bcachefs: Refactor filesystem usage accounting

Various filesystem usage counters are kept in percpu counters, with one
set per in flight journal buffer. Right now all the code that deals with
it assumes that there's only two buffers/sets of counters, but the
number of journal bufs is getting increased to 4 in the next patch - so
refactor that code to not assume a constant.

Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>

7 files changed, 48 insertions, 46 deletions

diff --git a/fs/bcachefs/bcachefs.h b/fs/bcachefs/bcachefs.h
index 6d54defcee58..bef798c59e3b 100644
--- a/fs/bcachefs/bcachefs.h
+++ b/fs/bcachefs/bcachefs.h
@@ -675,7 +675,7 @@ struct bch_fs {
 
 	seqcount_t			usage_lock;
 	struct bch_fs_usage		*usage_base;
-	struct bch_fs_usage __percpu	*usage[2];
+	struct bch_fs_usage __percpu	*usage[JOURNAL_BUF_NR];
 	struct bch_fs_usage __percpu	*usage_gc;
 
 	/* single element mempool: */
diff --git a/fs/bcachefs/btree_gc.c b/fs/bcachefs/btree_gc.c
index ac81c9b9a06a..6268ea637d19 100644
--- a/fs/bcachefs/btree_gc.c
+++ b/fs/bcachefs/btree_gc.c
@@ -603,7 +603,6 @@ static int bch2_gc_done(struct bch_fs *c,
 		struct genradix_iter dst_iter = genradix_iter_init(&c->stripes[0], 0);
 		struct genradix_iter src_iter = genradix_iter_init(&c->stripes[1], 0);
 		struct stripe *dst, *src;
-		unsigned i;
 
 		c->ec_stripes_heap.used = 0;
 
@@ -651,8 +650,8 @@ static int bch2_gc_done(struct bch_fs *c,
 		}
 	};
 
-	bch2_fs_usage_acc_to_base(c, 0);
-	bch2_fs_usage_acc_to_base(c, 1);
+	for (i = 0; i < ARRAY_SIZE(c->usage); i++)
+		bch2_fs_usage_acc_to_base(c, i);
 
 	bch2_dev_usage_from_buckets(c);
 
diff --git a/fs/bcachefs/buckets.c b/fs/bcachefs/buckets.c
index 1b1200c55134..e297101af3a1 100644
--- a/fs/bcachefs/buckets.c
+++ b/fs/bcachefs/buckets.c
@@ -142,8 +142,8 @@ void bch2_fs_usage_initialize(struct bch_fs *c)
 	percpu_down_write(&c->mark_lock);
 	usage = c->usage_base;
 
-	bch2_fs_usage_acc_to_base(c, 0);
-	bch2_fs_usage_acc_to_base(c, 1);
+	for (i = 0; i < ARRAY_SIZE(c->usage); i++)
+		bch2_fs_usage_acc_to_base(c, i);
 
 	for (i = 0; i < BCH_REPLICAS_MAX; i++)
 		usage->reserved += usage->persistent_reserved[i];
@@ -207,13 +207,13 @@ static inline struct bch_fs_usage *fs_usage_ptr(struct bch_fs *c,
 {
 	return this_cpu_ptr(gc
 			    ? c->usage_gc
-			    : c->usage[journal_seq & 1]);
+			    : c->usage[journal_seq & JOURNAL_BUF_MASK]);
 }
 
 u64 bch2_fs_usage_read_one(struct bch_fs *c, u64 *v)
 {
 	ssize_t offset = v - (u64 *) c->usage_base;
-	unsigned seq;
+	unsigned i, seq;
 	u64 ret;
 
 	BUG_ON(offset < 0 || offset >= fs_usage_u64s(c));
@@ -221,9 +221,10 @@ u64 bch2_fs_usage_read_one(struct bch_fs *c, u64 *v)
 
 	do {
 		seq = read_seqcount_begin(&c->usage_lock);
-		ret = *v +
-			percpu_u64_get((u64 __percpu *) c->usage[0] + offset) +
-			percpu_u64_get((u64 __percpu *) c->usage[1] + offset);
+		ret = *v;
+
+		for (i = 0; i < ARRAY_SIZE(c->usage); i++)
+			ret += percpu_u64_get((u64 __percpu *) c->usage[i] + offset);
 	} while (read_seqcount_retry(&c->usage_lock, seq));
 
 	return ret;
@@ -232,7 +233,7 @@ u64 bch2_fs_usage_read_one(struct bch_fs *c, u64 *v)
 struct bch_fs_usage *bch2_fs_usage_read(struct bch_fs *c)
 {
 	struct bch_fs_usage *ret;
-	unsigned seq, v, u64s = fs_usage_u64s(c);
+	unsigned seq, i, v, u64s = fs_usage_u64s(c);
 retry:
 	ret = kmalloc(u64s * sizeof(u64), GFP_NOFS);
 	if (unlikely(!ret))
@@ -251,8 +252,8 @@ retry:
 	do {
 		seq = read_seqcount_begin(&c->usage_lock);
 		memcpy(ret, c->usage_base, u64s * sizeof(u64));
-		acc_u64s_percpu((u64 *) ret, (u64 __percpu *) c->usage[0], u64s);
-		acc_u64s_percpu((u64 *) ret, (u64 __percpu *) c->usage[1], u64s);
+		for (i = 0; i < ARRAY_SIZE(c->usage); i++)
+			acc_u64s_percpu((u64 *) ret, (u64 __percpu *) c->usage[i], u64s);
 	} while (read_seqcount_retry(&c->usage_lock, seq));
 
 	return ret;
@@ -262,7 +263,7 @@ void bch2_fs_usage_acc_to_base(struct bch_fs *c, unsigned idx)
 {
 	unsigned u64s = fs_usage_u64s(c);
 
-	BUG_ON(idx >= 2);
+	BUG_ON(idx >= ARRAY_SIZE(c->usage));
 
 	preempt_disable();
 	write_seqcount_begin(&c->usage_lock);
diff --git a/fs/bcachefs/journal_types.h b/fs/bcachefs/journal_types.h
index 4640bb8687cc..00c3de77e823 100644
--- a/fs/bcachefs/journal_types.h
+++ b/fs/bcachefs/journal_types.h
@@ -11,6 +11,10 @@
 
 struct journal_res;
 
+#define JOURNAL_BUF_BITS	1
+#define JOURNAL_BUF_NR		(1U << JOURNAL_BUF_BITS)
+#define JOURNAL_BUF_MASK	(JOURNAL_BUF_NR - 1)
+
 /*
  * We put two of these in struct journal; we used them for writes to the
  * journal that are being staged or in flight.
diff --git a/fs/bcachefs/replicas.c b/fs/bcachefs/replicas.c
index 91518c0d6794..00a197b65e0b 100644
--- a/fs/bcachefs/replicas.c
+++ b/fs/bcachefs/replicas.c
@@ -275,53 +275,55 @@ static void __replicas_table_update_pcpu(struct bch_fs_usage __percpu *dst_p,
 static int replicas_table_update(struct bch_fs *c,
 				 struct bch_replicas_cpu *new_r)
 {
-	struct bch_fs_usage __percpu *new_usage[2] = { NULL, NULL };
+	struct bch_fs_usage __percpu *new_usage[JOURNAL_BUF_NR];
 	struct bch_fs_usage *new_scratch = NULL;
 	struct bch_fs_usage __percpu *new_gc = NULL;
 	struct bch_fs_usage *new_base = NULL;
-	unsigned bytes = sizeof(struct bch_fs_usage) +
+	unsigned i, bytes = sizeof(struct bch_fs_usage) +
 		sizeof(u64) * new_r->nr;
-	int ret = -ENOMEM;
+	int ret = 0;
+
+	memset(new_usage, 0, sizeof(new_usage));
+
+	for (i = 0; i < ARRAY_SIZE(new_usage); i++)
+		if (!(new_usage[i] = __alloc_percpu_gfp(bytes,
+					sizeof(u64), GFP_NOIO)))
+			goto err;
 
 	if (!(new_base = kzalloc(bytes, GFP_NOIO)) ||
-	    !(new_usage[0] = __alloc_percpu_gfp(bytes, sizeof(u64),
-						GFP_NOIO)) ||
-	    !(new_usage[1] = __alloc_percpu_gfp(bytes, sizeof(u64),
-						GFP_NOIO)) ||
 	    !(new_scratch  = kmalloc(bytes, GFP_NOIO)) ||
 	    (c->usage_gc &&
-	     !(new_gc = __alloc_percpu_gfp(bytes, sizeof(u64), GFP_NOIO)))) {
-		bch_err(c, "error updating replicas table: memory allocation failure");
+	     !(new_gc = __alloc_percpu_gfp(bytes, sizeof(u64), GFP_NOIO))))
 		goto err;
-	}
 
+	for (i = 0; i < ARRAY_SIZE(new_usage); i++)
+		if (c->usage[i])
+			__replicas_table_update_pcpu(new_usage[i], new_r,
+						     c->usage[i], &c->replicas);
 	if (c->usage_base)
 		__replicas_table_update(new_base,		new_r,
 					c->usage_base,		&c->replicas);
-	if (c->usage[0])
-		__replicas_table_update_pcpu(new_usage[0],	new_r,
-					     c->usage[0],	&c->replicas);
-	if (c->usage[1])
-		__replicas_table_update_pcpu(new_usage[1],	new_r,
-					     c->usage[1],	&c->replicas);
 	if (c->usage_gc)
 		__replicas_table_update_pcpu(new_gc,		new_r,
 					     c->usage_gc,	&c->replicas);
 
+	for (i = 0; i < ARRAY_SIZE(new_usage); i++)
+		swap(c->usage[i],	new_usage[i]);
 	swap(c->usage_base,	new_base);
-	swap(c->usage[0],	new_usage[0]);
-	swap(c->usage[1],	new_usage[1]);
 	swap(c->usage_scratch,	new_scratch);
 	swap(c->usage_gc,	new_gc);
 	swap(c->replicas,	*new_r);
-	ret = 0;
-err:
+out:
 	free_percpu(new_gc);
 	kfree(new_scratch);
 	free_percpu(new_usage[1]);
 	free_percpu(new_usage[0]);
 	kfree(new_base);
 	return ret;
+err:
+	bch_err(c, "error updating replicas table: memory allocation failure");
+	ret = -ENOMEM;
+	goto out;
 }
 
 static unsigned reserve_journal_replicas(struct bch_fs *c,
@@ -496,9 +498,7 @@ int bch2_replicas_gc_end(struct bch_fs *c, int ret)
 		struct bch_replicas_cpu n;
 
 		if (!__replicas_has_entry(&c->replicas_gc, e) &&
-		    (c->usage_base->replicas[i] ||
-		     percpu_u64_get(&c->usage[0]->replicas[i]) ||
-		     percpu_u64_get(&c->usage[1]->replicas[i]))) {
+		    bch2_fs_usage_read_one(c, &c->usage_base->replicas[i])) {
 			n = cpu_replicas_add_entry(&c->replicas_gc, e);
 			if (!n.entries) {
 				ret = -ENOSPC;
@@ -603,9 +603,7 @@ retry:
 			cpu_replicas_entry(&c->replicas, i);
 
 		if (e->data_type == BCH_DATA_journal ||
-		    c->usage_base->replicas[i] ||
-		    percpu_u64_get(&c->usage[0]->replicas[i]) ||
-		    percpu_u64_get(&c->usage[1]->replicas[i]))
+		    bch2_fs_usage_read_one(c, &c->usage_base->replicas[i]))
 			memcpy(cpu_replicas_entry(&new, new.nr++),
 			       e, new.entry_size);
 	}
diff --git a/fs/bcachefs/super-io.c b/fs/bcachefs/super-io.c
index f969b5df0b23..ffd219091ea6 100644
--- a/fs/bcachefs/super-io.c
+++ b/fs/bcachefs/super-io.c
@@ -992,10 +992,10 @@ bch2_journal_super_entries_add_common(struct bch_fs *c,
 	percpu_down_write(&c->mark_lock);
 
 	if (!journal_seq) {
-		bch2_fs_usage_acc_to_base(c, 0);
-		bch2_fs_usage_acc_to_base(c, 1);
+		for (i = 0; i < ARRAY_SIZE(c->usage); i++)
+			bch2_fs_usage_acc_to_base(c, i);
 	} else {
-		bch2_fs_usage_acc_to_base(c, journal_seq & 1);
+		bch2_fs_usage_acc_to_base(c, journal_seq & JOURNAL_BUF_MASK);
 	}
 
 	{
diff --git a/fs/bcachefs/super.c b/fs/bcachefs/super.c
index e3bbd0b0d698..748350589eb8 100644
--- a/fs/bcachefs/super.c
+++ b/fs/bcachefs/super.c
@@ -475,8 +475,8 @@ static void __bch2_fs_free(struct bch_fs *c)
 	bch2_journal_entries_free(&c->journal_entries);
 	percpu_free_rwsem(&c->mark_lock);
 	kfree(c->usage_scratch);
-	free_percpu(c->usage[1]);
-	free_percpu(c->usage[0]);
+	for (i = 0; i < ARRAY_SIZE(c->usage); i++)
+		free_percpu(c->usage[i]);
 	kfree(c->usage_base);
 
 	if (c->btree_iters_bufs)