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Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Usama Arif , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Shuah Khan , Kevin Brodsky , linux-mm@kvack.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v5 3/3] kselftest: mm: introduce alloc_isolated_mem() Message-ID: References: <20260907-fix_split-v5-0-822b810458bc@arm.com> <20260907-fix_split-v5-3-822b810458bc@arm.com> <5c05b620-7a2f-453d-9725-fed4f536a019@kernel.org> <31418d0e-9745-4e8d-bc02-dbbd5cb9e193@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <31418d0e-9745-4e8d-bc02-dbbd5cb9e193@kernel.org> X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: CD4BF40008 X-Stat-Signature: 3ns9wcmstfxykg6gtwsa8bbgpejgzdgn X-Rspam-User: X-HE-Tag: 1789039833-490979 X-HE-Meta: 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 vHx0yPTG dLmShKlp6SZLxqP2gq2UkWrcCiNRrxFMOk3l2he7BQK4q/hQoHCDeoFc2GJZhAZj9YELnlA2Ftc/OXOHI5ALvxzmLVBFqGAXJAJa2HKgDNh7LoDDhd0IHELWjCSOhogjnRgTQvZgJSTuB6q2yHru5pr0yVEK+VFYBX+pCRt5cd3jSR8pvmH6ZGNoggcRZA8I+ceeFiolhrj+jtCui/k14jJ9OoJ5hEkE8PDwogyfSZSMsReYaYOPhlsmJukFhnwleQW6fqEEdOj1Jf9chHLIeJIiLSbMYjq+ePzpIUJwlddjYju/p7zhaqj8L6g== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: > On 9/10/26 13:22, Yeoreum Yun wrote: > > On Thu, Sep 10, 2026 at 01:14:42PM +0200, David Hildenbrand (Arm) wrote: > >> On 9/10/26 13:02, Yeoreum Yun wrote: > >>> > >>> Since there is no interface to get vm_flags not via /proc/self/smaps, > >>> It might be good to have it for preventing unwanted VMA merge. > >>> > >>> And might be useful for future to prevent unwated VMA merge. > >> > >> See my reply on why vm flags are generally not a problem. Just like other > >> properties that are not changed during VMA merging. > >> > >> Let's not perform random code changes without a clear picture. > >> > >> And just to emphasize again: VMA merging could already be a problem before > >> memalign() internal changes. > >> > >> (also observe here how we do a MADV_HUGEPAGE, so this is all rather arbitrary, > >> which is not good) > > > > As I mentioned in my previous reply, what I’m trying to prevent here is > > a failure when checking, immediately after memory allocation, > > that a specific vm_flag is not set. > > > > Yes, I agree that this could have been a problem even before > > the internal changes to memalign(). An unwanted VMA merge could already > > occur at the time of memory allocation. > > > > So what I’m trying to avoid is a test failure where, due to such an > > unexpected VMA merge during allocation, the subsequent check that > > a specific vm_flag is not present fails. > Which is only a guard-region marker problem? Yes. so if we remove ASSERT_FALSE(check_vmflag_guard(ptr)), TBH we don't need this patch unless other usage comes up to prevent unwanted VMA merge. Would it be better to drop ASSERT_FALSE(check_vmflag_guard(ptr)) in guard test? -- Sincerely, Yeoreum Yun