Re: [PATCH RESUBMIT] reiserfs: Remove 2 TB file size limit

[Edward Shishkin <edward.shishkin@gmail.com>]

Leonardo Chiquitto wrote:
> On Fri, May 21, 2010 at 10:17 AM, Tim Shearouse <t.shearouse@gmail.com> wrote:
>   
>> On Thu, May 20, 2010 at 2:10 PM, Jeff Mahoney <jeffm@suse.com> wrote:
>>     
>>> -----BEGIN PGP SIGNED MESSAGE-----
>>> Hash: SHA1
>>>
>>> On 05/19/2010 06:00 PM, Edward Shishkin wrote:
>>>       
>>>> Leonardo Chiquitto wrote:
>>>>         
>>>>> On Wed, May 19, 2010 at 4:22 PM, Jeff Mahoney <jeffm@suse.com> wrote:
>>>>>
>>>>>           
>>>>>>  In its early life, reiserfs had an evolving s_max_bytes. It started out
>>>>>>  at 4 GB, then was raised to MAX_LFS_FILESIZE, then dropped to 2 TiB
>>>>>> when
>>>>>>  it was observed that struct stat only had a 32-bit st_blocks field.
>>>>>>
>>>>>>  Since then, both the kernel and glibc have evolved as well and now both
>>>>>>  support 64-bit st_blocks. Applications that can't deal with these
>>>>>> ranges
>>>>>>  are assumed to be "legacy" or "broken." File systems now routinely
>>>>>>  support file sizes much larger than can be represented by 2^32 * 512.
>>>>>>
>>>>>>  But we never revisited that limitation. ReiserFS has always been
>>>>>> able to
>>>>>>  support larger file sizes (up to 16 TiB, in fact), but the s_max_bytes
>>>>>>  limitation has prevented that.
>>>>>>
>>>>>>  This patch adds a max_file_offset helper to set s_max_bytes to a more
>>>>>>  appropriate value. I noticed that XFS adjusts the limit based on the
>>>>>>  CPU but I'd prefer to err on the side of compatibility and place the
>>>>>>  limit at the smaller of the 32-bit MAX_LFS_FILESIZE and the maximum
>>>>>>  supported by the file system. At a 4k block size, this is conveniently
>>>>>>  also the advertised maximum file size of reiserfs.
>>>>>>
>>>>>>  Update: This version properly extends PAGE_SIZE_CACHE so the math works
>>>>>>         on 32-bit systems.
>>>>>>
>>>>>>  This bug is tracked at:
>>>>>> https://bugzilla.novell.com/show_bug.cgi?id=592100
>>>>>>
>>>>>> Signed-off-by: Jeff Mahoney <jeffm@suse.com>
>>>>>> - ---
>>>>>>  fs/reiserfs/super.c |   17 +++++++++++++----
>>>>>>  1 file changed, 13 insertions(+), 4 deletions(-)
>>>>>>
>>>>>> - --- a/fs/reiserfs/super.c
>>>>>> +++ b/fs/reiserfs/super.c
>>>>>> @@ -1309,6 +1309,18 @@ out_err:
>>>>>>        return err;
>>>>>>  }
>>>>>>  +static inline loff_t
>>>>>> +reiserfs_max_file_offset(struct super_block *sb)
>>>>>> +{
>>>>>> +       /* Limited by stat_data->sd_blocks, 2^32-1 blocks */
>>>>>> +       loff_t fs_max = ((u64)sb->s_blocksize << 32) - sb->s_blocksize;
>>>>>> +
>>>>>> +       /* Limited by 32-bit MAX_LFS_FILESIZE */
>>>>>> +       loff_t page_cache_max = (((u64)PAGE_CACHE_SIZE << 31)-1);
>>>>>> +
>>>>>> +       return min(fs_max, page_cache_max);
>>>>>> +}
>>>>>> +
>>>>>>  static int read_super_block(struct super_block *s, int offset)
>>>>>>  {
>>>>>>        struct buffer_head *bh;
>>>>>> @@ -1398,10 +1410,7 @@ static int read_super_block(struct super
>>>>>>        s->dq_op = &reiserfs_quota_operations;
>>>>>>  #endif
>>>>>>  -      /* new format is limited by the 32 bit wide i_blocks field,
>>>>>> want to
>>>>>> - -      ** be one full block below that.
>>>>>> - -      */
>>>>>> - -     s->s_maxbytes = (512LL << 32) - s->s_blocksize;
>>>>>> +       s->s_maxbytes = reiserfs_max_file_offset(s);
>>>>>>        return 0;
>>>>>>  }
>>>>>>
>>>>>>             
>>>>> Hello ReiserFS developers,
>>>>>
>>>>> Any chance to have this patch submitted to 2.6.35?
>>>>>           
>>>> I wouldn't rely on this. Reiserfsprogs also should be aware
>>>> of the new limits. It's all long..
>>>>         
>>> I certainly hope not. Things would be broken already. The 2 TB limit is
>>> 2048 * 2^32.
>>>
>>> - -Jeff
>>>
>>>       
>>>>>  We're hitting the 2TB
>>>>> file limit here and this patch resolves the problem.
>>>>>
>>>>> Thanks,
>>>>> Leonardo
>>>>>           
>>> - --
>>> Jeff Mahoney
>>> SUSE Labs
>>>       
>> I do not believe this patch will cause problems. As you mention,
>> ReiserFS was intended to support a max 16TB filesize.
>>
>> Edward, it looks to me as though reiserfsprogs will be aware of the
>> new limits, unless I am missing something (it does not have its own
>> method for accessing the super block somewhere, correct?).
>>     
>
> Hello,
>
> I apologize for insisting here but it's really important for us to get
> this fixed upstream. Please, can someone submit it for 2.6.35

I guess nobody will accept this to 2.6.35..
We only can push it to -mm with the following proceeding
from the akpm's side..

>  or,
> if the patch is not a good idea, give a little insight on what's wrong?
>   

Jeff, did you have any chances to run and fsck this on 32 and 64-bit 
machines?

Thanks,
Edward.