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mm/page-writeback: avoid 32-bit overflow in dirty threshold shares - #2945
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The ratios used by __wb_calc_thresh() are scaled to parts per million, but the threshold and ratio operands are unsigned long. On 32-bit kernels, their multiplication can wrap before the result is assigned to u64. For example, with a threshold of 25600 pages and the default maximum ratio of 1000000, wb_max_thresh becomes 4125 pages instead of 25600. The shared threshold and minimum share calculations can overflow in the same way, producing incorrect per-writeback dirty limits. Use a u64 threshold for the three ratio multiplications and div_u64() to retain the existing division order and rounding. Fixes: ae82291 ("mm: use part per 1000000 for bdi ratios") Cc: stable@vger.kernel.org Signed-off-by: Hungyu Lin <dennylin0707@gmail.com> Reviewed-by: Gregory Price (Meta) <gourry@gourry.net> Reviewed-by: Jan Kara <jack@suse.cz>
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Superseded by series 1190105 (v1). Closing automatically. Automated by ml2pr |
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Series: https://patchwork.kernel.org/project/linux-fsdevel/list/?series=1190219
Submitter: Hungyu Lin
Version: 2
Patches: 1/1
Message-ID:
<20261021060654.27855-1-dennylin0707@gmail.com>Base: vfs.base.ci
Lore: https://lore.kernel.org/linux-fsdevel/20261021060654.27855-1-dennylin0707@gmail.com
Automated by ml2pr