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b=iPUHva13aLssUNKZdyL3hik6iWY1cm/v5s7YTF0Ichg3gjqm6xmraqBL73k8q3jHA wjt4ztB3Czdbf78qu9WzBHKlEI/OlO7aQBjzr4qgB2Pnw5l3XbQS9jEmQcK995Gbpt 1SC5r0zbWpAU7o4d2P8wuEUcyju9bdu5f8aodzzuSNkCZ984iUsQeyFiLg3WRKUKoN jFVMj+Io6AUEBaNwZhILTR+OSAfcg46osW+4SCJg07ye6hcPzWGFO98kBVKnJkY8kh ylwveh+bG+FfZT3D4UFdMYNdYsLVuoM8EHMPnB+vJ2lt9Q1bEQV6y4qOeO3mtUJi9m 9e+qBdnRiyzdA== From: SeongJae Park To: Josh Law Cc: SeongJae Park , akpm@linux-foundation.org, damon@lists.linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH 2/4] mm/damon/sysfs: check contexts->nr before clear_schemes_tried_regions Date: Fri, 20 Mar 2026 08:51:14 -0700 Message-ID: <20260320155115.101025-1-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Stat-Signature: 5k89c4stabi89xxqiebs7spafpd8ztor X-Rspamd-Server: rspam09 X-Rspam-User: X-Rspamd-Queue-Id: 202E91A0008 X-HE-Tag: 1774021882-603476 X-HE-Meta: U2FsdGVkX196G6u5HqzLcbOYAwxpvUV3nMF6CX9COLFjXHdN302fS7+7GjpPaUY+aPoUqmenoXaTlf+NCJIys36kIkn/dmf53zjDJDD2SUYaQcOPlXxwaN+E+z6mcpd0NEOtgQeVqw+5iU+YVQhEOPy1e+OzAtyKbNPN/isfWKqpWbcK0INylEVx4RTobWWnr2G0j5BEEQaSI8m/ojV99To9L1VcSWZ4VJX2C7N6MMqJBRsA5dmn8XzSyyISwiyjGQCc7AHm2HMLIQ38TOnAcF1pKbv5BlUDT+M++byzA4qYS9XlrVDvf8PpjrhfvtKQqP2NEQTObRmihiE/EVNZlGSaH/+cSk/lrxCuFQfRPeFNHuc/0tB2yl3al7ybZIe88BOJ/R8eWKS4DC+z31G3sdVt0QZ4Z0SvKMseGRypB4xDItwfjZ0wqNgsZ2kbg8GRZwiGP/LfGCh22EOCMMJYUKo3uEkGKLZPI4r/Lo8tj9Td48lMC98HM1IToaWj5PvrU8h7L+lHbezsYIPjleuOFCS1B3PA99NX9++2cYbGf8ZB49cgv0ycQJeqm0skRgjDs9ixqTvwnD0ehU8I2TWI4iaEkYQkS4iyrY6bAl0wLfjjSEDM4TZ1EjF/oacL4p6SsJGDlLoRA47oqAUKK00+yGhiW4QaXVz9dfXEnYIn9CtvtYiWW8pHmc8YUZi6nZRw6V7FiDtDKBAg5lqtXMPNEs6w2018fIzGujrZd0om7aCg7WNubhtfDsHEL/cEUELRMGEyvM8vk3jfQzohH1UdsgWM99JoiHAOsV4UcOpwoo7PFG41Y/gjmWqfEURnlLXdY78t5RlY/jpWj7D6cy+l4qtZs48EHESR2fx2qQmEbVZSKY2sr48zRMr8oSQ7XviSYtz6rFJNrNxwfvXXkgiU9oPa4ZpxM5ko3rwtczZzCnKWVJvQDRyMXeuK6+aijs/8r2aECY4ojKRopqFWsLP WRcAf0GE kPsS3aaF+reHYFhpdwmCJuQ56m+s73lS3uDf5OKMD15/uKcvMBE3gpsaroIDjCAatH/sZartGcI4efw3PrR80AzH3YSjQxhc/MYyPs0bX9PqEKzRRNBNV/iHk4EgfiYlBDeqKP1p2l7sSbkqD/bW2EoL/x0e3SGYyadQGPkNyUs64v+ZhiaygZXvbQvoPHHIxA541jO8y27k+z5ICeyBB9JaB5u6WxoEFF7KO7HiBpLJS7K3wr58y4MP9H95CstpNXbWoJMk6UO5RCKYcMvhvks3g17zWl71sVyuAzR3zVf9IQJdBJzinZRfzjLXUpm90oGO2Od8AKl+AKfg= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, 20 Mar 2026 15:14:54 +0000 Josh Law wrote: > > > On 20 March 2026 14:47:40 GMT, SeongJae Park wrote: > >On Fri, 20 Mar 2026 07:06:48 +0000 Josh Law wrote: > > > >> > >> > >> On 20 March 2026 02:13:17 GMT, SeongJae Park wrote: > >> >On Thu, 19 Mar 2026 15:57:40 +0000 Josh Law wrote: [...] > >> >Not necessarily blocker of this patch, but seems all the issues are in a same > >> >category. The third patch of this series is also fixing one of the category > >> >bugs. How about fixing all at once by checking kdamond->contexts->nr at the > >> >beginning of damon_sysfs_handle_cmd(), like below? > >> > > >> >--- a/mm/damon/sysfs.c > >> >+++ b/mm/damon/sysfs.c > >> >@@ -2404,6 +2404,9 @@ static int damon_sysfs_update_schemes_tried_regions( > >> > static int damon_sysfs_handle_cmd(enum damon_sysfs_cmd cmd, > >> > struct damon_sysfs_kdamond *kdamond) > >> > { > >> >+ if (cmd != DAMON_SYSFS_CMD_OFF && kdamond->contexts->nr != 1) > >> >+ return -EINVAL; > >> >+ > >> > switch (cmd) { > >> > case DAMON_SYSFS_CMD_ON: > >> > return damon_sysfs_turn_damon_on(kdamond); > >> > > >> >If we pick this, Fixes: would be deserve to the oldest buggy commit that > >> >introduced the first bug of this category. It is indeed quite old. > >> > > >> >Fixes: 0ac32b8affb5 ("mm/damon/sysfs: support DAMOS stats") > >> >Cc: # 5.18.x > >> > > >> > > >> >Thanks, > >> >SJ > >> > >> > >> > >> Hello, did you give Reviewed by you? Or not.. > > > >Are you meaning Reviewed-by: tag? If so, no, not yet. I want to get your > >answer to above question first. Could you please answer? > > > > > >Thanks, > >SJ > > > >[...] > > > Well, two is in the same catagory. But seperate fixes may be best. Because patch 3 dont call that function, so it may be screwy, i mean, if you want me to. Ill guard it. But its a bit on the hacky side I agree there could be more cleaner way. But these fixes need to go to stable, so I'd prefer a change that also easier to backport. So, yes, I want to. Thank you for kindly accepting my suggestion. Could you please re-post this series for the first and the fourth patches as they are, after adding my Reviewed-by:, Fixes: and Cc: stable tags, and a patch checking kdamond->contexts->nr at the beginning of damon_sysfs_handle_cmd() as I suggested? Thanks, SJ [...]