bcachefs: bch2_lookup() gives better error message on inode not found

When a dirent points to a missing inode, we really should print out the
dirent.

This requires quite a bit of refactoring, but there's some other
benefits: we now do the entire looup (dirent and inode) in a single
btree transaction, and copy to the VFS inode with btree locks still
held, like the create path.

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

diff --git a/fs/bcachefs/fs.c b/fs/bcachefs/fs.c
index bcc1436..093f540 100644 (file)
--- a/fs/bcachefs/fs.c
+++ b/fs/bcachefs/fs.c
@@ -365,23 +365,78 @@ err_trans:
 
 /* methods */
 
+static struct bch_inode_info *bch2_lookup_trans(struct btree_trans *trans,
+                       subvol_inum dir, struct bch_hash_info *dir_hash_info,
+                       const struct qstr *name)
+{
+       struct bch_fs *c = trans->c;
+       struct btree_iter dirent_iter = {};
+       subvol_inum inum = {};
+
+       int ret = bch2_hash_lookup(trans, &dirent_iter, bch2_dirent_hash_desc,
+                                  dir_hash_info, dir, name, 0);
+       if (ret)
+               return ERR_PTR(ret);
+
+       struct bkey_s_c k = bch2_btree_iter_peek_slot(&dirent_iter);
+       ret = bkey_err(k);
+       if (ret)
+               goto err;
+
+       ret = bch2_dirent_read_target(trans, dir, bkey_s_c_to_dirent(k), &inum);
+       if (ret > 0)
+               ret = -ENOENT;
+       if (ret)
+               goto err;
+
+       struct bch_inode_info *inode =
+               to_bch_ei(ilookup5_nowait(c->vfs_sb,
+                                         bch2_inode_hash(inum),
+                                         bch2_iget5_test,
+                                         &inum));
+       if (inode)
+               goto out;
+
+       struct bch_subvolume subvol;
+       struct bch_inode_unpacked inode_u;
+       ret =   bch2_subvolume_get(trans, inum.subvol, true, 0, &subvol) ?:
+               bch2_inode_find_by_inum_nowarn_trans(trans, inum, &inode_u) ?:
+               PTR_ERR_OR_ZERO(inode = bch2_new_inode(trans));
+       if (bch2_err_matches(ret, ENOENT)) {
+               struct printbuf buf = PRINTBUF;
+
+               bch2_bkey_val_to_text(&buf, c, k);
+               bch_err(c, "%s points to missing inode", buf.buf);
+               printbuf_exit(&buf);
+       }
+       if (ret)
+               goto err;
+
+       bch2_vfs_inode_init(trans, inum, inode, &inode_u, &subvol);
+       inode = bch2_inode_insert(c, inode);
+out:
+       bch2_trans_iter_exit(trans, &dirent_iter);
+       return inode;
+err:
+       inode = ERR_PTR(ret);
+       goto out;
+}
+
 static struct dentry *bch2_lookup(struct inode *vdir, struct dentry *dentry,
                                  unsigned int flags)
 {
        struct bch_fs *c = vdir->i_sb->s_fs_info;
        struct bch_inode_info *dir = to_bch_ei(vdir);
        struct bch_hash_info hash = bch2_hash_info_init(c, &dir->ei_inode);
-       struct inode *vinode = NULL;
-       subvol_inum inum = { .subvol = 1 };
-       int ret;
-
-       ret = bch2_dirent_lookup(c, inode_inum(dir), &hash,
-                                &dentry->d_name, &inum);
 
-       if (!ret)
-               vinode = bch2_vfs_inode_get(c, inum);
+       struct bch_inode_info *inode;
+       bch2_trans_do(c, NULL, NULL, 0,
+               PTR_ERR_OR_ZERO(inode = bch2_lookup_trans(trans, inode_inum(dir),
+                                                         &hash, &dentry->d_name)));
+       if (IS_ERR(inode))
+               inode = NULL;
 
-       return d_splice_alias(vinode, dentry);
+       return d_splice_alias(&inode->v, dentry);
 }
 
 static int bch2_mknod(struct mnt_idmap *idmap,