Commit 94643128 authored by Jingbo Xu's avatar Jingbo Xu Committed by Liu Shixin
Browse files

mm: fix arithmetic for max_prop_frac when setting max_ratio 

mainline inclusion
from mainline-v6.7
commit fa151a39a6879144b587f35c0dfcc15e1be9450f
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/IBE0E0

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=fa151a39a6879144b587f35c0dfcc15e1be9450f

--------------------------------

Since now bdi->max_ratio is part per million, fix the wrong arithmetic for
max_prop_frac when setting max_ratio.  Otherwise the miscalculated
max_prop_frac will affect the incrementing of writeout completion count
when max_ratio is not 100%.

Link: https://lkml.kernel.org/r/20231219142508.86265-3-jefflexu@linux.alibaba.com


Fixes: efc3e6ad ("mm: split off __bdi_set_max_ratio() function")
Signed-off-by: default avatarJingbo Xu <jefflexu@linux.alibaba.com>
Cc: Joseph Qi <joseph.qi@linux.alibaba.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Stefan Roesch <shr@devkernel.io>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLiu Shixin <liushixin2@huawei.com>
parent 9a9f904d

mm/page-writeback.c

+2 −1
Original line number Diff line number Diff line
@@ -750,7 +750,8 @@ static int __bdi_set_max_ratio(struct backing_dev_info *bdi, unsigned int max_ra 
		ret = -EINVAL;

	} else {

		bdi->max_ratio = max_ratio;

		bdi->max_prop_frac = (FPROP_FRAC_BASE * max_ratio) / 100;

		bdi->max_prop_frac = (FPROP_FRAC_BASE * max_ratio) /

						(100 * BDI_RATIO_SCALE);

	}

	spin_unlock_bh(&bdi_lock);