xfs: Remove icsb infrastructure

Now that the in-core superblock infrastructure has been replaced with
generic per-cpu counters, we don't need it anymore. Nuke it from
orbit so we are sure that it won't haunt us again...

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

1 files changed, 1 insertions, 515 deletions

diff --git a/fs/xfs/xfs_mount.c b/fs/xfs/xfs_mount.c
index 767c09a5d3ff..05b392e35e35 100644
--- a/fs/xfs/xfs_mount.c
+++ b/fs/xfs/xfs_mount.c
@@ -43,18 +43,6 @@
 #include "xfs_sysfs.h"
 
 
-#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 DEFINE_MUTEX(xfs_uuid_table_mutex);
 static int xfs_uuid_table_size;
 static uuid_t *xfs_uuid_table;
@@ -347,8 +335,7 @@ reread:
                 goto reread;
         }
 
-        /* Initialize per-cpu counters */
-        xfs_icsb_reinit_counters(mp);
+        xfs_reinit_percpu_counters(mp);
 
         /* no need to be quiet anymore, so reset the buf ops */
         bp->b_ops = &xfs_sb_buf_ops;
@@ -1087,8 +1074,6 @@ xfs_log_sbcount(xfs_mount_t *mp)
         if (!xfs_fs_writable(mp, SB_FREEZE_COMPLETE))
                 return 0;
 
-        xfs_icsb_sync_counters(mp, 0);
-
         /*
          * we don't need to do this if we are updating the superblock
          * counters on every modification.
@@ -1466,502 +1451,3 @@ 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_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);
-
-                memset(cntp, 0, sizeof(xfs_icsb_cnts_t));
-
-                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             error;
-        int             i;
-
-        error = percpu_counter_init(&mp->m_icount, 0, GFP_KERNEL);
-        if (error)
-                return error;
-
-        error = percpu_counter_init(&mp->m_ifree, 0, GFP_KERNEL);
-        if (error)
-                goto free_icount;
-
-        error = percpu_counter_init(&mp->m_fdblocks, 0, GFP_KERNEL);
-        if (error)
-                goto free_ifree;
-
-        mp->m_sb_cnts = alloc_percpu(xfs_icsb_cnts_t);
-        if (!mp->m_sb_cnts) {
-                error = -ENOMEM;
-                goto free_fdblocks;
-        }
-
-        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;
-
-#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 */
-
-        return 0;
-
-free_fdblocks:
-        percpu_counter_destroy(&mp->m_fdblocks);
-free_ifree:
-        percpu_counter_destroy(&mp->m_ifree);
-free_icount:
-        percpu_counter_destroy(&mp->m_icount);
-        return error;
-}
-
-void
-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);
-        percpu_counter_set(&mp->m_fdblocks, mp->m_sb.sb_fdblocks);
-
-        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_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);
-        }
-
-        percpu_counter_destroy(&mp->m_icount);
-        percpu_counter_destroy(&mp->m_ifree);
-        percpu_counter_destroy(&mp->m_fdblocks);
-
-        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)
-{
-        memset(cnt, 0, sizeof(xfs_icsb_cnts_t));
-
-        if (!(flags & XFS_ICSB_LAZY_COUNT))
-                xfs_icsb_lock_all_counters(mp);
-
-
-        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)
-{
-        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;
-
-        /*
-         * 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) {
-                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)
-{
-        int             i;
-
-        xfs_icsb_lock_all_counters(mp);
-        for_each_online_cpu(i) {
-                switch (field) {
-                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);
-}
-
-/*
- * 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;
-
-        /* disable counter and sync counter */
-        xfs_icsb_disable_counter(mp, field);
-
-        /* update counters  - first CPU gets residual*/
-        switch (field) {
-        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;
-        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) {
-        default:
-                BUG();
-                goto balance_counter; /* be still, gcc */
-        }
-        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