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b=FqzlQIMIU5uJ6vkK3AJRW3tNLUxxwp34FMFZaZUVyD19bE09e4OAPqxqwgGhoYRuQ HZYPmQEAWVfo63FgqJ+Bro1Jdj1onIt5Nvalp40bMq84vIWL0FOdvvlGpBNMvvz7Ov GLVQNdi7NDY+deDfKiq6siu1smYYCALPUZACuQo07DxOX5zZyr1xvRnnkgnIQxNoz5 kHyrlIwR3wC96LVrFxTZ8usSCpTQnPqiVh7jN2fYeTtB+KuMGKZfObkzwlUT6Z9ifD lsWD+kaybyFFzXdfdWeVylx0B7i78JDm6GaPDywMqs1Db4Z6CWKnAu0Bby4gs0HS76 xOpw0o9Di+SaQ== From: SeongJae Park To: wangchuanguo Cc: SeongJae Park , akpm@linux-foundation.org, hannes@cmpxchg.org, david@redhat.com, mhocko@kernel.org, zhengqi.arch@bytedance.com, shakeel.butt@linux.dev, lorenzo.stoakes@oracle.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, damon@lists.linux.dev, Jagdish Gediya Subject: Re: [PATCH 1/2] mm: migrate: restore the nmask after successfully allocating on the target node Date: Wed, 28 May 2025 15:09:42 -0700 Message-Id: <20250528220942.55350-1-sj@kernel.org> X-Mailer: git-send-email 2.39.5 In-Reply-To: <20250528111038.18378-2-wangchuanguo@inspur.com> References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: 094B140016 X-Stat-Signature: 88pxxk1a4umgcfrsyxegneojow6wiifd X-Rspam-User: X-Rspamd-Server: rspam07 X-HE-Tag: 1748470186-449466 X-HE-Meta: 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 6ImFvZTo 21+UvSmpB/yxmzUcubnAcYPlOAniv43hu7ZaC8JOaIxG7ui5Ka4iryab+5y7PTVwqXClzbyEAHoM8dzhJD4QLs6MEYd8fcsmGX5IRqBg2q/EW+rDsVlyhAYVlcThhW7U+Ryc3+pTJLDPqz3P+VOjxQmBupqqJH27XbsFqDmyi25crbNxGym7DocL9pjINqJAyPT56fPkThHFEo6geXH+fc+JswC/sHouvGaAQMgDreh7JaTK82k4CfDoB9YdFGbcSxXlmlOGPm/6JJxU6V8q8obfXVl24D3cTW/ym1SCN7I4mX17jVt2SsFw/l1Mal7GaHMaxfYGvxoTbxUb2HvuxVrXeJQ== 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: List-Subscribe: List-Unsubscribe: + Jagdish, since seems the behavior that this patch tries to change is apparently made by Jagdish's commit 320080272892 ("mm/demotion: demote pages according to allocation fallback order"). On Wed, 28 May 2025 19:10:37 +0800 wangchuanguo wrote: > If memory is successfully allocated on the target node and the > function directly returns without value restore for nmask, > non-first migration operations in migrate_pages() by again label > may ignore the nmask settings, Nice finding! > thereby allowing new memory > allocations for migration on any node. But, isn't the consequence of this behavior is the opposite? That is, I think this behavior restricts to use only the specified node (mtc->nid) in the case, ignoring more allowed fallback nodes (mtc->nmask)? Anyway, to me, this seems not an intended behavior but a bug. Cc-ing Jagdish, who authored the commit 320080272892 ("mm/demotion: demote pages according to allocation fallback order"), which apparently made this behavior initially, though, since I may misreading the original author's intention. > > Signed-off-by: wangchuanguo > --- > mm/vmscan.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/mm/vmscan.c b/mm/vmscan.c > index f8dfd2864bbf..e13f17244279 100644 > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -1035,11 +1035,11 @@ struct folio *alloc_migrate_folio(struct folio *src, unsigned long private) > mtc->nmask = NULL; > mtc->gfp_mask |= __GFP_THISNODE; > dst = alloc_migration_target(src, (unsigned long)mtc); > + mtc->nmask = allowed_mask; > if (dst) > return dst; Restoring ->nmask looks right behavior to me. But, if so, shouldn't we also restore ->gfp_mask? > > mtc->gfp_mask &= ~__GFP_THISNODE; > - mtc->nmask = allowed_mask; > > return alloc_migration_target(src, (unsigned long)mtc); > } > -- > 2.39.3 Thanks, SJ