bcachefs: Fix check_path() for snapshots

check_path() wasn't checking the snapshot ID when checking for directory
structure loops - so, snapshots would cause us to detect a loop that
wasn't actually a loop.

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

diff --git a/fs/bcachefs/fsck.c b/fs/bcachefs/fsck.c
index c99e1514fd4f7e394e6e76d977b6f631b3150183..d6f37b9e00fb1809a03acdc89c341856a628115d 100644 (file)
--- a/fs/bcachefs/fsck.c
+++ b/fs/bcachefs/fsck.c
@@ -1357,10 +1357,10 @@ static int check_dirent_target(struct btree_trans *trans,
                }
 
                if (fsck_err_on(!backpointer_exists, c,
-                               "inode %llu has wrong backpointer:\n"
+                               "inode %llu:%u has wrong backpointer:\n"
                                "got       %llu:%llu\n"
                                "should be %llu:%llu",
-                               target->bi_inum,
+                               target->bi_inum, target_snapshot,
                                target->bi_dir,
                                target->bi_dir_offset,
                                d.k->p.inode,
@@ -1730,10 +1730,23 @@ struct pathbuf {
 
        struct pathbuf_entry {
                u64     inum;
+               u32     snapshot;
        }               *entries;
 };
 
-static int path_down(struct pathbuf *p, u64 inum)
+static bool path_is_dup(struct pathbuf *p, u64 inum, u32 snapshot)
+{
+       struct pathbuf_entry *i;
+
+       for (i = p->entries; i < p->entries + p->nr; i++)
+               if (i->inum     == inum &&
+                   i->snapshot == snapshot)
+                       return true;
+
+       return false;
+}
+
+static int path_down(struct pathbuf *p, u64 inum, u32 snapshot)
 {
        if (p->nr == p->size) {
                size_t new_size = max_t(size_t, 256UL, p->size * 2);
@@ -1749,18 +1762,23 @@ static int path_down(struct pathbuf *p, u64 inum)
        };
 
        p->entries[p->nr++] = (struct pathbuf_entry) {
-               .inum = inum,
+               .inum           = inum,
+               .snapshot       = snapshot,
        };
        return 0;
 }
 
+/*
+ * Check that a given inode is reachable from the root:
+ *
+ * XXX: we should also be verifying that inodes are in the right subvolumes
+ */
 static int check_path(struct btree_trans *trans,
                      struct pathbuf *p,
                      struct bch_inode_unpacked *inode,
                      u32 snapshot)
 {
        struct bch_fs *c = trans->c;
-       size_t i;
        int ret = 0;
 
        snapshot = snapshot_t(c, snapshot)->equiv;
@@ -1768,17 +1786,19 @@ static int check_path(struct btree_trans *trans,
 
        while (!(inode->bi_inum == BCACHEFS_ROOT_INO &&
                 inode->bi_subvol == BCACHEFS_ROOT_SUBVOL)) {
+               u32 parent_snapshot = snapshot;
+
                if (inode->bi_parent_subvol) {
                        u64 inum;
 
                        ret = subvol_lookup(trans, inode->bi_parent_subvol,
-                                           &snapshot, &inum);
+                                           &parent_snapshot, &inum);
                        if (ret)
                                break;
                }
 
                ret = lockrestart_do(trans,
-                       inode_backpointer_exists(trans, inode, snapshot));
+                       inode_backpointer_exists(trans, inode, parent_snapshot));
                if (ret < 0)
                        break;
 
@@ -1797,17 +1817,31 @@ static int check_path(struct btree_trans *trans,
                if (!S_ISDIR(inode->bi_mode))
                        break;
 
-               ret = path_down(p, inode->bi_inum);
+               ret = path_down(p, inode->bi_inum, snapshot);
                if (ret) {
                        bch_err(c, "memory allocation failure");
                        return ret;
                }
 
-               for (i = 0; i < p->nr; i++) {
-                       if (inode->bi_dir != p->entries[i].inum)
-                               continue;
+               snapshot = parent_snapshot;
+
+               ret = lookup_inode(trans, inode->bi_dir, inode, &snapshot);
+               if (ret) {
+                       /* Should have been caught in dirents pass */
+                       bch_err(c, "error looking up parent directory: %i", ret);
+                       break;
+               }
+
+               if (path_is_dup(p, inode->bi_inum, snapshot)) {
+                       struct pathbuf_entry *i;
 
                        /* XXX print path */
+                       bch_err(c, "directory structure loop");
+
+                       for (i = p->entries; i < p->entries + p->nr; i++)
+                               pr_err("%llu:%u", i->inum, i->snapshot);
+                       pr_err("%llu:%u", inode->bi_inum, snapshot);
+
                        if (!fsck_err(c, "directory structure loop"))
                                return 0;
 
@@ -1819,14 +1853,6 @@ static int check_path(struct btree_trans *trans,
                        }
 
                        ret = reattach_inode(trans, inode, snapshot);
-                       break;
-               }
-
-               ret = lookup_inode(trans, inode->bi_dir, inode, &snapshot);
-               if (ret) {
-                       /* Should have been caught in dirents pass */
-                       bch_err(c, "error looking up parent directory: %i", ret);
-                       break;
                }
        }
 fsck_err: