bcachefs: Change allocations for ec stripes to blocking

We don't want writes to not get erasure coded just because the allocator
temporarily wasn't keeping up.

However, it's not guaranteed that these allocations will ever succeed,
we can currently get stuck - especially if devices are different sizes -
we still have work to do in this area.
Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/alloc_foreground.c

@@ -446,16 +446,18 @@ bch2_bucket_alloc_set(struct bch_fs *c,
  * it's to a device we don't want:
  */
 
-static void bucket_alloc_from_stripe(struct bch_fs *c,
-				     struct open_buckets *ptrs,
-				     struct write_point *wp,
-				     struct bch_devs_mask *devs_may_alloc,
-				     u16 target,
-				     unsigned erasure_code,
-				     unsigned nr_replicas,
-				     unsigned *nr_effective,
-				     bool *have_cache,
-				     unsigned flags)
+static enum bucket_alloc_ret
+bucket_alloc_from_stripe(struct bch_fs *c,
+			 struct open_buckets *ptrs,
+			 struct write_point *wp,
+			 struct bch_devs_mask *devs_may_alloc,
+			 u16 target,
+			 unsigned erasure_code,
+			 unsigned nr_replicas,
+			 unsigned *nr_effective,
+			 bool *have_cache,
+			 unsigned flags,
+			 struct closure *cl)
 {
 	struct dev_alloc_list devs_sorted;
 	struct ec_stripe_head *h;
@@ -464,17 +466,19 @@ static void bucket_alloc_from_stripe(struct bch_fs *c,
 	unsigned i, ec_idx;
 
 	if (!erasure_code)
-		return;
+		return 0;
 
 	if (nr_replicas < 2)
-		return;
+		return 0;
 
 	if (ec_open_bucket(c, ptrs))
-		return;
+		return 0;
 
-	h = bch2_ec_stripe_head_get(c, target, 0, nr_replicas - 1);
+	h = bch2_ec_stripe_head_get(c, target, 0, nr_replicas - 1, cl);
+	if (IS_ERR(h))
+		return -PTR_ERR(h);
 	if (!h)
-		return;
+		return 0;
 
 	devs_sorted = bch2_dev_alloc_list(c, &wp->stripe, devs_may_alloc);
 
@@ -496,6 +500,7 @@ static void bucket_alloc_from_stripe(struct bch_fs *c,
 	atomic_inc(&h->s->pin);
 out_put_head:
 	bch2_ec_stripe_head_put(c, h);
+	return 0;
 }
 
 /* Sector allocator */
@@ -573,10 +578,13 @@ open_bucket_add_buckets(struct bch_fs *c,
 		}
 
 		if (!ec_open_bucket(c, ptrs)) {
-			bucket_alloc_from_stripe(c, ptrs, wp, &devs,
+			ret = bucket_alloc_from_stripe(c, ptrs, wp, &devs,
 						 target, erasure_code,
 						 nr_replicas, nr_effective,
-						 have_cache, flags);
+						 have_cache, flags, _cl);
+			if (ret == FREELIST_EMPTY ||
+			    ret == OPEN_BUCKETS_EMPTY)
+				return ret;
 			if (*nr_effective >= nr_replicas)
 				return 0;
 		}

fs/bcachefs/ec.c

@@ -1228,10 +1228,9 @@ struct ec_stripe_head *__bch2_ec_stripe_head_get(struct bch_fs *c,
 	return h;
 }
 
-/*
- * XXX: use a higher watermark for allocating open buckets here:
- */
-static int new_stripe_alloc_buckets(struct bch_fs *c, struct ec_stripe_head *h)
+static enum bucket_alloc_ret
+new_stripe_alloc_buckets(struct bch_fs *c, struct ec_stripe_head *h,
+			 struct closure *cl)
 {
 	struct bch_devs_mask devs;
 	struct open_bucket *ob;
@@ -1239,7 +1238,7 @@ static int new_stripe_alloc_buckets(struct bch_fs *c, struct ec_stripe_head *h)
 		min_t(unsigned, h->nr_active_devs,
 		      BCH_BKEY_PTRS_MAX) - h->redundancy;
 	bool have_cache = true;
-	int ret = 0;
+	enum bucket_alloc_ret ret = ALLOC_SUCCESS;
 
 	devs = h->devs;
 
@@ -1270,7 +1269,7 @@ static int new_stripe_alloc_buckets(struct bch_fs *c, struct ec_stripe_head *h)
 					    &have_cache,
 					    RESERVE_NONE,
 					    0,
-					    NULL);
+					    cl);
 		if (ret)
 			goto err;
 	}
@@ -1286,7 +1285,7 @@ static int new_stripe_alloc_buckets(struct bch_fs *c, struct ec_stripe_head *h)
 					    &have_cache,
 					    RESERVE_NONE,
 					    0,
-					    NULL);
+					    cl);
 		if (ret)
 			goto err;
 	}
@@ -1352,7 +1351,8 @@ static int get_stripe_key(struct bch_fs *c, u64 idx, struct ec_stripe_buf *strip
 struct ec_stripe_head *bch2_ec_stripe_head_get(struct bch_fs *c,
 					       unsigned target,
 					       unsigned algo,
-					       unsigned redundancy)
+					       unsigned redundancy,
+					       struct closure *cl)
 {
 	struct ec_stripe_head *h;
 	struct open_bucket *ob;
@@ -1421,14 +1421,13 @@ struct ec_stripe_head *bch2_ec_stripe_head_get(struct bch_fs *c,
 				bch2_ec_stripe_head_put(c, h);
 				h = NULL;
 				goto out;
-
 			}
-
 		}
 
-		if (new_stripe_alloc_buckets(c, h)) {
+		ret = new_stripe_alloc_buckets(c, h, cl);
+		if (ret) {
 			bch2_ec_stripe_head_put(c, h);
-			h = NULL;
+			h = ERR_PTR(-ret);
 			goto out;
 		}
 

fs/bcachefs/ec.h

@@ -146,8 +146,8 @@ void bch2_ec_bucket_cancel(struct bch_fs *, struct open_bucket *);
 int bch2_ec_stripe_new_alloc(struct bch_fs *, struct ec_stripe_head *);
 
 void bch2_ec_stripe_head_put(struct bch_fs *, struct ec_stripe_head *);
-struct ec_stripe_head *bch2_ec_stripe_head_get(struct bch_fs *, unsigned,
-					       unsigned, unsigned);
+struct ec_stripe_head *bch2_ec_stripe_head_get(struct bch_fs *,
+			unsigned, unsigned, unsigned, struct closure *);
 
 void bch2_stripes_heap_update(struct bch_fs *, struct stripe *, size_t);
 void bch2_stripes_heap_del(struct bch_fs *, struct stripe *, size_t);