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[100.36.248.188]) by smtp.gmail.com with ESMTPSA id af79cd13be357-914f86ff80esm232992385a.13.2026.05.26.08.22.26 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 26 May 2026 08:22:27 -0700 (PDT) Date: Tue, 26 May 2026 11:22:25 -0400 From: Gregory Price To: Oleg Nesterov Cc: Alistair Popple , Andrew Morton , Byungchul Park , David Hildenbrand , Joshua Hahn , Matthew Brost , Rakie Kim , Ying Huang , Zi Yan , Jann Horn , Kees Cook , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/4] mm/mempolicy: kernel_migrate_pages: simplify the usage of put_task_struct() Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 7C9944000C X-Stat-Signature: t5q67jkj4tsndyj4xdznpoqsrsiq4cs7 X-Rspam-User: X-HE-Tag: 1779808948-74847 X-HE-Meta: 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 6OyU8Cjt eCsfgE4b8KPnFfeaDTKCiFjl9uUZNEzePSYdtVU3M2bpU0caiEOMxdrOt0dZHODKzACA79tkEzC5s4u2P8a8mtspLar+BiW8FUFkK/12oi7heqn/I5AMyxfEuBwhaCV/3mdxtbndtskjesXr2w5lvoaJTppKoXBD3h7MiOvZ4AqzgNDGnakvUEmOgXX2qPDDgSDwJRgAMTE0QUzdYe0IRZNut8gy14ZBKhew9nlNcFMVVaQ0rc1NsKYoWgmCmJF4vv4OCWN6AlrcsGpdv6x7L0Rc1O3Kfr24bTlV/Ifh4jm92v+Zq+/k09z3Vxa+qPBedPunVOh6BlicH4FLPDyveOdAKK2vJj0rqzAXEgF9rBzytT+t4Oj2JsmDp4jHSmxFExq4poLS77FquxOhYRG27LrkiZcEVQdMAR25ANYurSB4auBFuztFkDltcLpLfQtQzK3xQ Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, May 25, 2026 at 10:27:06AM +0200, Oleg Nesterov wrote: > On 05/24, Gregory Price wrote: > > > > On Sun, May 24, 2026 at 06:57:59PM +0200, Oleg Nesterov wrote: > > > > > > mm = get_task_mm(task); > > > - put_task_struct(task); > > > - > > > > Hm, I was a little trigger-happy on that review, I just realized that > > this increases the scope in which there is a task reference held (i.e. > > we're now holding a reference across do_migrate_pages()) > > > > I don't *think* that's an issue, but it might we worth looking at the > > changelog to see if this was done intentionally. > > I did this to simplify the code and the next changes. We pin this task's > memory across do_migrate_pages(), so I think that delaying put_task_struct() > doesn't add too much. > > But of course, this is not necessary, I can rework if you don't like it. > Not necessary, just a curiosity whether holding the reference across the larger scope has any functional difference. Like I said, I don't think that's an issue, but might be worth just checking the history on the function to see if it was done that way on purpose. > Thanks for review! > > Oleg. >