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AJvYcCXvJ3bIs224BdDpqRA7LJIAEQpL3UAtW0sTxQL7ALYXuJv9bsTbYVV5jDMhCrKooq/usdNIVJI0Jo6Qg50MDQ59dX4= X-Gm-Message-State: AOJu0YzL1iSn9mRwY/e0k3xQxk7GJFYcKcuOQIgtDawxhdNFj1a8arRK 7fahxlpxe4PJiX9CoV6yjvkGW3QyBqsKvl1VM6R1Lxq6KGUktmSHDsc6EaQCKj9ULV6vk+M61Ru 2I0pih8vECr6hEnuFXeW2r07KtZtkgkmeCS3+ X-Google-Smtp-Source: AGHT+IFCqhqWyFw06uhWIdpoEoci5WQ84TqCrDo7xDu6Un3b/I5G1wLJTN4tyEMXlmp7ovol4oJY7zRNpVLDwuLsN0Q= X-Received: by 2002:a05:6402:26d4:b0:57c:b712:47b5 with SMTP id 4fb4d7f45d1cf-57d3f5fbf99mr20040a12.4.1718991017488; Fri, 21 Jun 2024 10:30:17 -0700 (PDT) MIME-Version: 1.0 References: <20240621144017.30993-1-jack@suse.cz> <20240621144246.11148-2-jack@suse.cz> <20240621101058.afff9eb37e99fd48452599b7@linux-foundation.org> In-Reply-To: <20240621101058.afff9eb37e99fd48452599b7@linux-foundation.org> From: "Zach O'Keefe" Date: Fri, 21 Jun 2024 10:29:39 -0700 Message-ID: Subject: Re: [PATCH 2/2] mm: Avoid overflows in dirty throttling logic To: Andrew Morton Cc: Jan Kara , linux-mm@kvack.org, linux-fsdevel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 2B96E2000B X-Stat-Signature: a14h4p5ytyy9u7a7k7kduzxcuyrkopbs X-HE-Tag: 1718991018-711757 X-HE-Meta: U2FsdGVkX1+JGkc7Ul8wYtHLWT6ymKAGm38RY6KPz15Zxo2WxUor1NQ3zV9H3oEBfIYWVVgTYm/drPU5lXTj31Pc6rPMZLdq34RtpU6R7cC/jRtzKDU93LZbR0+49x33vRVS29bF2Onm2Vfweat3mKj9wDyA+Qp1I6F5NLFxax+DAjDe6D3fYaswUvlI+ka/PPLM5iOadJWeE38Np92Vib5EMLIIVNdsWUmyGDgUtybeBEzByxOlncl79kNVZ/dnarv791kwjLSBHrnr1ZEdzm3UU9AtQDMnwHF9sJ8BU5/1mj+Qhs7JTwO+yrDTaCZipFxvYfV/OUwlK27nKJ+5Utx66Qtc1dopo7zxgb89s0Yo9WxvsltcmMVwRhtZ9xBSxQ0vtggHHQqYbKdcNaZHBg5HlvnUp8X0l9xhC8HaSxdYD4Tp5SA7TXicw0Ok64FBRgV9K11e1Xl/oWRfkPlobzWYfNcQak9bwff6yWYHCLWNS1WKAsFig3rd56HU238qny/Th0Qw5KmhE57lItN4mjZkDOVNL5Jj5mutYIzXTmza786fj8e7Ik3uMFWs/ialr9LkbQheXuoLY/EdtbmO/DmnNmIDJnjItrNJ/YkrYdFmssy4y/sY+CZtKwifZAKMrObOsl0SOnO4+XM+HXE7NKsWVtY2HXNJ0yJSgnhH7vMaadkdjp1lRkMYi+fEeIrBJRXx2MOZWTHRYqjjr3njgCmy8jmaOr+DpaU8VrnyRmqhdxsCaIj0MdenDwAo7Uy2Bitzg7JCAgZK3IrZv0XVOSqlVJbvR9cbS8+qIvjPfBbvQR+FUUny+1zEpxR1FHAtSYWQm1RURrvV7lu88lyQkeuL0AhPCLOVjfifBOe9VxG5gT6S1mq7r0SUbHTh848T+ownotAdHnNdwJnOclu7POqHrBSpL5u5B9dS0fLp5bon1wEGkvlS/CUoLgy1g83x1W/SC10EFO6GJbaxNf+ gKFMRAqQ I7pvlGREJy4cSYXA5wR05LhHKqjqjulSy8m9NjM/8mwf2vYuX8H25HASuLj7yX+jV45s/RrQthCgXJ8j2eXGGIhEEGZ1MDI6bvYfkZhxv28WZAlKOILAZ65HmeOFuOxrw4RHXBm/vDd/udqlDt0mLgZfudyyyuF9lMxIn5wPAPabmfM0ENbL3WX0P84qu7e6F7Pdpfegh998J/qHBsGRCoXtwdbBwDh/FgalmCIvjHgpoSMLI2f+d8NTW4w== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000093, 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 Fri, Jun 21, 2024 at 10:11=E2=80=AFAM Andrew Morton wrote: > > On Fri, 21 Jun 2024 16:42:38 +0200 Jan Kara wrote: > > > The dirty throttling logic is interspersed with assumptions that dirty > > limits in PAGE_SIZE units fit into 32-bit (so that various > > multiplications fit into 64-bits). If limits end up being larger, we > > will hit overflows, possible divisions by 0 etc. Fix these problems by > > never allowing so large dirty limits as they have dubious practical > > value anyway. For dirty_bytes / dirty_background_bytes interfaces we ca= n > > just refuse to set so large limits. For dirty_ratio / > > dirty_background_ratio it isn't so simple as the dirty limit is compute= d > > from the amount of available memory which can change due to memory > > hotplug etc. So when converting dirty limits from ratios to numbers of > > pages, we just don't allow the result to exceed UINT_MAX. > > > > Shouldn't this also be cc:stable? +1 for stable, following previous attempts to address this. Either way, it seems this closes the door on the particular overflow issue encountered previously. Thanks for the proper fix. Reviewed-By: Zach O'Keefe