xfs: use generic percpu counters for free block counter
XFS has hand-rolled per-cpu counters for the superblock since before
there was any generic implementation. The free block counter is
special in that it is used for ENOSPC detection outside transaction
contexts for for delayed allocation. This means that the counter
needs to be accurate at zero. The current per-cpu counter code jumps
through lots of hoops to ensure we never run past zero, but we don't
need to make all those jumps with the generic counter
implementation.
The generic counter implementation allows us to pass a "batch"
threshold at which the addition/subtraction to the counter value
will be folded back into global value under lock. We can use this
feature to reduce the batch size as we approach 0 in a very similar
manner to the existing counters and their rebalance algorithm. If we
use a batch size of 1 as we approach 0, then every addition and
subtraction will be done against the global value and hence allow
accurate detection of zero threshold crossing.
Hence we can replace the handrolled, accurate-at-zero counters with
generic percpu counters.
Note: this removes just enough of the icsb infrastructure to compile
without warnings. The rest will go in subsequent commits.
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
diff --git a/fs/xfs/xfs_mount.c b/fs/xfs/xfs_mount.c
index 650e8f1..767c09a 100644
--- a/fs/xfs/xfs_mount.c
+++ b/fs/xfs/xfs_mount.c
@@ -1114,7 +1114,6 @@
return 0;
}
-
int
xfs_mod_ifree(
struct xfs_mount *mp,
@@ -1128,6 +1127,92 @@
}
return 0;
}
+
+int
+xfs_mod_fdblocks(
+ struct xfs_mount *mp,
+ int64_t delta,
+ bool rsvd)
+{
+ int64_t lcounter;
+ long long res_used;
+ s32 batch;
+
+ if (delta > 0) {
+ /*
+ * If the reserve pool is depleted, put blocks back into it
+ * first. Most of the time the pool is full.
+ */
+ if (likely(mp->m_resblks == mp->m_resblks_avail)) {
+ percpu_counter_add(&mp->m_fdblocks, delta);
+ return 0;
+ }
+
+ spin_lock(&mp->m_sb_lock);
+ res_used = (long long)(mp->m_resblks - mp->m_resblks_avail);
+
+ if (res_used > delta) {
+ mp->m_resblks_avail += delta;
+ } else {
+ delta -= res_used;
+ mp->m_resblks_avail = mp->m_resblks;
+ percpu_counter_add(&mp->m_fdblocks, delta);
+ }
+ spin_unlock(&mp->m_sb_lock);
+ return 0;
+ }
+
+ /*
+ * Taking blocks away, need to be more accurate the closer we
+ * are to zero.
+ *
+ * batch size is set to a maximum of 1024 blocks - if we are
+ * allocating of freeing extents larger than this then we aren't
+ * going to be hammering the counter lock so a lock per update
+ * is not a problem.
+ *
+ * If the counter has a value of less than 2 * max batch size,
+ * then make everything serialise as we are real close to
+ * ENOSPC.
+ */
+#define __BATCH 1024
+ if (percpu_counter_compare(&mp->m_fdblocks, 2 * __BATCH) < 0)
+ batch = 1;
+ else
+ batch = __BATCH;
+#undef __BATCH
+
+ __percpu_counter_add(&mp->m_fdblocks, delta, batch);
+ if (percpu_counter_compare(&mp->m_fdblocks,
+ XFS_ALLOC_SET_ASIDE(mp)) >= 0) {
+ /* we had space! */
+ return 0;
+ }
+
+ /*
+ * lock up the sb for dipping into reserves before releasing the space
+ * that took us to ENOSPC.
+ */
+ spin_lock(&mp->m_sb_lock);
+ percpu_counter_add(&mp->m_fdblocks, -delta);
+ if (!rsvd)
+ goto fdblocks_enospc;
+
+ lcounter = (long long)mp->m_resblks_avail + delta;
+ if (lcounter >= 0) {
+ mp->m_resblks_avail = lcounter;
+ spin_unlock(&mp->m_sb_lock);
+ return 0;
+ }
+ printk_once(KERN_WARNING
+ "Filesystem \"%s\": reserve blocks depleted! "
+ "Consider increasing reserve pool size.",
+ mp->m_fsname);
+fdblocks_enospc:
+ spin_unlock(&mp->m_sb_lock);
+ return -ENOSPC;
+}
+
/*
* 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
@@ -1146,7 +1231,6 @@
{
int scounter; /* short counter for 32 bit fields */
long long lcounter; /* long counter for 64 bit fields */
- long long res_used, rem;
/*
* With the in-core superblock spin lock held, switch
@@ -1157,50 +1241,9 @@
switch (field) {
case XFS_SBS_ICOUNT:
case XFS_SBS_IFREE:
+ case XFS_SBS_FDBLOCKS:
ASSERT(0);
return -EINVAL;
- 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 -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 -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;
@@ -1323,7 +1366,7 @@
*
* Note that this function may not be used for the superblock values that
* are tracked with the in-memory per-cpu counters - a direct call to
- * xfs_icsb_modify_counters is required for these.
+ * xfs_mod_incore_sb is required for these.
*/
int
xfs_mod_incore_sb_batch(
@@ -1508,7 +1551,6 @@
case CPU_ONLINE:
case CPU_ONLINE_FROZEN:
xfs_icsb_lock(mp);
- xfs_icsb_balance_counter(mp, XFS_SBS_FDBLOCKS, 0);
xfs_icsb_unlock(mp);
break;
case CPU_DEAD:
@@ -1518,13 +1560,9 @@
* re-enable the counters. */
xfs_icsb_lock(mp);
spin_lock(&mp->m_sb_lock);
- xfs_icsb_disable_counter(mp, XFS_SBS_FDBLOCKS);
-
- mp->m_sb.sb_fdblocks += cntp->icsb_fdblocks;
memset(cntp, 0, sizeof(xfs_icsb_cnts_t));
- xfs_icsb_balance_counter_locked(mp, XFS_SBS_FDBLOCKS, 0);
spin_unlock(&mp->m_sb_lock);
xfs_icsb_unlock(mp);
break;
@@ -1550,10 +1588,14 @@
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_ifree;
+ goto free_fdblocks;
}
for_each_online_cpu(i) {
@@ -1577,6 +1619,8 @@
return 0;
+free_fdblocks:
+ percpu_counter_destroy(&mp->m_fdblocks);
free_ifree:
percpu_counter_destroy(&mp->m_ifree);
free_icount:
@@ -1590,6 +1634,7 @@
{
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);
/*
@@ -1597,7 +1642,6 @@
* initial balance kicks us off correctly
*/
mp->m_icsb_counters = -1;
- xfs_icsb_balance_counter(mp, XFS_SBS_FDBLOCKS, 0);
xfs_icsb_unlock(mp);
}
@@ -1612,6 +1656,7 @@
percpu_counter_destroy(&mp->m_icount);
percpu_counter_destroy(&mp->m_ifree);
+ percpu_counter_destroy(&mp->m_fdblocks);
mutex_destroy(&mp->m_icsb_mutex);
}
@@ -1665,18 +1710,11 @@
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_fdblocks += cntp->icsb_fdblocks;
- }
if (!(flags & XFS_ICSB_LAZY_COUNT))
xfs_icsb_unlock_all_counters(mp);
@@ -1687,7 +1725,6 @@
xfs_mount_t *mp,
xfs_sb_field_t field)
{
- ASSERT(field == XFS_SBS_FDBLOCKS);
return test_bit(field, &mp->m_icsb_counters);
}
@@ -1698,8 +1735,6 @@
{
xfs_icsb_cnts_t cnt;
- ASSERT(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
@@ -1717,9 +1752,6 @@
xfs_icsb_count(mp, &cnt, XFS_ICSB_LAZY_COUNT);
switch(field) {
- case XFS_SBS_FDBLOCKS:
- mp->m_sb.sb_fdblocks = cnt.icsb_fdblocks;
- break;
default:
BUG();
}
@@ -1735,18 +1767,11 @@
uint64_t count,
uint64_t resid)
{
- xfs_icsb_cnts_t *cntp;
int i;
- 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_FDBLOCKS:
- cntp->icsb_fdblocks = count + resid;
- break;
default:
BUG();
break;
@@ -1765,9 +1790,6 @@
xfs_icsb_cnts_t cnt;
xfs_icsb_count(mp, &cnt, flags);
-
- if (!xfs_icsb_counter_disabled(mp, XFS_SBS_FDBLOCKS))
- mp->m_sb.sb_fdblocks = cnt.icsb_fdblocks;
}
/*
@@ -1809,20 +1831,12 @@
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_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 */
@@ -1851,7 +1865,6 @@
int rsvd)
{
xfs_icsb_cnts_t *icsbp;
- long long lcounter; /* long counter for 64 bit fields */
int ret = 0;
might_sleep();
@@ -1871,18 +1884,9 @@
}
switch (field) {
- 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;
+ goto balance_counter; /* be still, gcc */
}
xfs_icsb_unlock_cntr(icsbp);
preempt_enable();