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b=VxfOEtrqIoqIK5xImd1RD9szFaJb+642xnsx+4gFfvd/ngO5LzRGs6cxaJhiSR/7X Wo2YCskKacWVCI5E/RJVQJmduIxdk46iUaLiDEx5o5fX7ZeD7cS+hgwnRBWZwU9xAi U6/7XI9b0mH/1TA6xUen/ZnKcDJsthpP175NtyphpPaEBudZf8o49YRdHpS1nziqEq Phr9xdWYresJUuQRSx9LjCyphG1I+2Om4MMLVv4T0ePuk0Ppc/gFdcXAXjG6iGGXRF fTHh+zs6HjGwxDNEH6RlnmTF8ohK8LwV+O3JFniT4OgmtQk0+/pnMSP8KtB1az7JXR q0Y9ArRK2EO0Q== From: SJ Park To: dayou5941@163.com Cc: SJ Park , akpm@linux-foundation.org, damon@lists.linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org, joshua.hahnjy@gmail.com, liyouhong , stable@vger.kernel.org Subject: Re: [PATCH v3] mm/damon/ops-common: putback folios on invalid migrate nid Date: Sun, 26 Jul 2026 09:50:05 -0700 Message-ID: <20260726165005.88635-1-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260726014815.1280757-1-dayou5941@163.com> References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 9C0A14000B X-Stat-Signature: i4y3tynijxw4yhs9cmcfefi9xczbsbun X-HE-Tag: 1785084614-62 X-HE-Meta: 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 NATeFOrE lBDVIuq5wOCvynahIu4BJOUV2pr7+i3KqQ5yermP8AFKbbx8JEm6iriUISmlWLphqXAdZPM+byIDqCkcoxFUvgBxGp4slPEf4IIMcAy1JvNTZ0d0L0lZcUwn58ayaTyiARA/moT07+0z2g4LHSu9+51oO9/D2DXtqcoWj8rB4d1qSwfPKkhibbKhrKQrSQEPgsmfjS/2ODBsgIYnnZHGrObHXzGr3gwKxAsINZOQHef+qNDK8bRnza3RxGvI7G78cInCl9H5lIaAY486Llmolt3ZELW2o+wXoIFUgK4Y8yu0mAGFOH9B+ehM4td5E0h3oZp600EhzqMaCUdCqPVk3cZ7XyzKtl5UA9GLD Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Sun, 26 Jul 2026 09:48:15 +0800 dayou5941@163.com wrote: > From: liyouhong > > damon_pa_migrate() and damos_va_migrate() isolate folios into a local list > and then call damon_migrate_pages(). When target_nid is invalid (including > the scheme default NUMA_NO_NODE / -1), damon_migrate_pages() returns early > without putting the folios back to the LRU. > > Callers then discard the list head while those folios remain isolated with > an extra reference taken by folio_isolate_lru(). The pages stay off the > LRU for as long as the mapping exists (anon active+inactive counts drop > while RSS does not), and the leftover references can pin the pages after > the mapping is gone. > > Put the folios back on the invalid-nid path so ignored migration requests > still return them to the LRU. Looks good to me, thank you for catching and fixing this, liyouhong! Andrew, I think this deserves the hotfix fast track. The bug can cause memory pressure, and can be reliably reproduced by the user. The user should already have a sysfs write permission, though. Let me know if you think differently. This patch is applied to damon/next [1] tree. If this patch is not added to mm.git in short term (~1 week?), I will ask mm.git maintainer (Andrew Morton) to pick this. So, no action from your side is needed for now. If it seems I also forgot doing that or you cannot wait for my action, please feel free to directly ask that to Andrew. [1] https://origin.kernel.org/doc/html/latest/mm/damon/maintainer-profile.html#scm-trees Thanks, SJ