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b=mTBZi2+AvRTWYk+wBgldQYvdYBAVIdINkvVX3c1ew+3uRhPqp33ntUYux6d0uog68 jZ/QcdECygiJLPjqjgORCJXtnZF9o6iwmUkKLEp5ypNhLpIUBOC2iHVAgkSQdnmwQf f9UHCueduHcGbaeiTYMwp2QviwVwpj1CvhkvmY4tz5YmtgkvJ3cnwRrzg7PyiG9ldK fyTv5RbMUHfi2RrEXX4bfGw8LoY8sROoaPsM3my3URDtBjeUuHrccAkJPn4g4R4kdW Ict88pNFadtt/GFX3o4Gq1uphx5TEqePtZXvk/0N46pVmszreGRlOTGQSU0h1+Cdhh ndZE7qmLcLlHA== From: SeongJae Park To: SeongJae Park Cc: Andrew Morton , "# 5 . 18 . x" , Jiapeng Chong , damon@lists.linux.dev, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH 0/4] mm/damon/sysfs: free setup failures generated zombie sub-sub dirs Date: Fri, 2 Jan 2026 16:21:37 -0800 Message-ID: <20260103002139.66559-1-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20251225023043.18579-1-sj@kernel.org> References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: E69781C000A X-Stat-Signature: gwn5kxs9x89h8kgwnwspgyd3sj6thcge X-Rspam-User: X-HE-Tag: 1767399704-656092 X-HE-Meta: U2FsdGVkX19oPhPHPZx3AWIyHh9f0DVvTFjAGpX3e9vvXXRf4tIEk36hLuiaTdQ6A95igWMEnuJ5wxdvhLl4KroIc0sD0aaVfe1HVv5hYh0kjvi8WGPq18oAUztPOUOPDPvfIX0RsnQ4hbn6JcZ8F1CUbQSDDquu/qAbG0ytmVjqrBlNt0WfjT4JK/HRZYJuVXe7YN1qg4MJEpo/ub4Wz9s/JkoQ/Jv99QjuxiTOKWjhOm2KGn0KBEeohxZzCQ197bPvOx7M+j/f5SRNNiY2KQQPZzaQnOzR6W469v1FgAb7UTXuaOQH4bRHbhdMKIZE1yWtKMUZ8s+IZTyU+pHbVP35ZgK02ECFiAvQvUb4NwejD/bTYSSp37YhajdVDsY06DZTod9pJz9yDcRNjQSp00MsYKjPoRVL06gf96HN0NehwljvUHwscDdRto5CQuLFXbQWZuQNzJHbRjRWvDhPxHuyJrVxjfkC9IS5iQabZlf23pPys9lXaSF/tMQuw/cSjPRWI9jy9lJqahIeqTeEo9wP7uTROh8wcpTd/A8lJlV4NF9G7JLyCj8k1ccEoVnwLy/PVL3QZQIepRNMpwpNhF9pUQvQr/JIG49r5svm3pTrNmYdGNGDRbS6TVTXV5lcJyHx7ert36yoK+l/ZdOWiEUFZrC5llV5y1O/6//3/LCBZ5kvOX40cso+ZE/9DC5hXIDQQnC4qHdxPXEGLlqn/R8y/iMVX+hcAGnMNZjin28yKJgDvcyGDkCt3bb1YG8ULd4Ob1i/y2QEKNh3QpN1tkvmVTDn0dl2r14FJkF8/wz4onUTDSR7TMi5ks5/HvWfr2omfFb6hWVrGztwvhgroYwaxmP4ZQiK4RnewmoeSl7Dz6qSyRXNZUo2UAvQosyoAnXhkYTRyj4eRbBhf8scmtRKBZ9Y8QLxKIcnj20MVzGqHV0RlHiVamutN1bX5lNXvpRxCUVk5gRsPHUQPli 8BOPQKY5 60N1Tirz+uafMpNMXCGsktLYUr3NTvoULbYYbo4a1EDU9rq9OIWQIGoSLP5i7Z5cJhVKWeR9cAkGMy1xS2fEwM9noDOsHkWAXgd0tqAXyj0RiKrdCoPcMLAHt7nBU8PF9D2XWlmB2VxQl6VUaDiuQw34U7tzxbuBwjKv2xbZNdu33gn5Glk0BbAHbRkdlTnOSoiPXFj6mmDnDOoKtGJ7UU33obL0iozpjBAARy3Wum+K22ow= 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: Hello Andrew, happy new year! On Wed, 24 Dec 2025 18:30:33 -0800 SeongJae Park wrote: > Some DAMON sysfs directory setup functions generates its sub and sub-sub > directories. For example, 'monitoring_attrs/' directory setup creates > 'intervals/' and 'intervals/intervals_goal/' directories under > 'monitoring_attrs/' directory. When such sub-sub directories are > successfully made but followup setup is failed, the setup function > should recursively clean up the subdirectories. > > However, such setup functions are only dereferencing sub directory > reference counters. As a result, under certain setup failures, the > sub-sub directories keep having non-zero reference counters. It means > the directories cannot be removed like zombies, and the memory for the > directories cannot be freed. > > The user impact of this issue is limited due to the following reasons. > > When the issue happens, the zombie directories are still taking the > path. Hence attempts to generate the directories again will fail, > without additional memory leak. This means the upper bound memory leak > is limited. Nonetheless this also implies controlling DAMON with a > feature that requires the setup-failed sysfs files will be impossible > until the system reboots. > > Also, the setup operations are quite simple. The certain failures would > hence only rarely happen, and are difficult to artificially trigger. The user impact of the bugs is limited as explained above, but the bugs exist in the code for real world usages. I therefore expected this series would be added to mm-hotfixes-unstable. Do you have any concern at treating this series as hotfixes? If not, could you please move this series into mm-hotfixes-unstable? Thanks, SJ [...]