Control: tags -1 + moreinfo On Sat, Aug 05, 2023 at 12:45:18PM -0700, Corey Hickey wrote: > Package: src:linux > Version: 6.3.11-1 > Severity: normal > > Dear Maintainer, > > I was testing RAID-5 write-back journal (AKA cache) for the first time. > > https://docs.kernel.org/driver-api/md/raid5-cache.html > > I experienced a NULL pointer dereference early in the process. > > -------------------- steps leading up to the crash ------------------- > > Make a RAID-1 from a pair of SSDs. > > $ sudo mdadm --create /dev/md101 -l 1 -n 2 > /dev/disk/by-id/ata-Samsung_SSD_850_PRO_256GB_S251NX0H60631* > > Make a RAID-5 containing the journal and three block device (one of > which is, in turn a RAID). Size is restricted to 10 GB for testing > purposes. > > $ sudo mdadm --create /dev/md5 -n 3 -l 5 -z 10G --write-journal /dev/md101 -c > 128K /dev/disk/by-id/ata-TOSHIBA_HDWG21C_* /dev/md3 > > I waited for the RAID to re-sync (this is necessary in order to enable > write-back jornal mode, though not documented). > > Enable write-back mode: > > $ echo write-back | sudo tee /sys/block/md5/md/journal_mode > > Test writes to the RAID-5 via dd: > > $ sudo dd if=/dev/zero of=/dev/md5 iflag=fullblock oflag=direct bs=1M > count=10240 > > ------------------------ observed behavior -------------------------- > Writes proceded at 100 +/- 4 MB/sec to the journal disks. > Writes proceded at 29 +/- 1 MB/sec to the RAID-5 member devices. > This lasted for 50 +/1 1 second, at which point writes stopped and the > kernel printed an error: > BUG: kernel NULL pointer dereference, address: 0000000000000157
If possible can you verify the issue is still present in either the newest 6.4.y upstream or mainline (or nearest to that, the 6.5~rc4-1~exp1 in experimental)? If so can you report the issue upstream and link back here the upstream report? Regards, Salvatore