Hi Sergey, > On (22/11/10 15:29), Martin Doucha wrote: > > New version of LTP test zram01 found a sysfile issue with zram devices > > mounted using VFAT filesystem. When when all available space is filled, e.g. > > by `dd if=/dev/zero of=/mnt/zram0/file`, the corresponding sysfile > > /sys/block/zram0/mm_stat will report that the compressed data size on the > > device is 0 and total memory usage is also 0. LTP test zram01 uses these > > values to calculate compression ratio, which results in division by zero. > > The issue is specific to PPC64LE architecture and the VFAT filesystem. No > > other tested filesystem has this issue and I could not reproduce it on other > > archs (s390 not tested). The issue appears randomly about every 3 test runs > > on SLE-15SP2 and 15SP3 (kernel 5.3). It appears less frequently on SLE-12SP5 > > (kernel 4.12). Other SLE version were not tested with the new test version > > yet. The previous version of the test did not check the VFAT filesystem on > > zram devices. > Whoooaa... > > I've tried to debug the issue and collected some interesting data (all > > values come from zram device with 25M size limit and zstd compression > > algorithm): > > - mm_stat values are correct after mkfs.vfat: > > 65536 220 65536 26214400 65536 0 0 0 > > - mm_stat values stay correct after mount: > > 65536 220 65536 26214400 65536 0 0 0 > > - the bug is triggered by filling the filesystem to capacity (using dd): > > 4194304 0 0 26214400 327680 64 0 0 > Can you try using /dev/urandom for dd, not /dev/zero? > Do you still see zeroes in sysfs output or some random values? I'm not sure if Martin had time to rerun the test. I was not able to reproduce the problem any more on machine where the test was failing. But I'll have look into this during this week. Kind regards, Petr
