xfs: use generic percpu counters for free inode counter

XFS has hand-rolled per-cpu counters for the superblock since before
there was any generic implementation. The free inode counter is not
used for any limit enforcement - the per-AG free inode counters are
used during allocation to determine if there are inode available for
allocation.

Hence we don't need any of the complexity of the hand-rolled
counters and we can simply replace them with generic per-cpu
counters similar to the inode counter.

This version introduces a xfs_mod_ifree() helper function from
Christoph Hellwig.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>

6 files changed, 42 insertions, 48 deletions

diff --git a/fs/xfs/libxfs/xfs_sb.c b/fs/xfs/libxfs/xfs_sb.c
index 017cb2fc53eb..b66aeab99cfb 100644
--- a/fs/xfs/libxfs/xfs_sb.c
+++ b/fs/xfs/libxfs/xfs_sb.c
@@ -772,6 +772,7 @@ xfs_log_sb(
         struct xfs_buf          *bp = xfs_trans_getsb(tp, mp, 0);
 
         mp->m_sb.sb_icount = percpu_counter_sum(&mp->m_icount);
+        mp->m_sb.sb_ifree = percpu_counter_sum(&mp->m_ifree);
 
         xfs_sb_to_disk(XFS_BUF_TO_SBP(bp), &mp->m_sb);
         xfs_trans_buf_set_type(tp, bp, XFS_BLFT_SB_BUF);
diff --git a/fs/xfs/xfs_fsops.c b/fs/xfs/xfs_fsops.c
index b87a6f92263b..a1ca9c2b8c00 100644
--- a/fs/xfs/xfs_fsops.c
+++ b/fs/xfs/xfs_fsops.c
@@ -639,11 +639,11 @@ xfs_fs_counts(
 {
         xfs_icsb_sync_counters(mp, XFS_ICSB_LAZY_COUNT);
         cnt->allocino = percpu_counter_read_positive(&mp->m_icount);
+        cnt->freeino = percpu_counter_read_positive(&mp->m_ifree);
 
         spin_lock(&mp->m_sb_lock);
         cnt->freedata = mp->m_sb.sb_fdblocks - XFS_ALLOC_SET_ASIDE(mp);
         cnt->freertx = mp->m_sb.sb_frextents;
-        cnt->freeino = mp->m_sb.sb_ifree;
         spin_unlock(&mp->m_sb_lock);
         return 0;
 }
diff --git a/fs/xfs/xfs_mount.c b/fs/xfs/xfs_mount.c
index 702ea6a7e648..650e8f18cd2a 100644
--- a/fs/xfs/xfs_mount.c
+++ b/fs/xfs/xfs_mount.c
@@ -1114,6 +1114,20 @@ xfs_mod_icount(
         return 0;
 }
 
+
+int
+xfs_mod_ifree(
+        struct xfs_mount        *mp,
+        int64_t                 delta)
+{
+        percpu_counter_add(&mp->m_ifree, delta);
+        if (percpu_counter_compare(&mp->m_ifree, 0) < 0) {
+                ASSERT(0);
+                percpu_counter_add(&mp->m_ifree, -delta);
+                return -EINVAL;
+        }
+        return 0;
+}
 /*
  * xfs_mod_incore_sb_unlocked() is a utility routine commonly used to apply
  * a delta to a specified field in the in-core superblock.  Simply
@@ -1142,17 +1156,9 @@ xfs_mod_incore_sb_unlocked(
          */
         switch (field) {
         case XFS_SBS_ICOUNT:
-                ASSERT(0);
-                return -ENOSPC;
         case XFS_SBS_IFREE:
-                lcounter = (long long)mp->m_sb.sb_ifree;
-                lcounter += delta;
-                if (lcounter < 0) {
-                        ASSERT(0);
-                        return -EINVAL;
-                }
-                mp->m_sb.sb_ifree = lcounter;
-                return 0;
+                ASSERT(0);
+                return -EINVAL;
         case XFS_SBS_FDBLOCKS:
                 lcounter = (long long)
                         mp->m_sb.sb_fdblocks - XFS_ALLOC_SET_ASIDE(mp);
@@ -1502,7 +1508,6 @@ xfs_icsb_cpu_notify(
         case CPU_ONLINE:
         case CPU_ONLINE_FROZEN:
                 xfs_icsb_lock(mp);
-                xfs_icsb_balance_counter(mp, XFS_SBS_IFREE, 0);
                 xfs_icsb_balance_counter(mp, XFS_SBS_FDBLOCKS, 0);
                 xfs_icsb_unlock(mp);
                 break;
@@ -1513,15 +1518,12 @@ xfs_icsb_cpu_notify(
                  * re-enable the counters. */
                 xfs_icsb_lock(mp);
                 spin_lock(&mp->m_sb_lock);
-                xfs_icsb_disable_counter(mp, XFS_SBS_IFREE);
                 xfs_icsb_disable_counter(mp, XFS_SBS_FDBLOCKS);
 
-                mp->m_sb.sb_ifree += cntp->icsb_ifree;
                 mp->m_sb.sb_fdblocks += cntp->icsb_fdblocks;
 
                 memset(cntp, 0, sizeof(xfs_icsb_cnts_t));
 
-                xfs_icsb_balance_counter_locked(mp, XFS_SBS_IFREE, 0);
                 xfs_icsb_balance_counter_locked(mp, XFS_SBS_FDBLOCKS, 0);
                 spin_unlock(&mp->m_sb_lock);
                 xfs_icsb_unlock(mp);
@@ -1544,10 +1546,14 @@ xfs_icsb_init_counters(
         if (error)
                 return error;
 
+        error = percpu_counter_init(&mp->m_ifree, 0, GFP_KERNEL);
+        if (error)
+                goto free_icount;
+
         mp->m_sb_cnts = alloc_percpu(xfs_icsb_cnts_t);
         if (!mp->m_sb_cnts) {
-                percpu_counter_destroy(&mp->m_icount);
-                return -ENOMEM;
+                error = -ENOMEM;
+                goto free_ifree;
         }
 
         for_each_online_cpu(i) {
@@ -1570,6 +1576,12 @@ xfs_icsb_init_counters(
 #endif /* CONFIG_HOTPLUG_CPU */
 
         return 0;
+
+free_ifree:
+        percpu_counter_destroy(&mp->m_ifree);
+free_icount:
+        percpu_counter_destroy(&mp->m_icount);
+        return error;
 }
 
 void
@@ -1577,6 +1589,7 @@ xfs_icsb_reinit_counters(
         xfs_mount_t     *mp)
 {
         percpu_counter_set(&mp->m_icount, mp->m_sb.sb_icount);
+        percpu_counter_set(&mp->m_ifree, mp->m_sb.sb_ifree);
 
         xfs_icsb_lock(mp);
         /*
@@ -1584,7 +1597,6 @@ xfs_icsb_reinit_counters(
          * initial balance kicks us off correctly
          */
         mp->m_icsb_counters = -1;
-        xfs_icsb_balance_counter(mp, XFS_SBS_IFREE, 0);
         xfs_icsb_balance_counter(mp, XFS_SBS_FDBLOCKS, 0);
         xfs_icsb_unlock(mp);
 }
@@ -1599,6 +1611,7 @@ xfs_icsb_destroy_counters(
         }
 
         percpu_counter_destroy(&mp->m_icount);
+        percpu_counter_destroy(&mp->m_ifree);
 
         mutex_destroy(&mp->m_icsb_mutex);
 }
@@ -1662,7 +1675,6 @@ xfs_icsb_count(
 
         for_each_online_cpu(i) {
                 cntp = (xfs_icsb_cnts_t *)per_cpu_ptr(mp->m_sb_cnts, i);
-                cnt->icsb_ifree += cntp->icsb_ifree;
                 cnt->icsb_fdblocks += cntp->icsb_fdblocks;
         }
 
@@ -1675,7 +1687,7 @@ xfs_icsb_counter_disabled(
         xfs_mount_t     *mp,
         xfs_sb_field_t  field)
 {
-        ASSERT((field >= XFS_SBS_IFREE) && (field <= XFS_SBS_FDBLOCKS));
+        ASSERT(field == XFS_SBS_FDBLOCKS);
         return test_bit(field, &mp->m_icsb_counters);
 }
 
@@ -1686,7 +1698,7 @@ xfs_icsb_disable_counter(
 {
         xfs_icsb_cnts_t cnt;
 
-        ASSERT((field >= XFS_SBS_IFREE) && (field <= XFS_SBS_FDBLOCKS));
+        ASSERT(field == XFS_SBS_FDBLOCKS);
 
         /*
          * If we are already disabled, then there is nothing to do
@@ -1705,9 +1717,6 @@ xfs_icsb_disable_counter(
 
                 xfs_icsb_count(mp, &cnt, XFS_ICSB_LAZY_COUNT);
                 switch(field) {
-                case XFS_SBS_IFREE:
-                        mp->m_sb.sb_ifree = cnt.icsb_ifree;
-                        break;
                 case XFS_SBS_FDBLOCKS:
                         mp->m_sb.sb_fdblocks = cnt.icsb_fdblocks;
                         break;
@@ -1729,15 +1738,12 @@ xfs_icsb_enable_counter(
         xfs_icsb_cnts_t *cntp;
         int             i;
 
-        ASSERT((field >= XFS_SBS_IFREE) && (field <= XFS_SBS_FDBLOCKS));
+        ASSERT(field == XFS_SBS_FDBLOCKS);
 
         xfs_icsb_lock_all_counters(mp);
         for_each_online_cpu(i) {
                 cntp = per_cpu_ptr(mp->m_sb_cnts, i);
                 switch (field) {
-                case XFS_SBS_IFREE:
-                        cntp->icsb_ifree = count + resid;
-                        break;
                 case XFS_SBS_FDBLOCKS:
                         cntp->icsb_fdblocks = count + resid;
                         break;
@@ -1760,8 +1766,6 @@ xfs_icsb_sync_counters_locked(
 
         xfs_icsb_count(mp, &cnt, flags);
 
-        if (!xfs_icsb_counter_disabled(mp, XFS_SBS_IFREE))
-                mp->m_sb.sb_ifree = cnt.icsb_ifree;
         if (!xfs_icsb_counter_disabled(mp, XFS_SBS_FDBLOCKS))
                 mp->m_sb.sb_fdblocks = cnt.icsb_fdblocks;
 }
@@ -1813,12 +1817,6 @@ xfs_icsb_balance_counter_locked(
 
         /* update counters  - first CPU gets residual*/
         switch (field) {
-        case XFS_SBS_IFREE:
-                count = mp->m_sb.sb_ifree;
-                resid = do_div(count, weight);
-                if (count < max(min, XFS_ICSB_INO_CNTR_REENABLE))
-                        return;
-                break;
         case XFS_SBS_FDBLOCKS:
                 count = mp->m_sb.sb_fdblocks;
                 resid = do_div(count, weight);
@@ -1873,14 +1871,6 @@ again:
         }
 
         switch (field) {
-        case XFS_SBS_IFREE:
-                lcounter = icsbp->icsb_ifree;
-                lcounter += delta;
-                if (unlikely(lcounter < 0))
-                        goto balance_counter;
-                icsbp->icsb_ifree = lcounter;
-                break;
-
         case XFS_SBS_FDBLOCKS:
                 BUG_ON((mp->m_resblks - mp->m_resblks_avail) != 0);
 
diff --git a/fs/xfs/xfs_mount.h b/fs/xfs/xfs_mount.h
index 76b18c8c58c5..7ce997d43d81 100644
--- a/fs/xfs/xfs_mount.h
+++ b/fs/xfs/xfs_mount.h
@@ -84,6 +84,7 @@ typedef struct xfs_mount {
         struct xfs_sb           m_sb;           /* copy of fs superblock */
         spinlock_t              m_sb_lock;      /* sb counter lock */
         struct percpu_counter   m_icount;       /* allocated inodes counter */
+        struct percpu_counter   m_ifree;        /* free inodes counter */
 
         struct xfs_buf          *m_sb_bp;       /* buffer for superblock */
         char                    *m_fsname;      /* filesystem name */
@@ -391,6 +392,7 @@ extern int	xfs_mod_incore_sb(xfs_mount_t *, xfs_sb_field_t, int64_t, int);
 extern int      xfs_mod_incore_sb_batch(xfs_mount_t *, xfs_mod_sb_t *,
                         uint, int);
 extern int      xfs_mod_icount(struct xfs_mount *mp, int64_t delta);
+extern int      xfs_mod_ifree(struct xfs_mount *mp, int64_t delta);
 extern int      xfs_mount_log_sb(xfs_mount_t *);
 extern struct xfs_buf *xfs_getsb(xfs_mount_t *, int);
 extern int      xfs_readsb(xfs_mount_t *, int);
diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c
index 0aa4428bfa31..049147776ee1 100644
--- a/fs/xfs/xfs_super.c
+++ b/fs/xfs/xfs_super.c
@@ -1086,6 +1086,7 @@ xfs_fs_statfs(
         struct xfs_inode        *ip = XFS_I(dentry->d_inode);
         __uint64_t              fakeinos, id;
         __uint64_t              icount;
+        __uint64_t              ifree;
         xfs_extlen_t            lsize;
         __int64_t               ffree;
 
@@ -1098,6 +1099,7 @@ xfs_fs_statfs(
 
         xfs_icsb_sync_counters(mp, XFS_ICSB_LAZY_COUNT);
         icount = percpu_counter_sum(&mp->m_icount);
+        ifree = percpu_counter_sum(&mp->m_ifree);
 
         spin_lock(&mp->m_sb_lock);
         statp->f_bsize = sbp->sb_blocksize;
@@ -1118,7 +1120,7 @@ xfs_fs_statfs(
                                         sbp->sb_icount);
 
         /* make sure statp->f_ffree does not underflow */
-        ffree = statp->f_files - (icount - sbp->sb_ifree);
+        ffree = statp->f_files - (icount - ifree);
         statp->f_ffree = max_t(__int64_t, ffree, 0);
 
         spin_unlock(&mp->m_sb_lock);
diff --git a/fs/xfs/xfs_trans.c b/fs/xfs/xfs_trans.c
index 9bc742b65f24..68680ce67547 100644
--- a/fs/xfs/xfs_trans.c
+++ b/fs/xfs/xfs_trans.c
@@ -560,8 +560,7 @@ xfs_trans_unreserve_and_mod_sb(
         }
 
         if (ifreedelta) {
-                error = xfs_icsb_modify_counters(mp, XFS_SBS_IFREE,
-                                                 ifreedelta, rsvd);
+                error = xfs_mod_ifree(mp, ifreedelta);
                 if (error)
                         goto out_undo_icount;
         }
@@ -630,7 +629,7 @@ xfs_trans_unreserve_and_mod_sb(
 
 out_undo_ifreecount:
         if (ifreedelta)
-                xfs_icsb_modify_counters(mp, XFS_SBS_IFREE, -ifreedelta, rsvd);
+                xfs_mod_ifree(mp, -ifreedelta);
 out_undo_icount:
         if (idelta)
                 xfs_mod_icount(mp, -idelta);