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bcachefs: is_ancestor bitmap 

Further optimization for bch2_snapshot_is_ancestor(). We add a small
inline bitmap to snapshot_t, which indicates which of the next 128
snapshot IDs are ancestors of the current id - eliminating the last few
iterations of the loop in bch2_snapshot_is_ancestor().

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
This commit is contained in:
Kent Overstreet 2023-07-13 02:43:29 -04:00
parent 5eaa76d813
commit 6132c84cac
2 changed files with 18 additions and 8 deletions
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23
fs/bcachefs/subvolume.c
View File

@ -28,17 +28,22 @@ static inline u32 get_ancestor_below(struct snapshot_table *t, u32 id, u32 ances
bool bch2_snapshot_is_ancestor(struct bch_fs *c, u32 id, u32 ancestor)
{
struct snapshot_table *t;
bool ret;
EBUG_ON(c->curr_recovery_pass <= BCH_RECOVERY_PASS_check_snapshots);
rcu_read_lock();
t = rcu_dereference(c->snapshots);
while (id && id < ancestor)
while (id && id < ancestor - IS_ANCESTOR_BITMAP)
id = get_ancestor_below(t, id, ancestor);
ret = id && id < ancestor
? test_bit(ancestor - id - 1, __snapshot_t(t, id)->is_ancestor)
: id == ancestor;
rcu_read_unlock();
return id == ancestor;
return ret;
}
static bool bch2_snapshot_is_ancestor_early(struct bch_fs *c, u32 id, u32 ancestor)
@ -289,11 +294,12 @@ int bch2_mark_snapshot(struct btree_trans *trans,
{
struct bch_fs *c = trans->c;
struct snapshot_t *t;
u32 id = new.k->p.offset;
int ret = 0;
mutex_lock(&c->snapshot_table_lock);
t = snapshot_t_mut(c, new.k->p.offset);
t = snapshot_t_mut(c, id);
if (!t) {
ret = -BCH_ERR_ENOMEM_mark_snapshot;
goto err;
@ -301,6 +307,7 @@ int bch2_mark_snapshot(struct btree_trans *trans,
if (new.k->type == KEY_TYPE_snapshot) {
struct bkey_s_c_snapshot s = bkey_s_c_to_snapshot(new);
u32 parent = id;
t->parent = le32_to_cpu(s.v->parent);
t->children[0] = le32_to_cpu(s.v->children[0]);
@ -320,14 +327,14 @@ int bch2_mark_snapshot(struct btree_trans *trans,
t->skip[2] = 0;
}
while ((parent = bch2_snapshot_parent_early(c, parent)) &&
parent - id - 1 < IS_ANCESTOR_BITMAP)
__set_bit(parent - id - 1, t->is_ancestor);
if (BCH_SNAPSHOT_DELETED(s.v))
set_bit(BCH_FS_HAVE_DELETED_SNAPSHOTS, &c->flags);
} else {
t->parent = 0;
t->children[0] = 0;
t->children[1] = 0;
t->subvol = 0;
t->tree = 0;
memset(t, 0, sizeof(*t));
}
err:
mutex_unlock(&c->snapshot_table_lock);

3
fs/bcachefs/subvolume_types.h
View File

@ -6,6 +6,8 @@
typedef DARRAY(u32) snapshot_id_list;
#define IS_ANCESTOR_BITMAP 128
struct snapshot_t {
u32 parent;
u32 skip[3];
@ -14,6 +16,7 @@ struct snapshot_t {
u32 subvol; /* Nonzero only if a subvolume points to this node: */
u32 tree;
u32 equiv;
unsigned long is_ancestor[BITS_TO_LONGS(IS_ANCESTOR_BITMAP)];
};
struct snapshot_table {