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Mon, 06 Apr 2026 02:41:15 -0700 (PDT) From: Liew Rui Yan To: sj@kernel.org Cc: aethernet65535@gmail.com, damon@lists.linux.dev, linux-mm@kvack.org Subject: Re: [PATCH v3 1/2] mm/damon/lru_sort: validate min_region_size to be power of 2 Date: Mon, 6 Apr 2026 17:41:16 +0800 Message-ID: <20260406094116.13164-1-aethernet65535@gmail.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260404203044.86655-1-sj@kernel.org> References: <20260404203044.86655-1-sj@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 135C040009 X-Stat-Signature: eegu3ozbhogxo3nzgzsafpeo78pshmmz X-HE-Tag: 1775468476-525253 X-HE-Meta: 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 qcojq7NK mbSTjK8t2Wpzv15hUq1HybOwyMSQFz9GXi1OdzKqAuEefdOfnxTlUXvmWJrPhQ3Ze1MLyugJXBLtwaCUrFyfvn+wxpPiHEmPmD+v6CHW2kZ+/lJEnpcCLKlcxG3ouHkNPGfxoEy1NTbuzUPNFPAz2Rz8pFeP4dyc8JSRJ4IpCW+lBNVFE5U+LNGs6jFpZ4b6puzqGCMUOQ/tRonTtrsxd9APvmILWdeu2Sv6MWxynsTlDHfx5Nh4gu8Oaq/r+DaO7t0TqS5J04HEFSfaLoOZFb4kjanjR1na6tS2ZFh8dXOWRmPLOffqHNcodu+pDcTQrkFYFhhjT3Bd8cuPsvliBkm8ka3G46UqG7MXGmiyJ5SVUKTYi/FV35V6vjHKwsW9S0J6ikDgzJdzwPSp5Pn8o4DMeEJo6721PpiL62hJZ0slExFsaVLNJGjVuq4SI5hMgNMHSIkQErxCbb8ibuGQlEjnPd+3ow36aq2ebCueyH4jwg5w= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Sat, 4 Apr 2026 13:30:43 -0700 SeongJae Park wrote: > On Sat, 4 Apr 2026 17:11:22 +0800 Liew Rui Yan wrote: > > > [...] > > I think this deserves Cc stable@ because: > > - The issue can be triggered by accidental user misconfiguration > > - It causes kdamond termination and hard to recover/restart. Once > > triggered, kdamond remains in an unusable state, and I have not found > > a way to recover/restart it through the sysfs interface without a > > system reboot. > > - The fix is small and low-risk > > - It improves user experience on stable kernels > > Thank you for elaborating this. I now think this deserves Cc-ing stable@. Thank you for agreeing to Cc stable@. > Let's make sure the user impact is clearly documented on the commit message. > Also, the code change itself and the current commit message is not clearly > explaining how the real problem (DAMON cannot be restarted) can happen. Please > add the description in the next revision. I will add an explanation of why DAMON cannot be restarted in the next revision. > [...] > > > > > > For stable@ Cc-ing patches, more clearly describing the user impact would be > > > nice, and helpful for judging if it deserves that. Could you please elaborate? > > > > I will add a "User Impact" section in v4's commit message: > > Yes, please add this kind of message that make clear what is the user impact. > > > > > User Impact > > =========== > > Currently, if a user commit an invalid 'addr_unit', kdamond may > > terminate abruptly. Once terminated, it cannot be easily restarted > > via sysfs, pontentially requiring a system reboot to restore DAMON > > functionality. This patch prevent such termination by validating > > parameters (addr_unit and min_region_sz) early. > > You mentioned it cannot be restarted above. The above message sounds like > there is a way to restart it via sysfs, though it is not easy. Please make it > clear and consistent. As I also requested above, please add the internal > mechanism of how that makes restart unable. This itself doesn't explain it. Thank you for your correction. I will make the description clear and consistent, and also explain the internal mechanism (the 'maybe_corrupted' flag and why writing to 'enabled' cannot recover it). Note: Please excuse my slower responses in the coming weeks, as I have upcoming exams. I will be most active and able to follow up during weekend (Friday/Saturday). Best regards, Rui Yan