Re: Problems with the max value for create directory

[Andreas Dilger <adilger@sun.com>]

On Dec 23, 2008  13:02 +0900, Toshiyuki Okajima wrote:
> Zhang Xiliang wrote:
>> Hi,
>>
>> I creat 65537 long directories and failed when the block size is 1024.
>>
>> # mkfs.ext4dev -b 1024 -I 256 /dev/hda3
>> # tune2fs -E test_fs -O extents /dev/hda3
>> # mount -t ext4dev /dev/hda3 /mnt
>> # ./create_long_dirs 65537 /mnt
>>
>> The code of create_long_dirs.c:
>
> ext4 filesystem cannot make over 65000 links toward a file.
> (ext3 filesystem cannot make over 32000 links toward a file.)
> This test makes over 65000 links toward /mnt-directory.
> (Creating 65000 sub-directories makes 65000 links toward /mnt-directory.)

Note that there is a specific reason why it was implemented this way:
- a directory with > 65000 subdirectories can be checked if empty even
  if the link count is wrong (in fact link count was ignored even in ext3)
- a file needs to keep accurate link counts or it is impossible to know
  when the file needs to be deleted.

We thought about adding a "i_links_count_hi" but it wasn't thought that
many (any) real applications would create so many hard links on the same
file.


Cheers, Andreas
--
Andreas Dilger
Sr. Staff Engineer, Lustre Group
Sun Microsystems of Canada, Inc.