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Refactor level_count and protect with seqcount

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We were manually manipulating the level counts in the super in a bunch
of places under the manifest rwsem.  This refactors them into simple get
and add functions.  We protect them with a seqcount so that we'll be
able read them without blocking (from trans hold attempts).  We also add
a helper for testing that a level is full because we already used
different comparisons in two call sites.

Signed-off-by: Zach Brown <zab@versity.com>
This commit is contained in:
Zach Brown
2017-04-18 13:44:53 -07:00
parent 2083793ae0
commit c21dc4ec20
1 changed files with 36 additions and 6 deletions
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kmod/src/manifest.c
+36 -6
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@@ -43,6 +43,7 @@
struct manifest {
struct rw_semaphore rwsem;
seqcount_t seqcount;
struct scoutfs_treap *treap;
u8 nr_levels;
@@ -127,6 +128,35 @@ static bool cmp_range_ment(struct kvec *key, struct kvec *end,
return scoutfs_kvec_cmp_overlap(key, end, first, last);
}
static u64 get_level_count(struct manifest *mani,
struct scoutfs_super_block *super, u8 level)
{
unsigned int sc;
u64 count;
do {
sc = read_seqcount_begin(&mani->seqcount);
count = le64_to_cpu(super->manifest.level_counts[level]);
} while (read_seqcount_retry(&mani->seqcount, sc));
return count;
}
static void add_level_count(struct manifest *mani,
struct scoutfs_super_block *super, u8 level,
s64 val)
{
write_seqcount_begin(&mani->seqcount);
le64_add_cpu(&super->manifest.level_counts[level], val);
write_seqcount_end(&mani->seqcount);
}
static bool level_full(struct manifest *mani,
struct scoutfs_super_block *super, u8 level)
{
return get_level_count(mani, super, level) > mani->level_limits[level];
}
/*
* Insert a new manifest entry in the treap. The treap allocates a new
* node for us and we fill it.
@@ -169,10 +199,9 @@ int scoutfs_manifest_add(struct super_block *sb, struct kvec *first,
ret = PTR_ERR(ment);
} else {
mani->nr_levels = max_t(u8, mani->nr_levels, level + 1);
le64_add_cpu(&super->manifest.level_counts[level], 1);
add_level_count(mani, super, level, 1);
if (le64_to_cpu(super->manifest.level_counts[level]) >
mani->level_limits[level])
if (level_full(mani, super, level))
scoutfs_compact_kick(sb);
ret = 0;
@@ -221,7 +250,7 @@ int scoutfs_manifest_del(struct super_block *sb, struct kvec *first, u64 seq,
ret = scoutfs_treap_delete(mani->treap, &skey);
if (ret == 0)
le64_add_cpu(&super->manifest.level_counts[level], -1ULL);
add_level_count(mani, super, level, -1ULL);
return ret;
}
@@ -634,8 +663,7 @@ int scoutfs_manifest_next_compact(struct super_block *sb, void *data)
down_write(&mani->rwsem);
for (level = mani->nr_levels - 1; level >= 0; level--) {
if (le64_to_cpu(super->manifest.level_counts[level]) >=
mani->level_limits[level])
if (level_full(mani, super, level))
break;
}
@@ -838,6 +866,8 @@ int scoutfs_manifest_setup(struct super_block *sb)
return -ENOMEM;
init_rwsem(&mani->rwsem);
seqcount_init(&mani->seqcount);
mani->treap = scoutfs_treap_alloc(sb, &manifest_treap_ops,
&super->manifest.root);
if (!mani->treap) {