On 2018/9/14 上午12:37, Nikolay Borisov wrote:
> On 13.09.2018 19:15, Serhat Sevki Dincer wrote:
>>> -1 seems to be EPERM, is your device write-protected, readonly or
>>> something like that ?
>> I am able to use ext4 partition read/write, created a file and wrote
>> in it, un/re mounted it, all is ok.
>> The drive only has a microusb port and a little led light; no rw
>> switch or anything like that..
> What might help is running btrfs convert under strace. So something like :
> sudo strace -f -o strace.log btrfs-convert /dev/sdb1 and then send the log.
strace would greatly help in this case.

My guess is something wrong happened in migrate_super_block(), which
doesn't handle ret > 0 case well.
In that case, it means pwrite 4K doesn't finish in one call, which looks
pretty strange.


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