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Re: [PATCH V2] xfs: be honest about used inodes in statfs

To: Eric Sandeen <sandeen@xxxxxxxxxxx>
Subject: Re: [PATCH V2] xfs: be honest about used inodes in statfs
From: Brian Foster <bfoster@xxxxxxxxxx>
Date: Mon, 24 Feb 2014 18:55:12 -0500
Cc: Eric Sandeen <sandeen@xxxxxxxxxx>, xfs-oss <xfs@xxxxxxxxxxx>
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <530BD167.2020600@xxxxxxxxxxx>
References: <53067DC0.9040800@xxxxxxxxxx> <530BD167.2020600@xxxxxxxxxxx>
User-agent: Mutt/1.5.21 (2010-09-15)
On Mon, Feb 24, 2014 at 05:10:31PM -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.  
> 
> (New clearer code flow thanks to Brian!)
> 
> Logic-made-readable-by: Brian Foster <bfoster@xxxxxxxxxx>
> Signed-off-by: Eric Sandeen <sandeen@xxxxxxxxxx>
> ---
> 

Heh, looks good to me. I don't know if the LMRB tag disqualifies me as a
reviewer now ;), but feel free to replace it with:

Reviewed-by: Brian Foster <bfoster@xxxxxxxxxx>

> V2: Use Brian's suggested logic for working out the numbers
> 
> diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c
> index f317488..0dbcc17 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 +1099,19 @@ 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, limited by maxicount.
> +      */
>       fakeinos = statp->f_bfree << sbp->sb_inopblog;
> -     statp->f_files =
> -         MIN(sbp->sb_icount + fakeinos, (__uint64_t)XFS_MAXINUMBER);
>       if (mp->m_maxicount)
> -             statp->f_files = min_t(typeof(statp->f_files),
> -                                     statp->f_files,
> -                                     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);
>  
> -     /* 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);
> +     statp->f_ffree = statp->f_files - (sbp->sb_icount - sbp->sb_ifree);
>  
>       spin_unlock(&mp->m_sb_lock);
>  
> 
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