Hi,
In btrfs, inode number is increased each time a new file or directory
is made.
Therefore, if the making deletion of the file is repeated, value of
'i_ino' increases rapidly.
For example, inode number changes as follows.
$ touch foo
$ ls -i foo
266 foo
$ rm foo
$ touch bar
$ ls -i bar
267 bar
$
And then, length of 'i_ino' and 'objectid' is as follows on the x86
system.
unsigned long i_ino == 32bits
u64 objectid == 64bits
Therefore, in the operation to substitute 'objectid' to 'i_ino',
'i_ino' overflows when 'objectid' 4294967296 is substituted to 'i_ino'.
Then, the file with inode number 0 is made.
As a result, ls command has looped infinitely, and btrfsck detected the
error.
Please see below.
$ uname -a
Linux luna 2.6.37-rc5 #1 SMP Thu Dec 9 13:02:41 JST 2010 i686 i686 i386
GNU/Linux
$ df -T /test1
Filesystem Type 1K-blocks Used Available Use% Mounted on
/dev/sdd14 btrfs 4162560 56 3717632 1% /test1
$ strace -FfTttx ls /test1
14:03:10.115440 execve("/bin/ls", ["ls", "/test1"], [/* 28 vars */]) = 0
<0.000181>
...
...
14:03:10.123431 stat("/test1", {st_mode=S_IFDIR|0777, st_size=8, ...}) = 0
<0.000017>
14:03:10.123521 open("/test1", O_RDONLY|O_NONBLOCK|O_DIRECTORY|O_CLOEXEC) = 3
<0.000018>
14:03:10.123578 fcntl(3, F_GETFD) = 0x1 (flags FD_CLOEXEC) <0.000013>
14:03:10.123637 getdents(3, /* 3 entries */, 32768) = 72 <0.000025>
14:03:10.123712 getdents(3, /* 1 entries */, 32768) = 24 <0.000016>
14:03:10.123768 getdents(3, /* 1 entries */, 32768) = 24 <0.000015>
14:03:10.123824 getdents(3, /* 1 entries */, 32768) = 24 <0.000015>
14:03:10.123880 getdents(3, /* 1 entries */, 32768) = 24 <0.000015>
14:03:10.123936 getdents(3, /* 1 entries */, 32768) = 24 <0.000014>
14:03:10.123992 getdents(3, /* 1 entries */, 32768) = 24 <0.000015>
14:03:10.124047 getdents(3, /* 1 entries */, 32768) = 24 <0.000015>
14:03:10.124103 getdents(3, /* 1 entries */, 32768) = 24 <0.000015>
14:03:10.124261 getdents(3, /* 1 entries */, 32768) = 24 <0.000016>
14:03:10.124320 getdents(3, /* 1 entries */, 32768) = 24 <0.000015>
14:03:10.124381 getdents(3, /* 1 entries */, 32768) = 24 <0.000015>
14:03:10.124437 getdents(3, /* 1 entries */, 32768) = 24 <0.000014>
14:03:10.124493 getdents(3, /* 1 entries */, 32768) = 24 <0.000014>
14:03:10.124549 getdents(3, /* 1 entries */, 32768) = 24 <0.000014>
14:03:10.124605 getdents(3, /* 1 entries */, 32768) = 24 <0.000014>
14:03:10.124661 getdents(3, /* 1 entries */, 32768) = 24 <0.000014>
14:03:10.124717 getdents(3, /* 1 entries */, 32768) = 24 <0.000014>
14:03:10.124773 getdents(3, /* 1 entries */, 32768) = 24 <0.000014>
14:03:10.124840 getdents(3, /* 1 entries */, 32768) = 24 <0.000014>
14:03:10.124896 getdents(3, /* 1 entries */, 32768) = 24 <0.000014>
...
...
$ cd /test1
$ ls -i A123
ls: cannot access A123: No such file or directory
$ touch aaaa
$ ls -i aaaa
1 aaaa
$
# umount /test1
# btrfsck /dev/sdd14
root 5 inode 0 errors 2001
unresolved ref dir 256 index 4294967041 namelen 4 name A123 filetype
1 error 4
root 5 inode 1 errors 2001
unresolved ref dir 256 index 4294967042 namelen 4 name aaaa filetype
1 error 4
root 5 inode 4294967296 errors 2000
unresolved ref dir 256 index 4294967041 namelen 4 name A123 filetype
0 error 3
root 5 inode 4294967297 errors 2000
unresolved ref dir 256 index 4294967042 namelen 4 name aaaa filetype
0 error 3
found 28672 bytes used err is 1
total csum bytes: 0
total tree bytes: 28672
total fs tree bytes: 8192
btree space waste bytes: 23191
file data blocks allocated: 0
referenced 0
Btrfs v0.19-36-g70c6c10
#
Regards,
Itoh
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