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[PATCH 2/7] xfs: use generic percpu counters for free inode counter

To: xfs@xxxxxxxxxxx
Subject: [PATCH 2/7] xfs: use generic percpu counters for free inode counter
From: Dave Chinner <david@xxxxxxxxxxxxx>
Date: Thu, 5 Feb 2015 07:54:04 +1100
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <1423083249-27493-1-git-send-email-david@xxxxxxxxxxxxx>
References: <1423083249-27493-1-git-send-email-david@xxxxxxxxxxxxx>
From: Dave Chinner <dchinner@xxxxxxxxxx>

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@xxxxxxxxxx>
---
 fs/xfs/libxfs/xfs_sb.c |  1 +
 fs/xfs/xfs_fsops.c     |  2 +-
 fs/xfs/xfs_mount.c     | 76 ++++++++++++++++++++++----------------------------
 fs/xfs/xfs_mount.h     |  2 ++
 fs/xfs/xfs_super.c     |  4 ++-
 fs/xfs/xfs_trans.c     |  5 ++--
 6 files changed, 42 insertions(+), 48 deletions(-)

diff --git a/fs/xfs/libxfs/xfs_sb.c b/fs/xfs/libxfs/xfs_sb.c
index 017cb2f..b66aeab 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 e1470f2..fa74d03 100644
--- a/fs/xfs/xfs_fsops.c
+++ b/fs/xfs/xfs_fsops.c
@@ -632,11 +632,11 @@ 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 702ea6a..650e8f1 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 457c6e3..0cb32ce 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 */
@@ -380,6 +381,7 @@ 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 87e169f..e06aa6b 100644
--- a/fs/xfs/xfs_super.c
+++ b/fs/xfs/xfs_super.c
@@ -1088,6 +1088,7 @@ 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;
 
@@ -1100,6 +1101,7 @@ 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;
@@ -1115,7 +1117,7 @@ xfs_fs_statfs(
                                        mp->m_maxicount);
 
        /* 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 9bc742b..68680ce 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);
-- 
2.0.0

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