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

[Jeff Mahoney <jeffm@suse.com>]

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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
>> -- 
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>>
>>   
> 


- -- 
Jeff Mahoney
SUSE Labs
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