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b=cYEmPHI4kYr6oATSI+VqxPwKjliyvrgzgV1eiOpK0h3032kT0yDSJOHCchr263Y2Z eulIy68ckZ1fI4XjPaFBXMym5A77qmLinC91yRqQ20zTlSYrtV5r5NvRJxrK/XzGyl US6JelDMIjrRVMpLQTz9K+Xh9o6dxiMj1nr8hqC8= Date: Tue, 15 Apr 2025 18:58:51 -0700 From: Andrew Morton To: alexjlzheng@gmail.com Cc: willy@infradead.org, andrea@betterlinux.com, fengguang.wu@intel.com, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, mengensun@tencent.com, Jinliang Zheng , stable@vger.kernel.org Subject: Re: [PATCH v2] mm: fix ratelimit_pages update error in dirty_ratio_handler() Message-Id: <20250415185851.e8d632f60ec5049f734ac2a8@linux-foundation.org> In-Reply-To: <20250415090232.7544-1-alexjlzheng@tencent.com> References: <20250415090232.7544-1-alexjlzheng@tencent.com> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 0ED6F140008 X-Stat-Signature: 69tq4tykwn85siy5b9cqjo7dz7e7b3nx X-Rspam-User: X-HE-Tag: 1744768733-537972 X-HE-Meta: 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 K56bUTc1 5dTR3ESueCGQaYVgMDIQpkNK0gvkZtbpGSjGOgebso2GNSvpZ4z1c+cReCiI6kQk4WG4cl1GLBpIPjZGvJodUp2lf/yPTkmBbWaDl/ThP0f0JxjWEYDneSVGymo9Xf3oKqgrCguCAJ9GOp0ZlwAN+6VLW+ymAva28N4M6bPqinGB6Kxe3ucnwOCeag7N2pbvpmu3PyIAZ/LkZquBsa7hsMtfpOzJkJWyRKv6B6MpV/tEfq4DhDlVv7oaK9vOGm49oQa4qqm/yfNKPzVTC7C0NS5+yBxk62UADF0JoiPPAJZn0ufYtriasmD7XitnLgZ1tzFiYZR76yeRQPRZTZZGHQZw6UyOd+U716Q8uWpXVJm+1TecMomUxCKXdTw== 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: On Tue, 15 Apr 2025 17:02:32 +0800 alexjlzheng@gmail.com wrote: > From: Jinliang Zheng > > In the dirty_ratio_handler() function, vm_dirty_bytes must be set to > zero before calling writeback_set_ratelimit(), as global_dirty_limits() > always prioritizes the value of vm_dirty_bytes. Can you please tell us precisely where global_dirty_limits() prioritizes vm_dirty_bytes? I spent a while chasing code and didn't see how global_dirty_limits() gets to node_dirty_ok()(?). > That causes ratelimit_pages to still use the value calculated based on > vm_dirty_bytes, which is wrong now. > > Fixes: 9d823e8f6b1b ("writeback: per task dirty rate limit") > Signed-off-by: Jinliang Zheng > Reviewed-by: MengEn Sun > Cc: stable@vger.kernel.org Please, as always, provide a description of the userspace-visible effects of this bug?