On 2018/9/14 下午1:52, Nikolay Borisov wrote:
>
>
> On 14.09.2018 02:17, Qu Wenruo wrote:
>>
>>
>> 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.
>
> So Qu,
>
> I'm not seeing any EPERM errors, though I see the following so you might
> be right:
>
> openat(AT_FDCWD, "/dev/sdb1", O_RDWR) = 5
>
> followed by a lot of preads, the last one of which is:
>
> pread64(5, 0x557a0abd10b0, 4096, 2732765184) = -1 EIO (Input/output
> error)
Would you please provide the full log?
This pread() looks like some data read.
But without context, it's a little hard to say.
Thanks,
Qu
>
> This is then followed by a a lot of pwrites, the last 10 or so syscalls
> are:
>
> pwrite64(5, "\220\255\262\244\0\0\0\0\0\0"..., 16384, 91127808) = 16384
>
> pwrite64(5, "|IO\233\0\0\0\0\0\0"..., 16384, 91144192) = 16384
>
> pwrite64(5, "x\2501n\0\0\0\0\0\0"..., 16384, 91160576) = 16384
>
> pwrite64(5, "\252\254l)\0\0\0\0\0\0"..., 16384, 91176960) = 16384
>
> pwrite64(5, "P\256\331\373\0\0\0\0\0\0"..., 16384, 91193344) = 16384
>
> pwrite64(5, "\3\230\230+\0\0\0\0\0\0"..., 4096, 83951616) = 4096
>
> write(2, "ERROR: ", 7) = 7
>
> write(2, "failed to "..., 37) = 37
>
> write(2, "\n", 1) = 1
>
> close(4) = 0
>
> write(2, "WARNING: ", 9) = 9
>
> write(2, "an error o"..., 104) = 104
>
> write(2, "\n", 1) = 1
>
> exit_group(1) = ?
>
> but looking at migrate_super_block it's not doing that many writes -
> just writing the sb at BTRFS_SUPER_INFO_OFFSET and then zeroing out
> 0..BTRFS_SUPER_INFO_OFFSET. Also the number of pwrites:
> grep -c pwrite ~/Downloads/btrfs-issue/convert-strace.log
> 198
>
> So the failure is not originating from migrate_super_block.
>
>>
>> Thanks,
>> Qu
>>
