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[PATCH 04/34] xfs: use generic per-cpu counter infrastructure

To: xfs@xxxxxxxxxxx
Subject: [PATCH 04/34] xfs: use generic per-cpu counter infrastructure
From: Dave Chinner <david@xxxxxxxxxxxxx>
Date: Tue, 21 Dec 2010 18:29:00 +1100
In-reply-to: <1292916570-25015-1-git-send-email-david@xxxxxxxxxxxxx>
References: <1292916570-25015-1-git-send-email-david@xxxxxxxxxxxxx>
From: Dave Chinner <dchinner@xxxxxxxxxx>

XFS has a per-cpu counter implementation for in-core superblock
counters that pre-dated the generic implementation. It is complex
and baroque as it is tailored directly to the needs of ENOSPC
detection.

Now that the generic percpu counter infrastructure has the
percpu_counter_add_unless_lt() function that implements the
necessary threshold checks for us, switch the XFS per-cpu
superblock counters to use the generic percpu counter
infrastructure.

Signed-off-by: Dave Chinner <dchinner@xxxxxxxxxx>
Reviewed-by: Christoph Hellwig <hch@xxxxxx>
---
 fs/xfs/linux-2.6/xfs_linux.h |    9 -
 fs/xfs/linux-2.6/xfs_super.c |    4 +-
 fs/xfs/xfs_fsops.c           |    4 +-
 fs/xfs/xfs_mount.c           |  806 ++++++++----------------------------------
 fs/xfs/xfs_mount.h           |   71 +---
 5 files changed, 171 insertions(+), 723 deletions(-)

diff --git a/fs/xfs/linux-2.6/xfs_linux.h b/fs/xfs/linux-2.6/xfs_linux.h
index 214ddd7..9fa4f2a 100644
--- a/fs/xfs/linux-2.6/xfs_linux.h
+++ b/fs/xfs/linux-2.6/xfs_linux.h
@@ -88,15 +88,6 @@
 #include <xfs_super.h>
 #include <xfs_buf.h>
 
-/*
- * Feature macros (disable/enable)
- */
-#ifdef CONFIG_SMP
-#define HAVE_PERCPU_SB /* per cpu superblock counters are a 2.6 feature */
-#else
-#undef  HAVE_PERCPU_SB /* per cpu superblock counters are a 2.6 feature */
-#endif
-
 #define irix_sgid_inherit      xfs_params.sgid_inherit.val
 #define irix_symlink_mode      xfs_params.symlink_mode.val
 #define xfs_panic_mask         xfs_params.panic_mask.val
diff --git a/fs/xfs/linux-2.6/xfs_super.c b/fs/xfs/linux-2.6/xfs_super.c
index c45b323..abcda07 100644
--- a/fs/xfs/linux-2.6/xfs_super.c
+++ b/fs/xfs/linux-2.6/xfs_super.c
@@ -1229,9 +1229,9 @@ xfs_fs_statfs(
        statp->f_fsid.val[0] = (u32)id;
        statp->f_fsid.val[1] = (u32)(id >> 32);
 
-       xfs_icsb_sync_counters(mp, XFS_ICSB_LAZY_COUNT);
-
        spin_lock(&mp->m_sb_lock);
+       xfs_icsb_sync_counters(mp);
+
        statp->f_bsize = sbp->sb_blocksize;
        lsize = sbp->sb_logstart ? sbp->sb_logblocks : 0;
        statp->f_blocks = sbp->sb_dblocks - lsize;
diff --git a/fs/xfs/xfs_fsops.c b/fs/xfs/xfs_fsops.c
index a7c116e..fb9a9c8 100644
--- a/fs/xfs/xfs_fsops.c
+++ b/fs/xfs/xfs_fsops.c
@@ -478,8 +478,8 @@ xfs_fs_counts(
        xfs_mount_t             *mp,
        xfs_fsop_counts_t       *cnt)
 {
-       xfs_icsb_sync_counters(mp, XFS_ICSB_LAZY_COUNT);
        spin_lock(&mp->m_sb_lock);
+       xfs_icsb_sync_counters(mp);
        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;
@@ -540,7 +540,7 @@ xfs_reserve_blocks(
         */
 retry:
        spin_lock(&mp->m_sb_lock);
-       xfs_icsb_sync_counters_locked(mp, 0);
+       xfs_icsb_sync_counters(mp);
 
        /*
         * If our previous reservation was larger than the current value,
diff --git a/fs/xfs/xfs_mount.c b/fs/xfs/xfs_mount.c
index 19e9dfa..4a99e14 100644
--- a/fs/xfs/xfs_mount.c
+++ b/fs/xfs/xfs_mount.c
@@ -46,19 +46,6 @@
 
 STATIC void    xfs_unmountfs_wait(xfs_mount_t *);
 
-
-#ifdef HAVE_PERCPU_SB
-STATIC void    xfs_icsb_balance_counter(xfs_mount_t *, xfs_sb_field_t,
-                                               int);
-STATIC void    xfs_icsb_balance_counter_locked(xfs_mount_t *, xfs_sb_field_t,
-                                               int);
-STATIC void    xfs_icsb_disable_counter(xfs_mount_t *, xfs_sb_field_t);
-#else
-
-#define xfs_icsb_balance_counter(mp, a, b)             do { } while (0)
-#define xfs_icsb_balance_counter_locked(mp, a, b)      do { } while (0)
-#endif
-
 static const struct {
        short offset;
        short type;     /* 0 = integer
@@ -281,6 +268,71 @@ xfs_free_perag(
 }
 
 /*
+ * Per-cpu incore superblock counters
+ *
+ * This provides distributed per cpu counters for contended fields (e.g. free
+ * block count).  Difficulties arise in that the incore sb is used for ENOSPC
+ * checking, and hence needs to be accurately read when we are running low on
+ * space. Hence We need to check against counter error bounds and determine how
+ * accurately to sum based on that metric. The percpu counters take care of
+ * this for us, so we only need to modify the fast path to handle per-cpu
+ * counter error cases.
+ */
+void
+xfs_icsb_reinit_counters(
+       struct xfs_mount        *mp)
+{
+       percpu_counter_set(&mp->m_icsb[XFS_ICSB_FDBLOCKS],
+                                               mp->m_sb.sb_fdblocks);
+       percpu_counter_set(&mp->m_icsb[XFS_ICSB_IFREE], mp->m_sb.sb_ifree);
+       percpu_counter_set(&mp->m_icsb[XFS_ICSB_ICOUNT], mp->m_sb.sb_icount);
+}
+
+int
+xfs_icsb_init_counters(
+       struct xfs_mount        *mp)
+{
+       int                     i;
+       int                     error;
+
+       for (i = 0; i < XFS_ICSB_MAX; i++) {
+               error = percpu_counter_init(&mp->m_icsb[i], 0);
+               if (error)
+                       goto out_error;
+       }
+       xfs_icsb_reinit_counters(mp);
+       return 0;
+
+out_error:
+       for (; i >= 0; i--)
+               percpu_counter_destroy(&mp->m_icsb[i]);
+       return error;
+}
+
+void
+xfs_icsb_destroy_counters(
+       xfs_mount_t     *mp)
+{
+       int             i;
+
+       for (i = 0; i < XFS_ICSB_MAX; i++)
+               percpu_counter_destroy(&mp->m_icsb[i]);
+}
+
+void
+xfs_icsb_sync_counters(
+       xfs_mount_t     *mp)
+{
+       assert_spin_locked(&mp->m_sb_lock);
+       mp->m_sb.sb_icount =
+               percpu_counter_sum_positive(&mp->m_icsb[XFS_ICSB_ICOUNT]);
+       mp->m_sb.sb_ifree =
+               percpu_counter_sum_positive(&mp->m_icsb[XFS_ICSB_IFREE]);
+       mp->m_sb.sb_fdblocks =
+               percpu_counter_sum_positive(&mp->m_icsb[XFS_ICSB_FDBLOCKS]);
+}
+
+/*
  * Check size of device based on the (data/realtime) block count.
  * Note: this check is used by the growfs code as well as mount.
  */
@@ -1562,7 +1614,9 @@ xfs_log_sbcount(
        if (!xfs_fs_writable(mp))
                return 0;
 
-       xfs_icsb_sync_counters(mp, 0);
+       spin_lock(&mp->m_sb_lock);
+       xfs_icsb_sync_counters(mp);
+       spin_unlock(&mp->m_sb_lock);
 
        /*
         * we don't need to do this if we are updating the superblock
@@ -1674,9 +1728,8 @@ xfs_mod_incore_sb_unlocked(
        int64_t         delta,
        int             rsvd)
 {
-       int             scounter;       /* short counter for 32 bit fields */
-       long long       lcounter;       /* long counter for 64 bit fields */
-       long long       res_used, rem;
+       int             scounter = 0;   /* short counter for 32 bit fields */
+       long long       lcounter = 0;   /* long counter for 64 bit fields */
 
        /*
         * With the in-core superblock spin lock held, switch
@@ -1685,66 +1738,6 @@ xfs_mod_incore_sb_unlocked(
         * 0, then do not apply the delta and return EINVAL.
         */
        switch (field) {
-       case XFS_SBS_ICOUNT:
-               lcounter = (long long)mp->m_sb.sb_icount;
-               lcounter += delta;
-               if (lcounter < 0) {
-                       ASSERT(0);
-                       return XFS_ERROR(EINVAL);
-               }
-               mp->m_sb.sb_icount = lcounter;
-               return 0;
-       case XFS_SBS_IFREE:
-               lcounter = (long long)mp->m_sb.sb_ifree;
-               lcounter += delta;
-               if (lcounter < 0) {
-                       ASSERT(0);
-                       return XFS_ERROR(EINVAL);
-               }
-               mp->m_sb.sb_ifree = lcounter;
-               return 0;
-       case XFS_SBS_FDBLOCKS:
-               lcounter = (long long)
-                       mp->m_sb.sb_fdblocks - XFS_ALLOC_SET_ASIDE(mp);
-               res_used = (long long)(mp->m_resblks - mp->m_resblks_avail);
-
-               if (delta > 0) {                /* Putting blocks back */
-                       if (res_used > delta) {
-                               mp->m_resblks_avail += delta;
-                       } else {
-                               rem = delta - res_used;
-                               mp->m_resblks_avail = mp->m_resblks;
-                               lcounter += rem;
-                       }
-               } else {                                /* Taking blocks away */
-                       lcounter += delta;
-                       if (lcounter >= 0) {
-                               mp->m_sb.sb_fdblocks = lcounter +
-                                                       XFS_ALLOC_SET_ASIDE(mp);
-                               return 0;
-                       }
-
-                       /*
-                        * We are out of blocks, use any available reserved
-                        * blocks if were allowed to.
-                        */
-                       if (!rsvd)
-                               return XFS_ERROR(ENOSPC);
-
-                       lcounter = (long long)mp->m_resblks_avail + delta;
-                       if (lcounter >= 0) {
-                               mp->m_resblks_avail = lcounter;
-                               return 0;
-                       }
-                       printk_once(KERN_WARNING
-                               "Filesystem \"%s\": reserve blocks depleted! "
-                               "Consider increasing reserve pool size.",
-                               mp->m_fsname);
-                       return XFS_ERROR(ENOSPC);
-               }
-
-               mp->m_sb.sb_fdblocks = lcounter + XFS_ALLOC_SET_ASIDE(mp);
-               return 0;
        case XFS_SBS_FREXTENTS:
                lcounter = (long long)mp->m_sb.sb_frextents;
                lcounter += delta;
@@ -1846,9 +1839,6 @@ xfs_mod_incore_sb(
 {
        int                     status;
 
-#ifdef HAVE_PERCPU_SB
-       ASSERT(field < XFS_SBS_ICOUNT || field > XFS_SBS_FDBLOCKS);
-#endif
        spin_lock(&mp->m_sb_lock);
        status = xfs_mod_incore_sb_unlocked(mp, field, delta, rsvd);
        spin_unlock(&mp->m_sb_lock);
@@ -1886,9 +1876,6 @@ xfs_mod_incore_sb_batch(
         */
        spin_lock(&mp->m_sb_lock);
        for (msbp = &msbp[0]; msbp < (msb + nmsb); msbp++) {
-               ASSERT(msbp->msb_field < XFS_SBS_ICOUNT ||
-                      msbp->msb_field > XFS_SBS_FDBLOCKS);
-
                error = xfs_mod_incore_sb_unlocked(mp, msbp->msb_field,
                                                   msbp->msb_delta, rsvd);
                if (error)
@@ -1907,6 +1894,90 @@ unwind:
        return error;
 }
 
+int
+xfs_icsb_modify_counters(
+       xfs_mount_t     *mp,
+       xfs_sb_field_t  field,
+       int64_t         delta,
+       int             rsvd)
+{
+       int64_t         lcounter;
+       int64_t         res_used;
+       int             ret = 0;
+
+
+       switch (field) {
+       case XFS_SBS_ICOUNT:
+               ret = percpu_counter_add_unless_lt(&mp->m_icsb[XFS_SBS_ICOUNT],
+                                                       delta, 0);
+               if (ret < 0) {
+                       ASSERT(0);
+                       return XFS_ERROR(EINVAL);
+               }
+               return 0;
+
+       case XFS_SBS_IFREE:
+               ret = percpu_counter_add_unless_lt(&mp->m_icsb[XFS_SBS_IFREE],
+                                                       delta, 0);
+               if (ret < 0) {
+                       ASSERT(0);
+                       return XFS_ERROR(EINVAL);
+               }
+               return 0;
+
+       case XFS_SBS_FDBLOCKS:
+               /*
+                * if we are putting blocks back, put them into the reserve
+                * block pool first.
+                */
+               if (mp->m_resblks != mp->m_resblks_avail && delta > 0) {
+                       spin_lock(&mp->m_sb_lock);
+                       res_used = (int64_t)(mp->m_resblks -
+                                               mp->m_resblks_avail);
+                       if (res_used > delta) {
+                               mp->m_resblks_avail += delta;
+                               delta = 0;
+                       } else {
+                               delta -= res_used;
+                               mp->m_resblks_avail = mp->m_resblks;
+                       }
+                       spin_unlock(&mp->m_sb_lock);
+                       if (!delta)
+                               return 0;
+               }
+
+               /* try the change */
+               ret = 
percpu_counter_add_unless_lt(&mp->m_icsb[XFS_ICSB_FDBLOCKS],
+                                               delta, XFS_ALLOC_SET_ASIDE(mp));
+               if (likely(ret >= 0))
+                       return 0;
+
+               /* ENOSPC */
+               ASSERT(delta < 0);
+
+               if (!rsvd)
+                       return XFS_ERROR(ENOSPC);
+
+               spin_lock(&mp->m_sb_lock);
+               lcounter = (int64_t)mp->m_resblks_avail + delta;
+               if (lcounter >= 0) {
+                       mp->m_resblks_avail = lcounter;
+                       spin_unlock(&mp->m_sb_lock);
+                       return 0;
+               }
+               spin_unlock(&mp->m_sb_lock);
+               printk_once(KERN_WARNING
+                       "Filesystem \"%s\": reserve blocks depleted! "
+                       "Consider increasing reserve pool size.",
+                       mp->m_fsname);
+               return XFS_ERROR(ENOSPC);
+       default:
+               ASSERT(0);
+               return XFS_ERROR(EINVAL);
+       }
+       return 0;
+}
+
 /*
  * xfs_getsb() is called to obtain the buffer for the superblock.
  * The buffer is returned locked and read in from disk.
@@ -2000,572 +2071,3 @@ xfs_dev_is_read_only(
        }
        return 0;
 }
-
-#ifdef HAVE_PERCPU_SB
-/*
- * Per-cpu incore superblock counters
- *
- * Simple concept, difficult implementation
- *
- * Basically, replace the incore superblock counters with a distributed per cpu
- * counter for contended fields (e.g.  free block count).
- *
- * Difficulties arise in that the incore sb is used for ENOSPC checking, and
- * hence needs to be accurately read when we are running low on space. Hence
- * there is a method to enable and disable the per-cpu counters based on how
- * much "stuff" is available in them.
- *
- * Basically, a counter is enabled if there is enough free resource to justify
- * running a per-cpu fast-path. If the per-cpu counter runs out (i.e. a local
- * ENOSPC), then we disable the counters to synchronise all callers and
- * re-distribute the available resources.
- *
- * If, once we redistributed the available resources, we still get a failure,
- * we disable the per-cpu counter and go through the slow path.
- *
- * The slow path is the current xfs_mod_incore_sb() function.  This means that
- * when we disable a per-cpu counter, we need to drain its resources back to
- * the global superblock. We do this after disabling the counter to prevent
- * more threads from queueing up on the counter.
- *
- * Essentially, this means that we still need a lock in the fast path to enable
- * synchronisation between the global counters and the per-cpu counters. This
- * is not a problem because the lock will be local to a CPU almost all the time
- * and have little contention except when we get to ENOSPC conditions.
- *
- * Basically, this lock becomes a barrier that enables us to lock out the fast
- * path while we do things like enabling and disabling counters and
- * synchronising the counters.
- *
- * Locking rules:
- *
- *     1. m_sb_lock before picking up per-cpu locks
- *     2. per-cpu locks always picked up via for_each_online_cpu() order
- *     3. accurate counter sync requires m_sb_lock + per cpu locks
- *     4. modifying per-cpu counters requires holding per-cpu lock
- *     5. modifying global counters requires holding m_sb_lock
- *     6. enabling or disabling a counter requires holding the m_sb_lock 
- *        and _none_ of the per-cpu locks.
- *
- * Disabled counters are only ever re-enabled by a balance operation
- * that results in more free resources per CPU than a given threshold.
- * To ensure counters don't remain disabled, they are rebalanced when
- * the global resource goes above a higher threshold (i.e. some hysteresis
- * is present to prevent thrashing).
- */
-
-#ifdef CONFIG_HOTPLUG_CPU
-/*
- * hot-plug CPU notifier support.
- *
- * We need a notifier per filesystem as we need to be able to identify
- * the filesystem to balance the counters out. This is achieved by
- * having a notifier block embedded in the xfs_mount_t and doing pointer
- * magic to get the mount pointer from the notifier block address.
- */
-STATIC int
-xfs_icsb_cpu_notify(
-       struct notifier_block *nfb,
-       unsigned long action,
-       void *hcpu)
-{
-       xfs_icsb_cnts_t *cntp;
-       xfs_mount_t     *mp;
-
-       mp = (xfs_mount_t *)container_of(nfb, xfs_mount_t, m_icsb_notifier);
-       cntp = (xfs_icsb_cnts_t *)
-                       per_cpu_ptr(mp->m_sb_cnts, (unsigned long)hcpu);
-       switch (action) {
-       case CPU_UP_PREPARE:
-       case CPU_UP_PREPARE_FROZEN:
-               /* Easy Case - initialize the area and locks, and
-                * then rebalance when online does everything else for us. */
-               memset(cntp, 0, sizeof(xfs_icsb_cnts_t));
-               break;
-       case CPU_ONLINE:
-       case CPU_ONLINE_FROZEN:
-               xfs_icsb_lock(mp);
-               xfs_icsb_balance_counter(mp, XFS_SBS_ICOUNT, 0);
-               xfs_icsb_balance_counter(mp, XFS_SBS_IFREE, 0);
-               xfs_icsb_balance_counter(mp, XFS_SBS_FDBLOCKS, 0);
-               xfs_icsb_unlock(mp);
-               break;
-       case CPU_DEAD:
-       case CPU_DEAD_FROZEN:
-               /* Disable all the counters, then fold the dead cpu's
-                * count into the total on the global superblock and
-                * re-enable the counters. */
-               xfs_icsb_lock(mp);
-               spin_lock(&mp->m_sb_lock);
-               xfs_icsb_disable_counter(mp, XFS_SBS_ICOUNT);
-               xfs_icsb_disable_counter(mp, XFS_SBS_IFREE);
-               xfs_icsb_disable_counter(mp, XFS_SBS_FDBLOCKS);
-
-               mp->m_sb.sb_icount += cntp->icsb_icount;
-               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_ICOUNT, 0);
-               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);
-               break;
-       }
-
-       return NOTIFY_OK;
-}
-#endif /* CONFIG_HOTPLUG_CPU */
-
-int
-xfs_icsb_init_counters(
-       xfs_mount_t     *mp)
-{
-       xfs_icsb_cnts_t *cntp;
-       int             i;
-
-       mp->m_sb_cnts = alloc_percpu(xfs_icsb_cnts_t);
-       if (mp->m_sb_cnts == NULL)
-               return -ENOMEM;
-
-#ifdef CONFIG_HOTPLUG_CPU
-       mp->m_icsb_notifier.notifier_call = xfs_icsb_cpu_notify;
-       mp->m_icsb_notifier.priority = 0;
-       register_hotcpu_notifier(&mp->m_icsb_notifier);
-#endif /* CONFIG_HOTPLUG_CPU */
-
-       for_each_online_cpu(i) {
-               cntp = (xfs_icsb_cnts_t *)per_cpu_ptr(mp->m_sb_cnts, i);
-               memset(cntp, 0, sizeof(xfs_icsb_cnts_t));
-       }
-
-       mutex_init(&mp->m_icsb_mutex);
-
-       /*
-        * start with all counters disabled so that the
-        * initial balance kicks us off correctly
-        */
-       mp->m_icsb_counters = -1;
-       return 0;
-}
-
-void
-xfs_icsb_reinit_counters(
-       xfs_mount_t     *mp)
-{
-       xfs_icsb_lock(mp);
-       /*
-        * start with all counters disabled so that the
-        * initial balance kicks us off correctly
-        */
-       mp->m_icsb_counters = -1;
-       xfs_icsb_balance_counter(mp, XFS_SBS_ICOUNT, 0);
-       xfs_icsb_balance_counter(mp, XFS_SBS_IFREE, 0);
-       xfs_icsb_balance_counter(mp, XFS_SBS_FDBLOCKS, 0);
-       xfs_icsb_unlock(mp);
-}
-
-void
-xfs_icsb_destroy_counters(
-       xfs_mount_t     *mp)
-{
-       if (mp->m_sb_cnts) {
-               unregister_hotcpu_notifier(&mp->m_icsb_notifier);
-               free_percpu(mp->m_sb_cnts);
-       }
-       mutex_destroy(&mp->m_icsb_mutex);
-}
-
-STATIC void
-xfs_icsb_lock_cntr(
-       xfs_icsb_cnts_t *icsbp)
-{
-       while (test_and_set_bit(XFS_ICSB_FLAG_LOCK, &icsbp->icsb_flags)) {
-               ndelay(1000);
-       }
-}
-
-STATIC void
-xfs_icsb_unlock_cntr(
-       xfs_icsb_cnts_t *icsbp)
-{
-       clear_bit(XFS_ICSB_FLAG_LOCK, &icsbp->icsb_flags);
-}
-
-
-STATIC void
-xfs_icsb_lock_all_counters(
-       xfs_mount_t     *mp)
-{
-       xfs_icsb_cnts_t *cntp;
-       int             i;
-
-       for_each_online_cpu(i) {
-               cntp = (xfs_icsb_cnts_t *)per_cpu_ptr(mp->m_sb_cnts, i);
-               xfs_icsb_lock_cntr(cntp);
-       }
-}
-
-STATIC void
-xfs_icsb_unlock_all_counters(
-       xfs_mount_t     *mp)
-{
-       xfs_icsb_cnts_t *cntp;
-       int             i;
-
-       for_each_online_cpu(i) {
-               cntp = (xfs_icsb_cnts_t *)per_cpu_ptr(mp->m_sb_cnts, i);
-               xfs_icsb_unlock_cntr(cntp);
-       }
-}
-
-STATIC void
-xfs_icsb_count(
-       xfs_mount_t     *mp,
-       xfs_icsb_cnts_t *cnt,
-       int             flags)
-{
-       xfs_icsb_cnts_t *cntp;
-       int             i;
-
-       memset(cnt, 0, sizeof(xfs_icsb_cnts_t));
-
-       if (!(flags & XFS_ICSB_LAZY_COUNT))
-               xfs_icsb_lock_all_counters(mp);
-
-       for_each_online_cpu(i) {
-               cntp = (xfs_icsb_cnts_t *)per_cpu_ptr(mp->m_sb_cnts, i);
-               cnt->icsb_icount += cntp->icsb_icount;
-               cnt->icsb_ifree += cntp->icsb_ifree;
-               cnt->icsb_fdblocks += cntp->icsb_fdblocks;
-       }
-
-       if (!(flags & XFS_ICSB_LAZY_COUNT))
-               xfs_icsb_unlock_all_counters(mp);
-}
-
-STATIC int
-xfs_icsb_counter_disabled(
-       xfs_mount_t     *mp,
-       xfs_sb_field_t  field)
-{
-       ASSERT((field >= XFS_SBS_ICOUNT) && (field <= XFS_SBS_FDBLOCKS));
-       return test_bit(field, &mp->m_icsb_counters);
-}
-
-STATIC void
-xfs_icsb_disable_counter(
-       xfs_mount_t     *mp,
-       xfs_sb_field_t  field)
-{
-       xfs_icsb_cnts_t cnt;
-
-       ASSERT((field >= XFS_SBS_ICOUNT) && (field <= XFS_SBS_FDBLOCKS));
-
-       /*
-        * If we are already disabled, then there is nothing to do
-        * here. We check before locking all the counters to avoid
-        * the expensive lock operation when being called in the
-        * slow path and the counter is already disabled. This is
-        * safe because the only time we set or clear this state is under
-        * the m_icsb_mutex.
-        */
-       if (xfs_icsb_counter_disabled(mp, field))
-               return;
-
-       xfs_icsb_lock_all_counters(mp);
-       if (!test_and_set_bit(field, &mp->m_icsb_counters)) {
-               /* drain back to superblock */
-
-               xfs_icsb_count(mp, &cnt, XFS_ICSB_LAZY_COUNT);
-               switch(field) {
-               case XFS_SBS_ICOUNT:
-                       mp->m_sb.sb_icount = cnt.icsb_icount;
-                       break;
-               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;
-               default:
-                       BUG();
-               }
-       }
-
-       xfs_icsb_unlock_all_counters(mp);
-}
-
-STATIC void
-xfs_icsb_enable_counter(
-       xfs_mount_t     *mp,
-       xfs_sb_field_t  field,
-       uint64_t        count,
-       uint64_t        resid)
-{
-       xfs_icsb_cnts_t *cntp;
-       int             i;
-
-       ASSERT((field >= XFS_SBS_ICOUNT) && (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_ICOUNT:
-                       cntp->icsb_icount = count + resid;
-                       break;
-               case XFS_SBS_IFREE:
-                       cntp->icsb_ifree = count + resid;
-                       break;
-               case XFS_SBS_FDBLOCKS:
-                       cntp->icsb_fdblocks = count + resid;
-                       break;
-               default:
-                       BUG();
-                       break;
-               }
-               resid = 0;
-       }
-       clear_bit(field, &mp->m_icsb_counters);
-       xfs_icsb_unlock_all_counters(mp);
-}
-
-void
-xfs_icsb_sync_counters_locked(
-       xfs_mount_t     *mp,
-       int             flags)
-{
-       xfs_icsb_cnts_t cnt;
-
-       xfs_icsb_count(mp, &cnt, flags);
-
-       if (!xfs_icsb_counter_disabled(mp, XFS_SBS_ICOUNT))
-               mp->m_sb.sb_icount = cnt.icsb_icount;
-       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;
-}
-
-/*
- * Accurate update of per-cpu counters to incore superblock
- */
-void
-xfs_icsb_sync_counters(
-       xfs_mount_t     *mp,
-       int             flags)
-{
-       spin_lock(&mp->m_sb_lock);
-       xfs_icsb_sync_counters_locked(mp, flags);
-       spin_unlock(&mp->m_sb_lock);
-}
-
-/*
- * Balance and enable/disable counters as necessary.
- *
- * Thresholds for re-enabling counters are somewhat magic.  inode counts are
- * chosen to be the same number as single on disk allocation chunk per CPU, and
- * free blocks is something far enough zero that we aren't going thrash when we
- * get near ENOSPC. We also need to supply a minimum we require per cpu to
- * prevent looping endlessly when xfs_alloc_space asks for more than will
- * be distributed to a single CPU but each CPU has enough blocks to be
- * reenabled.
- *
- * Note that we can be called when counters are already disabled.
- * xfs_icsb_disable_counter() optimises the counter locking in this case to
- * prevent locking every per-cpu counter needlessly.
- */
-
-#define XFS_ICSB_INO_CNTR_REENABLE     (uint64_t)64
-#define XFS_ICSB_FDBLK_CNTR_REENABLE(mp) \
-               (uint64_t)(512 + XFS_ALLOC_SET_ASIDE(mp))
-STATIC void
-xfs_icsb_balance_counter_locked(
-       xfs_mount_t     *mp,
-       xfs_sb_field_t  field,
-       int             min_per_cpu)
-{
-       uint64_t        count, resid;
-       int             weight = num_online_cpus();
-       uint64_t        min = (uint64_t)min_per_cpu;
-
-       /* disable counter and sync counter */
-       xfs_icsb_disable_counter(mp, field);
-
-       /* update counters  - first CPU gets residual*/
-       switch (field) {
-       case XFS_SBS_ICOUNT:
-               count = mp->m_sb.sb_icount;
-               resid = do_div(count, weight);
-               if (count < max(min, XFS_ICSB_INO_CNTR_REENABLE))
-                       return;
-               break;
-       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);
-               if (count < max(min, XFS_ICSB_FDBLK_CNTR_REENABLE(mp)))
-                       return;
-               break;
-       default:
-               BUG();
-               count = resid = 0;      /* quiet, gcc */
-               break;
-       }
-
-       xfs_icsb_enable_counter(mp, field, count, resid);
-}
-
-STATIC void
-xfs_icsb_balance_counter(
-       xfs_mount_t     *mp,
-       xfs_sb_field_t  fields,
-       int             min_per_cpu)
-{
-       spin_lock(&mp->m_sb_lock);
-       xfs_icsb_balance_counter_locked(mp, fields, min_per_cpu);
-       spin_unlock(&mp->m_sb_lock);
-}
-
-int
-xfs_icsb_modify_counters(
-       xfs_mount_t     *mp,
-       xfs_sb_field_t  field,
-       int64_t         delta,
-       int             rsvd)
-{
-       xfs_icsb_cnts_t *icsbp;
-       long long       lcounter;       /* long counter for 64 bit fields */
-       int             ret = 0;
-
-       might_sleep();
-again:
-       preempt_disable();
-       icsbp = this_cpu_ptr(mp->m_sb_cnts);
-
-       /*
-        * if the counter is disabled, go to slow path
-        */
-       if (unlikely(xfs_icsb_counter_disabled(mp, field)))
-               goto slow_path;
-       xfs_icsb_lock_cntr(icsbp);
-       if (unlikely(xfs_icsb_counter_disabled(mp, field))) {
-               xfs_icsb_unlock_cntr(icsbp);
-               goto slow_path;
-       }
-
-       switch (field) {
-       case XFS_SBS_ICOUNT:
-               lcounter = icsbp->icsb_icount;
-               lcounter += delta;
-               if (unlikely(lcounter < 0))
-                       goto balance_counter;
-               icsbp->icsb_icount = lcounter;
-               break;
-
-       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);
-
-               lcounter = icsbp->icsb_fdblocks - XFS_ALLOC_SET_ASIDE(mp);
-               lcounter += delta;
-               if (unlikely(lcounter < 0))
-                       goto balance_counter;
-               icsbp->icsb_fdblocks = lcounter + XFS_ALLOC_SET_ASIDE(mp);
-               break;
-       default:
-               BUG();
-               break;
-       }
-       xfs_icsb_unlock_cntr(icsbp);
-       preempt_enable();
-       return 0;
-
-slow_path:
-       preempt_enable();
-
-       /*
-        * serialise with a mutex so we don't burn lots of cpu on
-        * the superblock lock. We still need to hold the superblock
-        * lock, however, when we modify the global structures.
-        */
-       xfs_icsb_lock(mp);
-
-       /*
-        * Now running atomically.
-        *
-        * If the counter is enabled, someone has beaten us to rebalancing.
-        * Drop the lock and try again in the fast path....
-        */
-       if (!(xfs_icsb_counter_disabled(mp, field))) {
-               xfs_icsb_unlock(mp);
-               goto again;
-       }
-
-       /*
-        * The counter is currently disabled. Because we are
-        * running atomically here, we know a rebalance cannot
-        * be in progress. Hence we can go straight to operating
-        * on the global superblock. We do not call xfs_mod_incore_sb()
-        * here even though we need to get the m_sb_lock. Doing so
-        * will cause us to re-enter this function and deadlock.
-        * Hence we get the m_sb_lock ourselves and then call
-        * xfs_mod_incore_sb_unlocked() as the unlocked path operates
-        * directly on the global counters.
-        */
-       spin_lock(&mp->m_sb_lock);
-       ret = xfs_mod_incore_sb_unlocked(mp, field, delta, rsvd);
-       spin_unlock(&mp->m_sb_lock);
-
-       /*
-        * Now that we've modified the global superblock, we
-        * may be able to re-enable the distributed counters
-        * (e.g. lots of space just got freed). After that
-        * we are done.
-        */
-       if (ret != ENOSPC)
-               xfs_icsb_balance_counter(mp, field, 0);
-       xfs_icsb_unlock(mp);
-       return ret;
-
-balance_counter:
-       xfs_icsb_unlock_cntr(icsbp);
-       preempt_enable();
-
-       /*
-        * We may have multiple threads here if multiple per-cpu
-        * counters run dry at the same time. This will mean we can
-        * do more balances than strictly necessary but it is not
-        * the common slowpath case.
-        */
-       xfs_icsb_lock(mp);
-
-       /*
-        * running atomically.
-        *
-        * This will leave the counter in the correct state for future
-        * accesses. After the rebalance, we simply try again and our retry
-        * will either succeed through the fast path or slow path without
-        * another balance operation being required.
-        */
-       xfs_icsb_balance_counter(mp, field, delta);
-       xfs_icsb_unlock(mp);
-       goto again;
-}
-
-#endif
diff --git a/fs/xfs/xfs_mount.h b/fs/xfs/xfs_mount.h
index 5861b49..42d31df 100644
--- a/fs/xfs/xfs_mount.h
+++ b/fs/xfs/xfs_mount.h
@@ -65,44 +65,19 @@ struct xfs_nameops;
 struct xfs_ail;
 struct xfs_quotainfo;
 
-#ifdef HAVE_PERCPU_SB
-
 /*
- * Valid per-cpu incore superblock counters. Note that if you add new counters,
- * you may need to define new counter disabled bit field descriptors as there
- * are more possible fields in the superblock that can fit in a bitfield on a
- * 32 bit platform. The XFS_SBS_* values for the current current counters just
- * fit.
+ * Per-cpu incore superblock counters.
  */
-typedef struct xfs_icsb_cnts {
-       uint64_t        icsb_fdblocks;
-       uint64_t        icsb_ifree;
-       uint64_t        icsb_icount;
-       unsigned long   icsb_flags;
-} xfs_icsb_cnts_t;
-
-#define XFS_ICSB_FLAG_LOCK     (1 << 0)        /* counter lock bit */
-
-#define XFS_ICSB_LAZY_COUNT    (1 << 1)        /* accuracy not needed */
+enum {
+       XFS_ICSB_FDBLOCKS = 0,
+       XFS_ICSB_IFREE,
+       XFS_ICSB_ICOUNT,
+       XFS_ICSB_MAX,
+};
 
-extern int     xfs_icsb_init_counters(struct xfs_mount *);
-extern void    xfs_icsb_reinit_counters(struct xfs_mount *);
-extern void    xfs_icsb_destroy_counters(struct xfs_mount *);
-extern void    xfs_icsb_sync_counters(struct xfs_mount *, int);
-extern void    xfs_icsb_sync_counters_locked(struct xfs_mount *, int);
 extern int     xfs_icsb_modify_counters(struct xfs_mount *, xfs_sb_field_t,
                                                int64_t, int);
 
-#else
-#define xfs_icsb_init_counters(mp)             (0)
-#define xfs_icsb_destroy_counters(mp)          do { } while (0)
-#define xfs_icsb_reinit_counters(mp)           do { } while (0)
-#define xfs_icsb_sync_counters(mp, flags)      do { } while (0)
-#define xfs_icsb_sync_counters_locked(mp, flags) do { } while (0)
-#define xfs_icsb_modify_counters(mp, field, delta, rsvd) \
-       xfs_mod_incore_sb(mp, field, delta, rsvd)
-#endif
-
 typedef struct xfs_mount {
        struct super_block      *m_super;
        xfs_tid_t               m_tid;          /* next unused tid for fs */
@@ -186,12 +161,6 @@ typedef struct xfs_mount {
        struct xfs_chash        *m_chash;       /* fs private inode per-cluster
                                                 * hash table */
        atomic_t                m_active_trans; /* number trans frozen */
-#ifdef HAVE_PERCPU_SB
-       xfs_icsb_cnts_t __percpu *m_sb_cnts;    /* per-cpu superblock counters 
*/
-       unsigned long           m_icsb_counters; /* disabled per-cpu counters */
-       struct notifier_block   m_icsb_notifier; /* hotplug cpu notifier */
-       struct mutex            m_icsb_mutex;   /* balancer sync lock */
-#endif
        struct xfs_mru_cache    *m_filestream;  /* per-mount filestream data */
        struct task_struct      *m_sync_task;   /* generalised sync thread */
        xfs_sync_work_t         m_sync_work;    /* work item for VFS_SYNC */
@@ -202,6 +171,7 @@ typedef struct xfs_mount {
        __int64_t               m_update_flags; /* sb flags we need to update
                                                   on the next remount,rw */
        struct shrinker         m_inode_shrink; /* inode reclaim shrinker */
+       struct percpu_counter   m_icsb[XFS_ICSB_MAX];
 } xfs_mount_t;
 
 /*
@@ -333,26 +303,6 @@ struct xfs_perag *xfs_perag_get_tag(struct xfs_mount *mp, 
xfs_agnumber_t agno,
 void   xfs_perag_put(struct xfs_perag *pag);
 
 /*
- * Per-cpu superblock locking functions
- */
-#ifdef HAVE_PERCPU_SB
-static inline void
-xfs_icsb_lock(xfs_mount_t *mp)
-{
-       mutex_lock(&mp->m_icsb_mutex);
-}
-
-static inline void
-xfs_icsb_unlock(xfs_mount_t *mp)
-{
-       mutex_unlock(&mp->m_icsb_mutex);
-}
-#else
-#define xfs_icsb_lock(mp)
-#define xfs_icsb_unlock(mp)
-#endif
-
-/*
  * This structure is for use by the xfs_mod_incore_sb_batch() routine.
  * xfs_growfs can specify a few fields which are more than int limit
  */
@@ -379,6 +329,11 @@ extern int xfs_sb_validate_fsb_count(struct xfs_sb *, 
__uint64_t);
 
 extern int     xfs_dev_is_read_only(struct xfs_mount *, char *);
 
+extern int     xfs_icsb_init_counters(struct xfs_mount *);
+extern void    xfs_icsb_reinit_counters(struct xfs_mount *);
+extern void    xfs_icsb_destroy_counters(struct xfs_mount *);
+extern void    xfs_icsb_sync_counters(struct xfs_mount *);
+
 #endif /* __KERNEL__ */
 
 extern void    xfs_mod_sb(struct xfs_trans *, __int64_t);
-- 
1.7.2.3

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