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

[Leonardo Chiquitto <leonardo.lists@gmail.com>]

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

Thanks,
Leonardo
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