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9185 metaslab_verify_weight_and_frag() shouldn't cause side-effects #9282

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Sep 5, 2019
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9185 metaslab_verify_weight_and_frag() shouldn't cause side-effects #9282

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39 changes: 24 additions & 15 deletions module/zfs/metaslab.c
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Original file line number Diff line number Diff line change
Expand Up @@ -289,8 +289,8 @@ int zfs_metaslab_mem_limit = 25;
*/
unsigned long zfs_metaslab_max_size_cache_sec = 3600; /* 1 hour */

static uint64_t metaslab_weight(metaslab_t *);
static void metaslab_set_fragmentation(metaslab_t *);
static uint64_t metaslab_weight(metaslab_t *, boolean_t);
static void metaslab_set_fragmentation(metaslab_t *, boolean_t);
static void metaslab_free_impl(vdev_t *, uint64_t, uint64_t, boolean_t);
static void metaslab_check_free_impl(vdev_t *, uint64_t, uint64_t);

Expand Down Expand Up @@ -1845,13 +1845,19 @@ metaslab_verify_weight_and_frag(metaslab_t *msp)
msp->ms_fragmentation = 0;

/*
* This function is used for verification purposes. Regardless of
* whether metaslab_weight() thinks this metaslab should be active or
* not, we want to ensure that the actual weight (and therefore the
* value of ms_weight) would be the same if it was to be recalculated
* at this point.
* This function is used for verification purposes and thus should
* not introduce any side-effects/mutations on the system's state.
*
* Regardless of whether metaslab_weight() thinks this metaslab
* should be active or not, we want to ensure that the actual weight
* (and therefore the value of ms_weight) would be the same if it
* was to be recalculated at this point.
*
* In addition we set the nodirty flag so metaslab_weight() does
* not dirty the metaslab for future TXGs (e.g. when trying to
* force condensing to upgrade the metaslab spacemaps).
*/
msp->ms_weight = metaslab_weight(msp) | was_active;
msp->ms_weight = metaslab_weight(msp, B_TRUE) | was_active;

VERIFY3U(max_segsize, ==, msp->ms_max_size);

Expand Down Expand Up @@ -2335,7 +2341,7 @@ metaslab_init(metaslab_group_t *mg, uint64_t id, uint64_t object,
ms->ms_trim = range_tree_create(NULL, NULL);

metaslab_group_add(mg, ms);
metaslab_set_fragmentation(ms);
metaslab_set_fragmentation(ms, B_FALSE);

/*
* If we're opening an existing pool (txg == 0) or creating
Expand Down Expand Up @@ -2497,7 +2503,7 @@ int zfs_frag_table[FRAGMENTATION_TABLE_SIZE] = {
* value should be in the range [0, 100].
*/
static void
metaslab_set_fragmentation(metaslab_t *msp)
metaslab_set_fragmentation(metaslab_t *msp, boolean_t nodirty)
{
spa_t *spa = msp->ms_group->mg_vd->vdev_spa;
uint64_t fragmentation = 0;
Expand Down Expand Up @@ -2532,9 +2538,11 @@ metaslab_set_fragmentation(metaslab_t *msp)
* be shutting down the pool. We don't want to dirty
* any data past this point so skip setting the condense
* flag. We can retry this action the next time the pool
* is imported.
* is imported. We also skip marking this metaslab for
* condensing if the caller has explicitly set nodirty.
*/
if (spa_writeable(spa) && txg < spa_final_dirty_txg(spa)) {
if (!nodirty &&
spa_writeable(spa) && txg < spa_final_dirty_txg(spa)) {
msp->ms_condense_wanted = B_TRUE;
vdev_dirty(vd, VDD_METASLAB, msp, txg + 1);
zfs_dbgmsg("txg %llu, requesting force condense: "
Expand Down Expand Up @@ -2831,16 +2839,17 @@ metaslab_should_allocate(metaslab_t *msp, uint64_t asize, boolean_t try_hard)

return (should_allocate);
}

static uint64_t
metaslab_weight(metaslab_t *msp)
metaslab_weight(metaslab_t *msp, boolean_t nodirty)
{
vdev_t *vd = msp->ms_group->mg_vd;
spa_t *spa = vd->vdev_spa;
uint64_t weight;

ASSERT(MUTEX_HELD(&msp->ms_lock));

metaslab_set_fragmentation(msp);
metaslab_set_fragmentation(msp, nodirty);

/*
* Update the maximum size. If the metaslab is loaded, this will
Expand Down Expand Up @@ -2881,7 +2890,7 @@ metaslab_recalculate_weight_and_sort(metaslab_t *msp)
/* note: we preserve the mask (e.g. indication of primary, etc..) */
uint64_t was_active = msp->ms_weight & METASLAB_ACTIVE_MASK;
metaslab_group_sort(msp->ms_group, msp,
metaslab_weight(msp) | was_active);
metaslab_weight(msp, B_FALSE) | was_active);
}

static int
Expand Down