[PATCH 1/3] bcachefs: return -EMLINK instead of -EINVAL when hard link count exceeds limit

[Youling Tang <youling.tang@linux.dev>]

From: Youling Tang <tangyouling@kylinos.cn>

Currently bcachefs returns -EINVAL when the hard link count reaches
U32_MAX. However, -EINVAL is a generic invalid argument error that
doesn't accurately convey the specific "too many links" condition.

This patch changes the error return code from -EINVAL to -EMLINK
when the hard link count limit is exceeded, providing more precise
error information to userspace and making it consistent with other
filesystems' behavior.

Signed-off-by: Youling Tang <tangyouling@kylinos.cn>
---
 fs/bcachefs/errcode.h | 1 +
 fs/bcachefs/inode.c   | 2 +-
 2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/bcachefs/errcode.h b/fs/bcachefs/errcode.h
index acc3b7b67704..b22a694ec750 100644
--- a/fs/bcachefs/errcode.h
+++ b/fs/bcachefs/errcode.h
@@ -215,6 +215,7 @@
 	x(EINVAL,			varint_decode_error)			\
 	x(EINVAL,			erasure_coding_found_btree_node)	\
 	x(EINVAL,			option_negative)			\
+	x(EMLINK,			too_many_links)				\
 	x(EOPNOTSUPP,			may_not_use_incompat_feature)		\
 	x(EROFS,			erofs_trans_commit)			\
 	x(EROFS,			erofs_no_writes)			\
diff --git a/fs/bcachefs/inode.c b/fs/bcachefs/inode.c
index ef4cc7395b86..5765144b4d65 100644
--- a/fs/bcachefs/inode.c
+++ b/fs/bcachefs/inode.c
@@ -1193,7 +1193,7 @@ int bch2_inode_nlink_inc(struct bch_inode_unpacked *bi)
 		bi->bi_flags &= ~BCH_INODE_unlinked;
 	else {
 		if (bi->bi_nlink == U32_MAX)
-			return -EINVAL;
+			return -BCH_ERR_too_many_links;
 
 		bi->bi_nlink++;
 	}
-- 
2.43.0