diff --git a/fs/xfs/xfs_mount.c b/fs/xfs/xfs_mount.c index 397730f570b9..37c612ce3d05 100644 --- a/fs/xfs/xfs_mount.c +++ b/fs/xfs/xfs_mount.c @@ -52,21 +52,19 @@ STATIC void xfs_unmountfs_wait(xfs_mount_t *); #ifdef HAVE_PERCPU_SB STATIC void xfs_icsb_destroy_counters(xfs_mount_t *); -STATIC void xfs_icsb_balance_counter(xfs_mount_t *, xfs_sb_field_t, int); +STATIC void xfs_icsb_balance_counter(xfs_mount_t *, xfs_sb_field_t, int, +int); STATIC void xfs_icsb_sync_counters(xfs_mount_t *); STATIC int xfs_icsb_modify_counters(xfs_mount_t *, xfs_sb_field_t, int, int); -STATIC int xfs_icsb_modify_counters_locked(xfs_mount_t *, xfs_sb_field_t, - int, int); STATIC int xfs_icsb_disable_counter(xfs_mount_t *, xfs_sb_field_t); #else #define xfs_icsb_destroy_counters(mp) do { } while (0) -#define xfs_icsb_balance_counter(mp, a, b) do { } while (0) +#define xfs_icsb_balance_counter(mp, a, b, c) do { } while (0) #define xfs_icsb_sync_counters(mp) do { } while (0) #define xfs_icsb_modify_counters(mp, a, b, c) do { } while (0) -#define xfs_icsb_modify_counters_locked(mp, a, b, c) do { } while (0) #endif @@ -545,9 +543,11 @@ xfs_readsb(xfs_mount_t *mp, int flags) ASSERT(XFS_BUF_VALUSEMA(bp) <= 0); } - 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); + mutex_lock(&mp->m_icsb_mutex); + xfs_icsb_balance_counter(mp, XFS_SBS_ICOUNT, 0, 0); + xfs_icsb_balance_counter(mp, XFS_SBS_IFREE, 0, 0); + xfs_icsb_balance_counter(mp, XFS_SBS_FDBLOCKS, 0, 0); + mutex_unlock(&mp->m_icsb_mutex); mp->m_sb_bp = bp; xfs_buf_relse(bp); @@ -1485,9 +1485,11 @@ xfs_mod_incore_sb_batch(xfs_mount_t *mp, xfs_mod_sb_t *msb, uint nmsb, int rsvd) case XFS_SBS_IFREE: case XFS_SBS_FDBLOCKS: if (!(mp->m_flags & XFS_MOUNT_NO_PERCPU_SB)) { - status = xfs_icsb_modify_counters_locked(mp, + XFS_SB_UNLOCK(mp, s); + status = xfs_icsb_modify_counters(mp, msbp->msb_field, msbp->msb_delta, rsvd); + s = XFS_SB_LOCK(mp); break; } /* FALLTHROUGH */ @@ -1521,11 +1523,12 @@ xfs_mod_incore_sb_batch(xfs_mount_t *mp, xfs_mod_sb_t *msb, uint nmsb, int rsvd) case XFS_SBS_IFREE: case XFS_SBS_FDBLOCKS: if (!(mp->m_flags & XFS_MOUNT_NO_PERCPU_SB)) { - status = - xfs_icsb_modify_counters_locked(mp, + XFS_SB_UNLOCK(mp, s); + status = xfs_icsb_modify_counters(mp, msbp->msb_field, -(msbp->msb_delta), rsvd); + s = XFS_SB_LOCK(mp); break; } /* FALLTHROUGH */ @@ -1733,14 +1736,17 @@ xfs_icsb_cpu_notify( 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); + mutex_lock(&mp->m_icsb_mutex); + xfs_icsb_balance_counter(mp, XFS_SBS_ICOUNT, 0, 0); + xfs_icsb_balance_counter(mp, XFS_SBS_IFREE, 0, 0); + xfs_icsb_balance_counter(mp, XFS_SBS_FDBLOCKS, 0, 0); + mutex_unlock(&mp->m_icsb_mutex); 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. */ + mutex_lock(&mp->m_icsb_mutex); s = XFS_SB_LOCK(mp); xfs_icsb_disable_counter(mp, XFS_SBS_ICOUNT); xfs_icsb_disable_counter(mp, XFS_SBS_IFREE); @@ -1752,10 +1758,14 @@ xfs_icsb_cpu_notify( 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_icsb_balance_counter(mp, XFS_SBS_ICOUNT, + XFS_ICSB_SB_LOCKED, 0); + xfs_icsb_balance_counter(mp, XFS_SBS_IFREE, + XFS_ICSB_SB_LOCKED, 0); + xfs_icsb_balance_counter(mp, XFS_SBS_FDBLOCKS, + XFS_ICSB_SB_LOCKED, 0); XFS_SB_UNLOCK(mp, s); + mutex_unlock(&mp->m_icsb_mutex); break; } @@ -1784,6 +1794,9 @@ xfs_icsb_init_counters( 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 @@ -1888,6 +1901,17 @@ xfs_icsb_disable_counter( 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 0; + xfs_icsb_lock_all_counters(mp); if (!test_and_set_bit(field, &mp->m_icsb_counters)) { /* drain back to superblock */ @@ -1997,24 +2021,33 @@ xfs_icsb_sync_counters_lazy( /* * 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. + * 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 64 + +#define XFS_ICSB_INO_CNTR_REENABLE (uint64_t)64 #define XFS_ICSB_FDBLK_CNTR_REENABLE(mp) \ - (512 + XFS_ALLOC_SET_ASIDE(mp)) + (uint64_t)(512 + XFS_ALLOC_SET_ASIDE(mp)) STATIC void xfs_icsb_balance_counter( xfs_mount_t *mp, xfs_sb_field_t field, - int flags) + int flags, + int min_per_cpu) { uint64_t count, resid; int weight = num_online_cpus(); int s; + uint64_t min = (uint64_t)min_per_cpu; if (!(flags & XFS_ICSB_SB_LOCKED)) s = XFS_SB_LOCK(mp); @@ -2027,19 +2060,19 @@ xfs_icsb_balance_counter( case XFS_SBS_ICOUNT: count = mp->m_sb.sb_icount; resid = do_div(count, weight); - if (count < XFS_ICSB_INO_CNTR_REENABLE) + if (count < max(min, 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) + if (count < max(min, 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)) + if (count < max(min, XFS_ICSB_FDBLK_CNTR_REENABLE(mp))) goto out; break; default: @@ -2054,32 +2087,39 @@ out: XFS_SB_UNLOCK(mp, s); } -STATIC int -xfs_icsb_modify_counters_int( +int +xfs_icsb_modify_counters( xfs_mount_t *mp, xfs_sb_field_t field, int delta, - int rsvd, - int flags) + int rsvd) { 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; + int cpu, ret = 0, s; + might_sleep(); again: cpu = get_cpu(); - icsbp = (xfs_icsb_cnts_t *)per_cpu_ptr(mp->m_sb_cnts, cpu), - xfs_icsb_lock_cntr(icsbp); + icsbp = (xfs_icsb_cnts_t *)per_cpu_ptr(mp->m_sb_cnts, cpu); + + /* + * 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 slow_path; + goto balance_counter; icsbp->icsb_icount = lcounter; break; @@ -2087,7 +2127,7 @@ again: lcounter = icsbp->icsb_ifree; lcounter += delta; if (unlikely(lcounter < 0)) - goto slow_path; + goto balance_counter; icsbp->icsb_ifree = lcounter; break; @@ -2097,7 +2137,7 @@ again: lcounter = icsbp->icsb_fdblocks - XFS_ALLOC_SET_ASIDE(mp); lcounter += delta; if (unlikely(lcounter < 0)) - goto slow_path; + goto balance_counter; icsbp->icsb_fdblocks = lcounter + XFS_ALLOC_SET_ASIDE(mp); break; default: @@ -2106,72 +2146,78 @@ again: } 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: + put_cpu(); + + /* + * 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. + */ + mutex_lock(&mp->m_icsb_mutex); + + /* + * 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))) { + mutex_unlock(&mp->m_icsb_mutex); + 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 SB_LOCK. Doing so + * will cause us to re-enter this function and deadlock. + * Hence we get the SB_LOCK ourselves and then call + * xfs_mod_incore_sb_unlocked() as the unlocked path operates + * directly on the global counters. + */ + s = XFS_SB_LOCK(mp); + ret = xfs_mod_incore_sb_unlocked(mp, field, delta, rsvd); + XFS_SB_UNLOCK(mp, s); + + /* + * 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, 0); + mutex_unlock(&mp->m_icsb_mutex); + return ret; + +balance_counter: 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); - } + /* + * 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. + */ + mutex_lock(&mp->m_icsb_mutex); - ret = xfs_mod_incore_sb_unlocked(mp, field, delta, rsvd); - - if (locked) - XFS_SB_UNLOCK(mp, s); - return ret; + /* + * 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, 0, delta); + mutex_unlock(&mp->m_icsb_mutex); + goto again; } -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 diff --git a/fs/xfs/xfs_mount.h b/fs/xfs/xfs_mount.h index e5f396ff9a3d..a2295df61d2e 100644 --- a/fs/xfs/xfs_mount.h +++ b/fs/xfs/xfs_mount.h @@ -419,6 +419,7 @@ typedef struct xfs_mount { xfs_icsb_cnts_t *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 } xfs_mount_t;