Hi, I started a balance of one block group, and I saw this in dmesg:
BTRFS info (device sdi1): balance: start -dvrange=2236714319872..2236714319873 BTRFS info (device sdi1): relocating block group 2236714319872 flags data|raid0 BTRFS info (device sdi1): found 1 extents BTRFS info (device sdi1): found 1 extents BTRFS info (device sdi1): found 1 extents BTRFS info (device sdi1): found 1 extents BTRFS info (device sdi1): found 1 extents It continued like that for a total of 754 lines until I rebooted. Before that, I captured some debug info. I ran this in my shell for a few seconds, where PID is the pid of the process that called the balance ioctl: integer i=0; while true; do sudo cat /proc/PID/stack >stack$i; sleep .01010101; i+=1; done Which effectively gave me stack samples at (close to) 99Hz. Maybe not ideal, but I was in a hurry and I didn't want my disks to sustain such heavy, repetitive I/O for too long. I've attached the stack samples as stacks.tar.gz. A few of them are empty. To me, it looks like the kernel never left the while (1) loop in btrfs_relocate_block_group. The kernel messages seem to confirm this. I am using Arch Linux with kernel version 5.2.14-arch2, and I specified "slub_debug=P,kmalloc-2k" in the kernel cmdline to detect and protect against a use-after-free that I found when I had KASAN enabled. Would that kernel parameter result in a silent retry if it hit the use-after- free? -- Cebtenzzre <cebtenz...@gmail.com>
stacks.tar.gz
Description: application/compressed-tar
