[3.4-rc1] attempt to access beyond end of device and livelock

[Daniel J Blueman]

Hi Josef, Chris,

When testing BTRFS with RAID 0 metadata on linux-3.4-rc1, we see
discard ranges exceeding the end of the block device [1], potentially
causing dataloss; when this occurs, filesystem writeback becomes
catatonic due to continual resubmission.

Simply mounting with discard a raid0 metadata filesystem and copying
some data in [2] provokes the issue.

Thanks,
 Daniel

--- [1]

attempt to access beyond end of device
ram0: rw=129, want=8452072, limit=4096000
...

--- [2]

modprobe brd rd_size=2048000 (or boot with ramdisk_size=2048000)
mkfs.btrfs -m raid0 /dev/ram0 /dev/ram1
mount /dev/ram0 /mnt -o discard
cd /mnt && tar -xvzf linux.tar.gz
<access beyond end of device and livelock>
-- 
Daniel J Blueman
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