bcachefs: percpu utility code

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/buckets.c

@@ -1005,10 +1005,7 @@ void bch2_mark_update(struct btree_insert *trans,
 
 static u64 bch2_recalc_sectors_available(struct bch_fs *c)
 {
-	int cpu;
-
-	for_each_possible_cpu(cpu)
-		per_cpu_ptr(c->pcpu, cpu)->sectors_available = 0;
+	percpu_u64_set(&c->pcpu->sectors_available, 0);
 
 	return avail_factor(bch2_fs_sectors_free(c));
 }

fs/bcachefs/replicas.c

@@ -426,14 +426,12 @@ int bch2_replicas_gc_end(struct bch_fs *c, int ret)
 		struct bch_replicas_entry *e =
 			cpu_replicas_entry(&c->replicas, i);
 		struct bch_replicas_cpu n;
-		u64 v = 0;
-		int cpu;
+		u64 v;
 
 		if (__replicas_has_entry(&c->replicas_gc, e))
 			continue;
 
-		for_each_possible_cpu(cpu)
-			v += *per_cpu_ptr(&c->usage[0]->data[i], cpu);
+		v = percpu_u64_get(&c->usage[0]->data[i]);
 		if (!v)
 			continue;
 

fs/bcachefs/sysfs.c

@@ -893,20 +893,15 @@ static const char * const bch2_rw[] = {
 static ssize_t show_dev_iodone(struct bch_dev *ca, char *buf)
 {
 	struct printbuf out = _PBUF(buf, PAGE_SIZE);
-	int rw, i, cpu;
+	int rw, i;
 
 	for (rw = 0; rw < 2; rw++) {
 		pr_buf(&out, "%s:\n", bch2_rw[rw]);
 
-		for (i = 1; i < BCH_DATA_NR; i++) {
-			u64 n = 0;
-
-			for_each_possible_cpu(cpu)
-				n += per_cpu_ptr(ca->io_done, cpu)->sectors[rw][i];
-
+		for (i = 1; i < BCH_DATA_NR; i++)
 			pr_buf(&out, "%-12s:%12llu\n",
-			       bch2_data_types[i], n << 9);
-		}
+			       bch2_data_types[i],
+			       percpu_u64_get(&ca->io_done->sectors[rw][i]) << 9);
 	}
 
 	return out.pos - buf;

fs/bcachefs/util.h

@@ -12,6 +12,7 @@
 #include <linux/llist.h>
 #include <linux/log2.h>
 #include <linux/percpu.h>
+#include <linux/preempt.h>
 #include <linux/ratelimit.h>
 #include <linux/slab.h>
 #include <linux/vmalloc.h>
@@ -701,6 +702,28 @@ do {									\
 	}								\
 } while (0)
 
+static inline u64 percpu_u64_get(u64 __percpu *src)
+{
+	u64 ret = 0;
+	int cpu;
+
+	for_each_possible_cpu(cpu)
+		ret += *per_cpu_ptr(src, cpu);
+	return ret;
+}
+
+static inline void percpu_u64_set(u64 __percpu *dst, u64 src)
+{
+	int cpu;
+
+	for_each_possible_cpu(cpu)
+		*per_cpu_ptr(dst, cpu) = 0;
+
+	preempt_disable();
+	*this_cpu_ptr(dst) = src;
+	preempt_enable();
+}
+
 static inline void acc_u64s(u64 *acc, const u64 *src, unsigned nr)
 {
 	unsigned i;