On Mon, May 29, 2023 at 04:59:40PM -0400, Mikulas Patocka wrote: > Hi > > I improved the dm-flakey device mapper target, so that it can do random > corruption of read and write bios - I uploaded it here: > https://people.redhat.com/~mpatocka/testcases/bcachefs/dm-flakey.c > > I set up dm-flakey, so that it corrupts 10% of read bios and 10% of write > bios with this command: > dmsetup create flakey --table "0 `blockdev --getsize /dev/ram0` flakey /dev/ram0 0 0 1 4 random_write_corrupt 100000000 random_read_corrupt 100000000" > > > I created a bcachefs volume on a single disk (metadata and data checksums > were turned off) and mounted it on dm-flakey. I got: > > crash: https://people.redhat.com/~mpatocka/testcases/bcachefs/crash1.txt > deadlock: https://people.redhat.com/~mpatocka/testcases/bcachefs/crash2.txt > infinite loop: https://people.redhat.com/~mpatocka/testcases/bcachefs/crash3.txt > > Here I uploaded an image that causes infnite loop when we run bcachefs > fsck on it or when we attempt mount it: > https://people.redhat.com/~mpatocka/testcases/bcachefs/inf-loop.gz > > > I tried to run bcachefs on two block devices and fuzzing just one of them > (checksums and replication were turned on - so bcachefs shold correct the > corrupted data) - in this scenario, bcachefs doesn't return invalid data, > but it sometimes returns errors and sometimes crashes. > > This script will trigger an oops on unmount: > https://people.redhat.com/~mpatocka/testcases/bcachefs/crash4.txt > or nonsensical errors returned to userspace: > rm: cannot remove '/mnt/test/test/cmd_migrate.c': Unknown error 2206 > or I/O errors returned to userspace: > diff: /mnt/test/test/rust-src/target/release/.fingerprint/bch_bindgen-f0bad16858ff0019/lib-bch_bindgen.json: Input/output error > > #!/bin/sh -ex > umount /mnt/test || true > dmsetup remove_all || true > rmmod brd || true > SRC=/usr/src/git/bcachefs-tools > while true; do > modprobe brd rd_size=1048576 > bcachefs format --replicas=2 /dev/ram0 /dev/ram1 > dmsetup create flakey --table "0 `blockdev --getsize /dev/ram0` linear /dev/ram0 0" > mount -t bcachefs /dev/mapper/flakey:/dev/ram1 /mnt/test > dmsetup load flakey --table "0 `blockdev --getsize /dev/ram0` flakey /dev/ram0 0 0 1 4 random_write_corrupt 100000000 random_read_corrupt 100000000" Hey, that's really neat! Any chance you'd be willing to get the dm-flakey changes merged into upstream so that someone can write a recoveryloop fstest to test all the filesystems systematically? :D --D > dmsetup suspend flakey > dmsetup resume flakey > cp -a "$SRC" /mnt/test/test > diff -r "$SRC" /mnt/test/test > echo 3 >/proc/sys/vm/drop_caches > diff -r "$SRC" /mnt/test/test > echo 3 >/proc/sys/vm/drop_caches > diff -r "$SRC" /mnt/test/test > echo 3 >/proc/sys/vm/drop_caches > rm -rf /mnt/test/test > echo 3 >/proc/sys/vm/drop_caches > cp -a "$SRC" /mnt/test/test > echo 3 >/proc/sys/vm/drop_caches > diff -r "$SRC" /mnt/test/test > umount /mnt/test > dmsetup remove flakey > rmmod brd > done > > The oops happens in set_btree_iter_dontneed and it is caused by the fact > that iter->path is NULL. The code in try_alloc_bucket is buggy because it > sets "struct btree_iter iter = { NULL };" and then jumps to the "err" > label that tries to dereference values in "iter". > > > Bcachefs gives not much usefull error messages, like "Fatal error: Unknown > error 2184" or "Error in recovery: cannot allocate memory" or "mount(2) > system call failed: Unknown error 2186." or "rm: cannot remove > '/mnt/test/xfstests-dev/tools/fs-walk': Unknown error 2206". > > Mikulas >
