q+MX0IsB6YUbzW2sJ6sLecOU5B2uEbqPJvdHNmJ7v1AWUdWs2u1RU3tVQFTG/c5DuV5TKMAEdn50JjgtZWZje+t/syddafVCPEHvT4+vRwSXyfOOyHTYwBCWIc402IKQd42Lm2lA3STYmyA/TSxrZr8idTBopL8xRM4l61jcGovaDG1ZkTk06oK8WQNwcVlBSzbqJn4BLL73l+N06qyh5FVLCBXhTD6aKBn4RHx6xiP92FsdcZBtsunEjLf6cuuTddjDNbgPnfH2CDqNpc= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, 8 Apr 2026 13:35:42 -0700 anthony.yznaga@oracle.com wrote: > > On 4/3/26 12:31 PM, Andrew Morton wrote: > > On Thu, 2 Apr 2026 16:59:33 -0700 Anthony Yznaga wrote: > > > >> For configs that support MAP_DROPPABLE verify that a mapping created > >> with MAP_DROPPABLE cannot be locked via mlock(), and that it will not > >> be locked if it's created after mlockall(MCL_FUTURE). > > There are a few queries from the AI reviewbot; > > https://sashiko.dev/#/patchset/20260402235933.10588-1-anthony.yznaga@oracle.com > > Interesting. Of the two issues, one is certainly legit. I need to add an > munlockall() on early return from test_mlockall_future_droppable(). Cool. > For the other, the question posed was whether the tests should handle > possibly being run on an older kernel that doesn't implement > MAP_DROPPABLE. It seems to me to that a selftest should not be expected > to work (or even necessarily compile) on kernels older than when the > selftest was introduced, but I don't want to assume. I don't know that there's any policy on that. My attitude is that selftests are not intended to be forward- or backward-compatible. That's why we ship them with the kernel source! If we get a selftests fixup then I do like to backport that into earlier kernels if appropriate, to keep those in good shape. And that has the effect of reducing people's motivation to run a later kernel's selftests on their current kernel.