Have no idea why stable branch missed the "fix" tag.
Jingbo Xu (2): mm: fix arithmetic for bdi min_ratio mm: fix arithmetic for max_prop_frac when setting max_ratio
mm/page-writeback.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
commit e0646b7590084a5bf3b056d3ad871d9379d2c25a upstream.
Since now bdi->min_ratio is part per million, fix the wrong arithmetic. Otherwise it will fail with -EINVAL when setting a reasonable min_ratio, as it tries to set min_ratio to (min_ratio * BDI_RATIO_SCALE) in percentage unit, which exceeds 100% anyway.
# cat /sys/class/bdi/253:0/min_ratio 0 # cat /sys/class/bdi/253:0/max_ratio 100 # echo 1 > /sys/class/bdi/253:0/min_ratio -bash: echo: write error: Invalid argument
Link: https://lkml.kernel.org/r/20231219142508.86265-2-jefflexu@linux.alibaba.com Fixes: 8021fb3232f2 ("mm: split off __bdi_set_min_ratio() function") Signed-off-by: Jingbo Xu jefflexu@linux.alibaba.com Reported-by: Joseph Qi joseph.qi@linux.alibaba.com Cc: Matthew Wilcox (Oracle) willy@infradead.org Cc: Stefan Roesch shr@devkernel.io Signed-off-by: Andrew Morton akpm@linux-foundation.org --- mm/page-writeback.c | 1 - 1 file changed, 1 deletion(-)
diff --git a/mm/page-writeback.c b/mm/page-writeback.c index 9ceb841af819..3929bb0a7501 100644 --- a/mm/page-writeback.c +++ b/mm/page-writeback.c @@ -714,7 +714,6 @@ static int __bdi_set_min_ratio(struct backing_dev_info *bdi, unsigned int min_ra
if (min_ratio > 100 * BDI_RATIO_SCALE) return -EINVAL; - min_ratio *= BDI_RATIO_SCALE;
spin_lock_bh(&bdi_lock); if (min_ratio > bdi->max_ratio) {
commit fa151a39a6879144b587f35c0dfcc15e1be9450f upstream.
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: efc3e6ad53ea ("mm: split off __bdi_set_max_ratio() function") Signed-off-by: Jingbo 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: Andrew Morton akpm@linux-foundation.org --- mm/page-writeback.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/mm/page-writeback.c b/mm/page-writeback.c index 3929bb0a7501..e7a7233f6d5d 100644 --- a/mm/page-writeback.c +++ b/mm/page-writeback.c @@ -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);
linux-stable-mirror@lists.linaro.org
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Jingbo Xu