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[172.10.233.147]) by smtp.gmail.com with ESMTPSA id z3-20020ac87f83000000b002deae661c08sm4106469qtj.33.2022.03.04.14.48.09 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 04 Mar 2022 14:48:10 -0800 (PST) Date: Fri, 4 Mar 2022 14:48:08 -0800 (PST) From: Hugh Dickins X-X-Sender: hugh@ripple.anvils To: Liam Howlett cc: Hugh Dickins , Andrew Morton , Oleg Nesterov , "linux-kernel@vger.kernel.org" , "linux-mm@kvack.org" Subject: Re: [PATCH mmotm] mempolicy: mbind_range() set_policy() after vma_merge() In-Reply-To: <20220304190531.6giqbnnaka4xhovx@revolver> Message-ID: <6038ebc2-bc88-497d-a3f3-5936726fb023@google.com> References: <319e4db9-64ae-4bca-92f0-ade85d342ff@google.com> <20220304184927.vkq6ewn6uqtcesma@revolver> <20220304190531.6giqbnnaka4xhovx@revolver> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII X-Rspamd-Queue-Id: 6BD5D140010 X-Stat-Signature: 5h3b5t7kotz4zs1ctzwg4p189gis95gu X-Rspam-User: Authentication-Results: imf23.hostedemail.com; dkim=pass header.d=google.com header.s=20210112 header.b=BQJXzgwm; dmarc=pass (policy=reject) header.from=google.com; spf=pass (imf23.hostedemail.com: domain of hughd@google.com designates 209.85.160.169 as permitted sender) smtp.mailfrom=hughd@google.com X-Rspamd-Server: rspam03 X-HE-Tag: 1646434091-564171 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 Fri, 4 Mar 2022, Liam Howlett wrote: > * Liam R. Howlett [220304 13:49]: > > * Hugh Dickins [220303 23:36]: > > I just thought of something after my initial email > > How does the ->set_policy() requirement on tmpfs play out for the > mpol_equal() check earlier in that for loop? It took me a while to page all this back in (and remind myself of what is case 8) to answer that question! The answer is that the mpol_equal() check at the top of the loop is on an existing, unmodified vma; so it's right to assume that any necessary set_policy() has already been done. Whereas the mpol_equal() check being removed in this patch, is being done on a vma which may have just been extended to cover a greater range: so although the relevant set_policy() may have already been done on a part of its range, there is now another part which needs the policy applied. > > Reviewed-by: Liam R. Howlett Thank you, your review is very welcome (but mainly I Cc'ed to alert you to how I'm probably stepping on your toes a little here - sorry). Hugh