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Re: [PATCH] xfs: be honest about used inodes in statfs

To: Brian Foster <bfoster@xxxxxxxxxx>, Eric Sandeen <sandeen@xxxxxxxxxx>
Subject: Re: [PATCH] xfs: be honest about used inodes in statfs
From: Eric Sandeen <sandeen@xxxxxxxxxxx>
Date: Mon, 24 Feb 2014 14:38:18 -0600
Cc: xfs-oss <xfs@xxxxxxxxxxx>
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <20140224160047.GA13221@xxxxxxxxxxxxxxx>
References: <53067DC0.9040800@xxxxxxxxxx> <20140224160047.GA13221@xxxxxxxxxxxxxxx>
User-agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.9; rv:24.0) Gecko/20100101 Thunderbird/24.3.0
On 2/24/14, 10:01 AM, Brian Foster wrote:
> On Thu, Feb 20, 2014 at 04:12:16PM -0600, Eric Sandeen wrote:
>> Because we have lazy counters, it's possible that we over-allocate
>> inodes past the maxicount (imaxpct) limit.  
>>
>> A previous commit,
>>
>>  2fe3366 xfs: ensure f_ffree returned by statfs() is non-negative
>>
>> stopped statfs from underflowing f_ffree in this case, but that
>> only happened when we mis-reported f_files, capped at maxicount.
>>
>> Change statfs to report the actual number of inodes allocated,
>> even if it is greater than maxicount.  It's reality.
>> Deal with it.  ;)
>>
>> Signed-off-by: Eric Sandeen <sandeen@xxxxxxxxxx>
>> ---
>>
>> diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c
>> index f317488..7c7a810 100644
>> --- a/fs/xfs/xfs_super.c
>> +++ b/fs/xfs/xfs_super.c
>> @@ -1083,7 +1083,6 @@ xfs_fs_statfs(
>>      struct xfs_inode        *ip = XFS_I(dentry->d_inode);
>>      __uint64_t              fakeinos, id;
>>      xfs_extlen_t            lsize;
>> -    __int64_t               ffree;
>>  
>>      statp->f_type = XFS_SB_MAGIC;
>>      statp->f_namelen = MAXNAMELEN - 1;
>> @@ -1100,17 +1099,24 @@ xfs_fs_statfs(
>>      statp->f_blocks = sbp->sb_dblocks - lsize;
>>      statp->f_bfree = statp->f_bavail =
>>                              sbp->sb_fdblocks - XFS_ALLOC_SET_ASIDE(mp);
>> +
>> +    /* Potential number of new inodes in free blocks */
>>      fakeinos = statp->f_bfree << sbp->sb_inopblog;
>> +    /* Total possible files is current inodes + potential new inodes */
>>      statp->f_files =
>>          MIN(sbp->sb_icount + fakeinos, (__uint64_t)XFS_MAXINUMBER);
>> +    /* Unless we have maxicount!  Then cap it at that */
>>      if (mp->m_maxicount)
>>              statp->f_files = min_t(typeof(statp->f_files),
>>                                      statp->f_files,
>>                                      mp->m_maxicount);
>>  
>> -    /* make sure statp->f_ffree does not underflow */
>> -    ffree = statp->f_files - (sbp->sb_icount - sbp->sb_ifree);
>> -    statp->f_ffree = max_t(__int64_t, ffree, 0);
>> +    /* But if we already managed to allocate more, let's be honest */
>> +    statp->f_files = max_t(typeof(statp->f_files),
>> +                            sbp->sb_icount,
>> +                            statp->f_files);
>> +
>> +    statp->f_ffree = statp->f_files - (sbp->sb_icount - sbp->sb_ifree);
> 
> Hi Eric,
> 
> Would something like the following be equivalent (and accurate?):
> 
>         /*
>          * Potential number of new inodes in free blocks, limited by 
> maxicount.
>          */
>         fakeinos = statp->f_bfree << sbp->sb_inopblog;
>         if (mp->m_maxicount)
>                 fakeinos = mp->m_maxicount > sbp->sb_icount ?
>                         MIN(mp->m_maxicount - sbp->sb_icount, fakeinos) : 0;
>         /* Total possible files is current inodes + potential new inodes */
>         statp->f_files = MIN(sbp->sb_icount + fakeinos,
>                                 (__uint64_t) XFS_MAXINUMBER);
> 
>         statp->f_ffree = statp->f_files - (sbp->sb_icount - sbp->sb_ifree);

Yeah, I think that's better.  Want to send that patch?  You did the hard work of
making it look sane.  ;)

-Eric

> Brian
> 
>>  
>>      spin_unlock(&mp->m_sb_lock);
>>  
>>
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> 
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