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-rw-r--r--fs/bcachefs/nocow_locking.c144
1 files changed, 144 insertions, 0 deletions
diff --git a/fs/bcachefs/nocow_locking.c b/fs/bcachefs/nocow_locking.c
new file mode 100644
index 0000000000..3c21981a4a
--- /dev/null
+++ b/fs/bcachefs/nocow_locking.c
@@ -0,0 +1,144 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include "bcachefs.h"
+#include "bkey_methods.h"
+#include "nocow_locking.h"
+#include "util.h"
+
+#include <linux/closure.h>
+
+bool bch2_bucket_nocow_is_locked(struct bucket_nocow_lock_table *t, struct bpos bucket)
+{
+ u64 dev_bucket = bucket_to_u64(bucket);
+ struct nocow_lock_bucket *l = bucket_nocow_lock(t, dev_bucket);
+ unsigned i;
+
+ for (i = 0; i < ARRAY_SIZE(l->b); i++)
+ if (l->b[i] == dev_bucket && atomic_read(&l->l[i]))
+ return true;
+ return false;
+}
+
+#define sign(v) (v < 0 ? -1 : v > 0 ? 1 : 0)
+
+void bch2_bucket_nocow_unlock(struct bucket_nocow_lock_table *t, struct bpos bucket, int flags)
+{
+ u64 dev_bucket = bucket_to_u64(bucket);
+ struct nocow_lock_bucket *l = bucket_nocow_lock(t, dev_bucket);
+ int lock_val = flags ? 1 : -1;
+ unsigned i;
+
+ for (i = 0; i < ARRAY_SIZE(l->b); i++)
+ if (l->b[i] == dev_bucket) {
+ int v = atomic_sub_return(lock_val, &l->l[i]);
+
+ BUG_ON(v && sign(v) != lock_val);
+ if (!v)
+ closure_wake_up(&l->wait);
+ return;
+ }
+
+ BUG();
+}
+
+bool __bch2_bucket_nocow_trylock(struct nocow_lock_bucket *l,
+ u64 dev_bucket, int flags)
+{
+ int v, lock_val = flags ? 1 : -1;
+ unsigned i;
+
+ spin_lock(&l->lock);
+
+ for (i = 0; i < ARRAY_SIZE(l->b); i++)
+ if (l->b[i] == dev_bucket)
+ goto got_entry;
+
+ for (i = 0; i < ARRAY_SIZE(l->b); i++)
+ if (!atomic_read(&l->l[i])) {
+ l->b[i] = dev_bucket;
+ goto take_lock;
+ }
+fail:
+ spin_unlock(&l->lock);
+ return false;
+got_entry:
+ v = atomic_read(&l->l[i]);
+ if (lock_val > 0 ? v < 0 : v > 0)
+ goto fail;
+take_lock:
+ v = atomic_read(&l->l[i]);
+ /* Overflow? */
+ if (v && sign(v + lock_val) != sign(v))
+ goto fail;
+
+ atomic_add(lock_val, &l->l[i]);
+ spin_unlock(&l->lock);
+ return true;
+}
+
+void __bch2_bucket_nocow_lock(struct bucket_nocow_lock_table *t,
+ struct nocow_lock_bucket *l,
+ u64 dev_bucket, int flags)
+{
+ if (!__bch2_bucket_nocow_trylock(l, dev_bucket, flags)) {
+ struct bch_fs *c = container_of(t, struct bch_fs, nocow_locks);
+ u64 start_time = local_clock();
+
+ __closure_wait_event(&l->wait, __bch2_bucket_nocow_trylock(l, dev_bucket, flags));
+ bch2_time_stats_update(&c->times[BCH_TIME_nocow_lock_contended], start_time);
+ }
+}
+
+void bch2_nocow_locks_to_text(struct printbuf *out, struct bucket_nocow_lock_table *t)
+
+{
+ unsigned i, nr_zero = 0;
+ struct nocow_lock_bucket *l;
+
+ for (l = t->l; l < t->l + ARRAY_SIZE(t->l); l++) {
+ unsigned v = 0;
+
+ for (i = 0; i < ARRAY_SIZE(l->l); i++)
+ v |= atomic_read(&l->l[i]);
+
+ if (!v) {
+ nr_zero++;
+ continue;
+ }
+
+ if (nr_zero)
+ prt_printf(out, "(%u empty entries)\n", nr_zero);
+ nr_zero = 0;
+
+ for (i = 0; i < ARRAY_SIZE(l->l); i++) {
+ int v = atomic_read(&l->l[i]);
+ if (v) {
+ bch2_bpos_to_text(out, u64_to_bucket(l->b[i]));
+ prt_printf(out, ": %s %u ", v < 0 ? "copy" : "update", abs(v));
+ }
+ }
+ prt_newline(out);
+ }
+
+ if (nr_zero)
+ prt_printf(out, "(%u empty entries)\n", nr_zero);
+}
+
+void bch2_fs_nocow_locking_exit(struct bch_fs *c)
+{
+ struct bucket_nocow_lock_table *t = &c->nocow_locks;
+
+ for (struct nocow_lock_bucket *l = t->l; l < t->l + ARRAY_SIZE(t->l); l++)
+ for (unsigned j = 0; j < ARRAY_SIZE(l->l); j++)
+ BUG_ON(atomic_read(&l->l[j]));
+}
+
+int bch2_fs_nocow_locking_init(struct bch_fs *c)
+{
+ struct bucket_nocow_lock_table *t = &c->nocow_locks;
+
+ for (struct nocow_lock_bucket *l = t->l; l < t->l + ARRAY_SIZE(t->l); l++)
+ spin_lock_init(&l->lock);
+
+ return 0;
+}