[PATCH V4] xfs: be honest about used inodes in statfs

Eric Sandeen
2014-02-25T00:27:39Z

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@redhat.com>
---

V2: code cleanup thanks to Brian
V3: more cleanup thanks to Dave
V4: Oh for crying out loud... (add maxicount test in else)

diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c
index f317488..02537f4 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 if (mp->m_maxicount)
+ 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);