From 962ad1a76669443126c6531352380f56d6e5d7d2 Mon Sep 17 00:00:00 2001
From: Kent Overstreet <kent.overstreet@gmail.com>
Date: Thu, 23 Jun 2022 18:26:01 -0400
Subject: [PATCH] bcachefs: Don't BUG_ON() inode link count underflow

This switches that assertion to a bch2_trans_inconsistent() call, as it
should be.

Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
---
 fs/bcachefs/fs-common.c |  8 +++++---
 fs/bcachefs/inode.c     | 33 +++++++++++++++++++++++++++++++++
 fs/bcachefs/inode.h     | 20 +++-----------------
 3 files changed, 41 insertions(+), 20 deletions(-)

diff --git a/fs/bcachefs/fs-common.c b/fs/bcachefs/fs-common.c
index d543480be111..53ffc684223c 100644
--- a/fs/bcachefs/fs-common.c
+++ b/fs/bcachefs/fs-common.c
@@ -204,7 +204,9 @@ int bch2_link_trans(struct btree_trans *trans,
 		goto err;
 
 	inode_u->bi_ctime = now;
-	bch2_inode_nlink_inc(inode_u);
+	ret = bch2_inode_nlink_inc(inode_u);
+	if (ret)
+		return ret;
 
 	ret = bch2_inode_peek(trans, &dir_iter, dir_u, dir, BTREE_ITER_INTENT);
 	if (ret)
@@ -297,7 +299,7 @@ int bch2_unlink_trans(struct btree_trans *trans,
 		if (ret)
 			goto err;
 	} else {
-		bch2_inode_nlink_dec(inode_u);
+		bch2_inode_nlink_dec(trans, inode_u);
 	}
 
 	if (inode_u->bi_dir		== dirent_iter.pos.inode &&
@@ -462,7 +464,7 @@ int bch2_rename_trans(struct btree_trans *trans,
 	}
 
 	if (mode == BCH_RENAME_OVERWRITE)
-		bch2_inode_nlink_dec(dst_inode_u);
+		bch2_inode_nlink_dec(trans, dst_inode_u);
 
 	src_dir_u->bi_mtime		= now;
 	src_dir_u->bi_ctime		= now;
diff --git a/fs/bcachefs/inode.c b/fs/bcachefs/inode.c
index 6c0547151d50..5de66d62028b 100644
--- a/fs/bcachefs/inode.c
+++ b/fs/bcachefs/inode.c
@@ -716,3 +716,36 @@ int bch2_inode_find_by_inum(struct bch_fs *c, subvol_inum inum,
 	return bch2_trans_do(c, NULL, NULL, 0,
 		bch2_inode_find_by_inum_trans(&trans, inum, inode));
 }
+
+int bch2_inode_nlink_inc(struct bch_inode_unpacked *bi)
+{
+	if (bi->bi_flags & BCH_INODE_UNLINKED)
+		bi->bi_flags &= ~BCH_INODE_UNLINKED;
+	else {
+		if (bi->bi_nlink == U32_MAX)
+			return -EINVAL;
+
+		bi->bi_nlink++;
+	}
+
+	return 0;
+}
+
+void bch2_inode_nlink_dec(struct btree_trans *trans, struct bch_inode_unpacked *bi)
+{
+	if (bi->bi_nlink && (bi->bi_flags & BCH_INODE_UNLINKED)) {
+		bch2_trans_inconsistent(trans, "inode %llu unlinked but link count nonzero",
+					bi->bi_inum);
+		return;
+	}
+
+	if (bi->bi_flags & BCH_INODE_UNLINKED) {
+		bch2_trans_inconsistent(trans, "inode %llu link count underflow", bi->bi_inum);
+		return;
+	}
+
+	if (bi->bi_nlink)
+		bi->bi_nlink--;
+	else
+		bi->bi_flags |= BCH_INODE_UNLINKED;
+}
diff --git a/fs/bcachefs/inode.h b/fs/bcachefs/inode.h
index 9442600a7440..2ac2fc10513b 100644
--- a/fs/bcachefs/inode.h
+++ b/fs/bcachefs/inode.h
@@ -164,23 +164,6 @@ static inline unsigned nlink_bias(umode_t mode)
 	return S_ISDIR(mode) ? 2 : 1;
 }
 
-static inline void bch2_inode_nlink_inc(struct bch_inode_unpacked *bi)
-{
-	if (bi->bi_flags & BCH_INODE_UNLINKED)
-		bi->bi_flags &= ~BCH_INODE_UNLINKED;
-	else
-		bi->bi_nlink++;
-}
-
-static inline void bch2_inode_nlink_dec(struct bch_inode_unpacked *bi)
-{
-	BUG_ON(bi->bi_flags & BCH_INODE_UNLINKED);
-	if (bi->bi_nlink)
-		bi->bi_nlink--;
-	else
-		bi->bi_flags |= BCH_INODE_UNLINKED;
-}
-
 static inline unsigned bch2_inode_nlink_get(struct bch_inode_unpacked *bi)
 {
 	return bi->bi_flags & BCH_INODE_UNLINKED
@@ -200,4 +183,7 @@ static inline void bch2_inode_nlink_set(struct bch_inode_unpacked *bi,
 	}
 }
 
+int bch2_inode_nlink_inc(struct bch_inode_unpacked *);
+void bch2_inode_nlink_dec(struct btree_trans *, struct bch_inode_unpacked *);
+
 #endif /* _BCACHEFS_INODE_H */