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bcachefs: Better use of locking helpers

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Held btree locks are tracked in btree_path->nodes_locked and
btree_path->nodes_intent_locked. Upcoming patches are going to change
the representation in struct btree_path, so this patch switches to
proper helpers instead of direct access to these fields.

Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
This commit is contained in:
Kent Overstreet 2022-08-21 18:17:51 -04:00 committed by Kent Overstreet
parent 8e5696698d
commit d4263e5638
4 changed files with 58 additions and 39 deletions
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6
fs/bcachefs/btree_iter.c
View File

@ -348,7 +348,7 @@ void bch2_assert_pos_locked(struct btree_trans *trans, enum btree_id id,
if (cmp < 0)
continue;
if (!(path->nodes_locked & 1) ||
if (!btree_node_locked(path, 0) ||
!path->should_be_locked)
continue;
@ -3053,8 +3053,8 @@ void bch2_btree_trans_to_text(struct printbuf *out, struct btree_trans *trans)
for (l = 0; l < BTREE_MAX_DEPTH; l++) {
if (btree_node_locked(path, l) &&
!IS_ERR_OR_NULL(b = (void *) READ_ONCE(path->l[l].b))) {
prt_printf(out, " %s l=%u ",
btree_node_intent_locked(path, l) ? "i" : "r", l);
prt_printf(out, " %c l=%u ",
lock_types[btree_node_locked_type(path, l)], l);
bch2_btree_path_node_to_text(out, b, path->cached);
prt_printf(out, "\n");
}

20
fs/bcachefs/btree_locking.c
View File

@ -61,6 +61,16 @@ void __bch2_btree_node_lock_write(struct btree_trans *trans, struct btree *b)
six_lock_readers_add(&b->c.lock, readers);
}
static inline bool path_has_read_locks(struct btree_path *path)
{
unsigned l;
for (l = 0; l < BTREE_MAX_DEPTH; l++)
if (btree_node_read_locked(path, l))
return true;
return false;
}
/* Slowpath: */
int __bch2_btree_node_lock(struct btree_trans *trans,
struct btree_path *path,
@ -91,7 +101,7 @@ int __bch2_btree_node_lock(struct btree_trans *trans,
* already have read locked - deadlock:
*/
if (type == SIX_LOCK_intent &&
linked->nodes_locked != linked->nodes_intent_locked) {
path_has_read_locks(linked)) {
reason = 1;
goto deadlock;
}
@ -121,7 +131,7 @@ int __bch2_btree_node_lock(struct btree_trans *trans,
* another path has possible descendants locked of the node
* we're about to lock, it must have the ancestors locked too:
*/
if (level > __fls(linked->nodes_locked)) {
if (level > btree_path_highest_level_locked(linked)) {
reason = 5;
goto deadlock;
}
@ -254,7 +264,7 @@ bool bch2_btree_node_upgrade(struct btree_trans *trans,
trace_btree_node_upgrade_fail(trans, _RET_IP_, path, level);
return false;
success:
mark_btree_node_intent_locked(trans, path, level);
mark_btree_node_locked_noreset(path, level, SIX_LOCK_intent);
return true;
}
@ -370,13 +380,13 @@ void __bch2_btree_path_downgrade(struct btree_trans *trans,
path->locks_want = new_locks_want;
while (path->nodes_locked &&
(l = __fls(path->nodes_locked)) >= path->locks_want) {
(l = btree_path_highest_level_locked(path)) >= path->locks_want) {
if (l > path->level) {
btree_node_unlock(trans, path, l);
} else {
if (btree_node_intent_locked(path, l)) {
six_lock_downgrade(&path->l[l].b->c.lock);
path->nodes_intent_locked ^= 1 << l;
mark_btree_node_locked_noreset(path, l, SIX_LOCK_read);
}
break;
}

50
fs/bcachefs/btree_locking.h
View File

@ -61,27 +61,30 @@ static inline bool btree_node_read_locked(struct btree_path *path,
static inline bool btree_node_locked(struct btree_path *path, unsigned level)
{
return path->nodes_locked & (1 << level);
return btree_node_locked_type(path, level) != BTREE_NODE_UNLOCKED;
}
static inline void mark_btree_node_unlocked(struct btree_path *path,
unsigned level)
{
path->nodes_locked &= ~(1 << level);
path->nodes_intent_locked &= ~(1 << level);
}
static inline void mark_btree_node_locked_noreset(struct btree_trans *trans,
struct btree_path *path,
static inline void mark_btree_node_locked_noreset(struct btree_path *path,
unsigned level,
enum six_lock_type type)
enum btree_node_locked_type type)
{
/* relying on this to avoid a branch */
BUILD_BUG_ON(SIX_LOCK_read != 0);
BUILD_BUG_ON(SIX_LOCK_intent != 1);
path->nodes_locked |= 1 << level;
path->nodes_intent_locked |= type << level;
path->nodes_locked &= ~(1 << level);
path->nodes_intent_locked &= ~(1 << level);
if (type != BTREE_NODE_UNLOCKED) {
path->nodes_locked |= 1 << level;
path->nodes_intent_locked |= type << level;
}
}
static inline void mark_btree_node_unlocked(struct btree_path *path,
unsigned level)
{
mark_btree_node_locked_noreset(path, level, BTREE_NODE_UNLOCKED);
}
static inline void mark_btree_node_locked(struct btree_trans *trans,
@ -89,19 +92,12 @@ static inline void mark_btree_node_locked(struct btree_trans *trans,
unsigned level,
enum six_lock_type type)
{
mark_btree_node_locked_noreset(trans, path, level, type);
mark_btree_node_locked_noreset(path, level, type);
#ifdef CONFIG_BCACHEFS_LOCK_TIME_STATS
path->l[level].lock_taken_time = ktime_get_ns();
#endif
}
static inline void mark_btree_node_intent_locked(struct btree_trans *trans,
struct btree_path *path,
unsigned level)
{
mark_btree_node_locked_noreset(trans, path, level, SIX_LOCK_intent);
}
static inline enum six_lock_type __btree_lock_want(struct btree_path *path, int level)
{
return level < path->locks_want
@ -164,13 +160,23 @@ static inline void btree_node_unlock(struct btree_trans *trans,
mark_btree_node_unlocked(path, level);
}
static inline int btree_path_lowest_level_locked(struct btree_path *path)
{
return __ffs(path->nodes_locked);
}
static inline int btree_path_highest_level_locked(struct btree_path *path)
{
return __fls(path->nodes_locked);
}
static inline void __bch2_btree_path_unlock(struct btree_trans *trans,
struct btree_path *path)
{
btree_path_set_dirty(path, BTREE_ITER_NEED_RELOCK);
while (path->nodes_locked)
btree_node_unlock(trans, path, __ffs(path->nodes_locked));
btree_node_unlock(trans, path, btree_path_lowest_level_locked(path));
}
/*

21
fs/bcachefs/btree_update_leaf.c
View File

@ -747,11 +747,12 @@ static inline void path_upgrade_readers(struct btree_trans *trans, struct btree_
static inline void upgrade_readers(struct btree_trans *trans, struct btree_path *path)
{
struct btree *b = path_l(path)->b;
unsigned l;
do {
if (path->nodes_locked &&
path->nodes_locked != path->nodes_intent_locked)
path_upgrade_readers(trans, path);
for (l = 0; l < BTREE_MAX_DEPTH; l++)
if (btree_node_read_locked(path, l))
path_upgrade_readers(trans, path);
} while ((path = prev_btree_path(trans, path)) &&
path_l(path)->b == b);
}
@ -770,11 +771,13 @@ static inline void normalize_read_intent_locks(struct btree_trans *trans)
? trans->paths + trans->sorted[i + 1]
: NULL;
if (path->nodes_locked) {
if (path->nodes_intent_locked)
nr_intent++;
else
nr_read++;
switch (btree_node_locked_type(path, path->level)) {
case BTREE_NODE_READ_LOCKED:
nr_read++;
break;
case BTREE_NODE_INTENT_LOCKED:
nr_intent++;
break;
}
if (!next || path_l(path)->b != path_l(next)->b) {
@ -797,7 +800,7 @@ static inline bool have_conflicting_read_lock(struct btree_trans *trans, struct
//if (path == pos)
// break;
if (path->nodes_locked != path->nodes_intent_locked &&
if (btree_node_read_locked(path, path->level) &&
!bch2_btree_path_upgrade(trans, path, path->level + 1))
return true;
}