As we test disk offline/online with running fsstress, we find fsstress
process is keeping running state.
kworker/u32:3-262 [004] ...1 140.787471: ext4_mb_discard_preallocations: dev 8,32 needed 114
....
kworker/u32:3-262 [004] ...1 140.787471: ext4_mb_discard_preallocations: dev 8,32 needed 114
Test step:
1. sysctl kernel.panic_on_oops=1
2. mkfs.ext4 -O^has_journal /dev/sdc
3. mount /dev/sdc -o errors=continue test
4. ./fsstress -d ./test/ -l 1000 -n 1000000 -p 1 &
5. run test script:
while true; do
echo offline > /sys/block/sda/device/state
sleep 0.05
echo running > /sys/block/sda/device/state
done
ext4_mb_new_blocks
repeat:
ext4_mb_discard_preallocations_should_retry(sb, ac, &seq)
freed = ext4_mb_discard_preallocations
ext4_mb_discard_group_preallocations
this_cpu_inc(discard_pa_seq);
---> freed == 0
seq_retry = ext4_get_discard_pa_seq_sum
for_each_possible_cpu(__cpu)
__seq += per_cpu(discard_pa_seq, __cpu);
if (seq_retry != *seq) {
*seq = seq_retry;
ret = true;
}
As we see seq_retry is sum of discard_pa_seq every cpu, if
ext4_mb_discard_group_preallocations return zero discard_pa_seq in this
cpu maybe increase one, so condition "seq_retry != *seq" have always
been met.
To Fix this problem, ext4_get_discard_pa_seq_sum function couldn't add
own's cpu "discard_pa_seq" value.
Fixes: 07b5b8e1ac40 ("ext4: mballoc: introduce pcpu seqcnt for freeing PA to improve ENOSPC handling")
Signed-off-by: Ye Bin <yebin10@xxxxxxxxxx>
---
fs/ext4/mballoc.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index 132c118d12e1..168ea3e65da2 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -373,10 +373,12 @@ static DEFINE_PER_CPU(u64, discard_pa_seq);
static inline u64 ext4_get_discard_pa_seq_sum(void)
{
int __cpu;
+ int this_cpu = smp_processor_id();;
u64 __seq = 0;
for_each_possible_cpu(__cpu)
- __seq += per_cpu(discard_pa_seq, __cpu);
+ if (this_cpu != __cpu)
+ __seq += per_cpu(discard_pa_seq, __cpu);
return __seq;
}
--
2.25.4
