bcachefs: Fix disk accounting attempting to mark invalid replicas entry

This fixes the following bug, where a disk accounting key has an invalid
replicas entry, and we attempt to add it to the superblock:

bcachefs (3c0860e8-07ca-4276-8954-11c1774be868): starting version 1.12: rebalance_work_acct_fix opts=metadata_replicas=2,data_replicas=2,foreground_target=ssd,background_target=hdd,nopromote_whole_extents,verbose,fsck,fix_errors=yes
bcachefs (3c0860e8-07ca-4276-8954-11c1774be868): recovering from clean shutdown, journal seq 15211644
bcachefs (3c0860e8-07ca-4276-8954-11c1774be868): accounting_read...
accounting not marked in superblock replicas
  replicas cached: 1/1 [0], fixing
bcachefs (3c0860e8-07ca-4276-8954-11c1774be868): sb invalid before write: Invalid superblock section replicas_v0: invalid device 0 in entry cached: 1/1 [0]
replicas_v0 (size 88):
user: 2 [3 5] user: 2 [1 4] cached: 1 [2] btree: 2 [1 2] user: 2 [2 5] cached: 1 [0] cached: 1 [4] journal: 2 [1 5] user: 2 [1 2] user: 2 [2 3] user: 2 [3 4] user: 2 [4 5] cached: 1 [1] cached: 1 [3] cached: 1 [5] journal: 2 [1 2] journal: 2 [2 5] btree: 2 [2 5] user: 2 [1 3] user: 2 [1 5] user: 2 [2 4]

bcachefs (3c0860e8-07ca-4276-8954-11c1774be868): inconsistency detected - emergency read only at journal seq 15211644
accounting not marked in superblock replicas
  replicas user: 1/1 [3], fixing
bcachefs (3c0860e8-07ca-4276-8954-11c1774be868): sb invalid before write: Invalid superblock section replicas_v0: invalid device 0 in entry cached: 1/1 [0]
replicas_v0 (size 96):
user: 2 [3 5] user: 2 [1 3] cached: 1 [2] btree: 2 [1 2] user: 2 [2 4] cached: 1 [0] cached: 1 [4] journal: 2 [1 5] user: 1 [3] user: 2 [1 5] user: 2 [3 4] user: 2 [4 5] cached: 1 [1] cached: 1 [3] cached: 1 [5] journal: 2 [1 2] journal: 2 [2 5] btree: 2 [2 5] user: 2 [1 2] user: 2 [1 4] user: 2 [2 3] user: 2 [2 5]

accounting not marked in superblock replicas
  replicas user: 1/2 [3 7], fixing
bcachefs (3c0860e8-07ca-4276-8954-11c1774be868): sb invalid before write: Invalid superblock section replicas_v0: invalid device 7 in entry user: 1/2 [3 7]
replicas_v0 (size 96):
user: 2 [3 7] user: 2 [1 3] cached: 1 [2] btree: 2 [1 2] user: 2 [2 4] cached: 1 [0] cached: 1 [4] journal: 2 [1 5] user: 1 [3] user: 2 [1 5] user: 2 [3 4] user: 2 [4 5] cached: 1 [1] cached: 1 [3] cached: 1 [5] journal: 2 [1 2] journal: 2 [2 5] btree: 2 [2 5] user: 2 [1 2] user: 2 [1 4] user: 2 [2 3] user: 2 [2 5] user: 2 [3 5]

 done
bcachefs (3c0860e8-07ca-4276-8954-11c1774be868): alloc_read... done
bcachefs (3c0860e8-07ca-4276-8954-11c1774be868): stripes_read... done
bcachefs (3c0860e8-07ca-4276-8954-11c1774be868): snapshots_read... done
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/disk_accounting.c

@@ -671,10 +671,16 @@ int bch2_accounting_read(struct bch_fs *c)
 			continue;
 
 		struct bch_replicas_padded r;
-
 		if (!accounting_to_replicas(&r.e, acc->k.data[i].pos))
 			continue;
 
+		/*
+		 * If the replicas entry is invalid it'll get cleaned up by
+		 * check_allocations:
+		 */
+		if (bch2_replicas_entry_validate(&r.e, c, &buf))
+			continue;
+
 		struct disk_accounting_pos k;
 		bpos_to_disk_accounting_pos(&k, acc->k.data[i].pos);
 
@@ -683,8 +689,17 @@ int bch2_accounting_read(struct bch_fs *c)
 				"accounting not marked in superblock replicas\n  %s",
 				(printbuf_reset(&buf),
 				 bch2_accounting_key_to_text(&buf, &k),
-				 buf.buf)))
-			ret = bch2_accounting_update_sb_one(c, acc->k.data[i].pos);
+				 buf.buf))) {
+			/*
+			 * We're not RW yet and still single threaded, dropping
+			 * and retaking lock is ok:
+			 */
+			percpu_up_read(&c->mark_lock);
+			ret = bch2_mark_replicas(c, &r.e);
+			if (ret)
+				goto fsck_err;
+			percpu_down_read(&c->mark_lock);
+		}
 	}
 
 	preempt_disable();