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 >>
