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[PATCH V3] xfs: be honest about used inodes in statfs

To: Eric Sandeen <sandeen@xxxxxxxxxx>, xfs-oss <xfs@xxxxxxxxxxx>
Subject: [PATCH V3] xfs: be honest about used inodes in statfs
From: Eric Sandeen <sandeen@xxxxxxxxxxx>
Date: Mon, 24 Feb 2014 18:15:54 -0600
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <53067DC0.9040800@xxxxxxxxxx>
References: <53067DC0.9040800@xxxxxxxxxx>
User-agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.9; rv:24.0) Gecko/20100101 Thunderbird/24.3.0
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.  

Also rework code & rename vars for clarity after input from
dchinner & bfoster.

Signed-off-by: Eric Sandeen <sandeen@xxxxxxxxxx>
---

V2: code cleanup thanks to Brian
V3: more cleanup thanks to Dave

diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c
index f317488..2f80923 100644
--- a/fs/xfs/xfs_super.c
+++ b/fs/xfs/xfs_super.c
@@ -1081,9 +1081,8 @@ xfs_fs_statfs(
        struct xfs_mount        *mp = XFS_M(dentry->d_sb);
        xfs_sb_t                *sbp = &mp->m_sb;
        struct xfs_inode        *ip = XFS_I(dentry->d_inode);
-       __uint64_t              fakeinos, id;
+       __uint64_t              potential, id;
        xfs_extlen_t            lsize;
-       __int64_t               ffree;
 
        statp->f_type = XFS_SB_MAGIC;
        statp->f_namelen = MAXNAMELEN - 1;
@@ -1100,17 +1099,17 @@ xfs_fs_statfs(
        statp->f_blocks = sbp->sb_dblocks - lsize;
        statp->f_bfree = statp->f_bavail =
                                sbp->sb_fdblocks - XFS_ALLOC_SET_ASIDE(mp);
-       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);
-
-       /* 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);
+
+       /* Potential new inodes in free blocks, limited by maxicount */
+       potential = statp->f_bfree << sbp->sb_inopblog;
+       if (mp->m_maxicount > sbp->sb_icount)
+               potential = min(mp->m_maxicount - sbp->sb_icount, potential);
+       else
+               potential = 0;
+
+       /* Total possible files is current inodes + potential new inodes */
+       statp->f_files = min_t(u64, sbp->sb_icount + potential, XFS_MAXINUMBER);
+       statp->f_ffree = statp->f_files - (sbp->sb_icount - sbp->sb_ifree);
 
        spin_unlock(&mp->m_sb_lock);
 

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