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) 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 >
