-
-
-#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 it's 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. XFS_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 XFS_SB_LOCK + per cpu locks
- * 4. modifying per-cpu counters requires holding per-cpu lock
- * 5. modifying global counters requires holding XFS_SB_LOCK
- * 6. enabling or disabling a counter requires holding the XFS_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;
- int s;
-
- 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:
- /* 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:
- 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);
- break;
- case CPU_DEAD:
- /* Disable all the counters, then fold the dead cpu's
- * count into the total on the global superblock and
- * re-enable the counters. */
- s = XFS_SB_LOCK(mp);
- 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(mp, XFS_SBS_ICOUNT, XFS_ICSB_SB_LOCKED);
- xfs_icsb_balance_counter(mp, XFS_SBS_IFREE, XFS_ICSB_SB_LOCKED);
- xfs_icsb_balance_counter(mp, XFS_SBS_FDBLOCKS, XFS_ICSB_SB_LOCKED);
- XFS_SB_UNLOCK(mp, s);
- 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));
- }
- /*
- * start with all counters disabled so that the
- * initial balance kicks us off correctly
- */
- mp->m_icsb_counters = -1;
- return 0;
-}
-
-STATIC 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);
- }
-}
-
-STATIC inline 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 inline void
-xfs_icsb_unlock_cntr(
- xfs_icsb_cnts_t *icsbp)
-{
- clear_bit(XFS_ICSB_FLAG_LOCK, &icsbp->icsb_flags);
-}
-
-
-STATIC inline 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 inline 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 int
-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));
-
- 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_SB_LOCKED|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);
-
- return 0;
-}
-
-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);
-}
-
-STATIC void
-xfs_icsb_sync_counters_int(
- xfs_mount_t *mp,
- int flags)
-{
- xfs_icsb_cnts_t cnt;
- int s;
-
- /* Pass 1: lock all counters */
- if ((flags & XFS_ICSB_SB_LOCKED) == 0)
- s = XFS_SB_LOCK(mp);
-
- xfs_icsb_count(mp, &cnt, flags);
-
- /* Step 3: update mp->m_sb fields */
- 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;
-
- if ((flags & XFS_ICSB_SB_LOCKED) == 0)
- XFS_SB_UNLOCK(mp, s);
-}
-
-/*
- * Accurate update of per-cpu counters to incore superblock
- */
-STATIC void
-xfs_icsb_sync_counters(
- xfs_mount_t *mp)
-{
- xfs_icsb_sync_counters_int(mp, 0);
-}
-
-/*
- * lazy addition used for things like df, background sb syncs, etc
- */
-void
-xfs_icsb_sync_counters_lazy(
- xfs_mount_t *mp)
-{
- xfs_icsb_sync_counters_int(mp, XFS_ICSB_LAZY_COUNT);
-}
-
-/*
- * 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.
- */
-#define XFS_ICSB_INO_CNTR_REENABLE 64
-#define XFS_ICSB_FDBLK_CNTR_REENABLE(mp) \
- (512 + XFS_ALLOC_SET_ASIDE(mp))
-STATIC void
-xfs_icsb_balance_counter(
- xfs_mount_t *mp,
- xfs_sb_field_t field,
- int flags)
-{
- uint64_t count, resid;
- int weight = num_online_cpus();
- int s;
-
- if (!(flags & XFS_ICSB_SB_LOCKED))
- s = XFS_SB_LOCK(mp);
-
- /* 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 < XFS_ICSB_INO_CNTR_REENABLE)
- goto out;
- break;
- case XFS_SBS_IFREE:
- count = mp->m_sb.sb_ifree;
- resid = do_div(count, weight);
- if (count < XFS_ICSB_INO_CNTR_REENABLE)
- goto out;
- break;
- case XFS_SBS_FDBLOCKS:
- count = mp->m_sb.sb_fdblocks;
- resid = do_div(count, weight);
- if (count < XFS_ICSB_FDBLK_CNTR_REENABLE(mp))
- goto out;
- break;
- default:
- BUG();
- count = resid = 0; /* quiet, gcc */
- break;
- }
-
- xfs_icsb_enable_counter(mp, field, count, resid);
-out:
- if (!(flags & XFS_ICSB_SB_LOCKED))
- XFS_SB_UNLOCK(mp, s);
-}
-
-STATIC int
-xfs_icsb_modify_counters_int(
- xfs_mount_t *mp,
- xfs_sb_field_t field,
- int delta,
- int rsvd,
- int flags)
-{
- xfs_icsb_cnts_t *icsbp;
- long long lcounter; /* long counter for 64 bit fields */
- int cpu, s, locked = 0;
- int ret = 0, balance_done = 0;
-
-again:
- cpu = get_cpu();
- icsbp = (xfs_icsb_cnts_t *)per_cpu_ptr(mp->m_sb_cnts, cpu),
- xfs_icsb_lock_cntr(icsbp);
- if (unlikely(xfs_icsb_counter_disabled(mp, field)))
- goto slow_path;
-
- switch (field) {
- case XFS_SBS_ICOUNT:
- lcounter = icsbp->icsb_icount;
- lcounter += delta;
- if (unlikely(lcounter < 0))
- goto slow_path;
- icsbp->icsb_icount = lcounter;
- break;
-
- case XFS_SBS_IFREE:
- lcounter = icsbp->icsb_ifree;
- lcounter += delta;
- if (unlikely(lcounter < 0))
- goto slow_path;
- 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 slow_path;
- icsbp->icsb_fdblocks = lcounter + XFS_ALLOC_SET_ASIDE(mp);
- break;
- default:
- BUG();
- break;
- }
- xfs_icsb_unlock_cntr(icsbp);
- put_cpu();
- if (locked)
- XFS_SB_UNLOCK(mp, s);
- return 0;
-
- /*
- * The slow path needs to be run with the SBLOCK
- * held so that we prevent other threads from
- * attempting to run this path at the same time.
- * this provides exclusion for the balancing code,
- * and exclusive fallback if the balance does not
- * provide enough resources to continue in an unlocked
- * manner.
- */
-slow_path:
- xfs_icsb_unlock_cntr(icsbp);
- put_cpu();
-
- /* need to hold superblock incase we need
- * to disable a counter */
- if (!(flags & XFS_ICSB_SB_LOCKED)) {
- s = XFS_SB_LOCK(mp);
- locked = 1;
- flags |= XFS_ICSB_SB_LOCKED;
- }
- if (!balance_done) {
- xfs_icsb_balance_counter(mp, field, flags);
- balance_done = 1;
- goto again;
- } else {
- /*
- * we might not have enough on this local
- * cpu to allocate for a bulk request.
- * We need to drain this field from all CPUs
- * and disable the counter fastpath
- */
- xfs_icsb_disable_counter(mp, field);
- }
-
- ret = xfs_mod_incore_sb_unlocked(mp, field, delta, rsvd);
-
- if (locked)
- XFS_SB_UNLOCK(mp, s);
- return ret;
-}
-
-STATIC int
-xfs_icsb_modify_counters(
- xfs_mount_t *mp,
- xfs_sb_field_t field,
- int delta,
- int rsvd)
-{
- return xfs_icsb_modify_counters_int(mp, field, delta, rsvd, 0);
-}
-
-/*
- * Called when superblock is already locked
- */
-STATIC int
-xfs_icsb_modify_counters_locked(
- xfs_mount_t *mp,
- xfs_sb_field_t field,
- int delta,
- int rsvd)
-{
- return xfs_icsb_modify_counters_int(mp, field, delta,
- rsvd, XFS_ICSB_SB_LOCKED);
-}
-#endif