[PATCH 1/5] nilfs2: treat missing sufile header block as metadata corruption

[Ryusuke Konishi <konishi.ryusuke@gmail.com>]

The sufile, a metadata file that holds metadata for segment management,
has statistical information in its first block, but if reading this
block fails, it receives the internal code -ENOENT and returns it
unchanged to the callers.

To prevent this -ENOENT from being propagated to system calls, if
reading the header block fails, return -EIO (or -EINVAL depending on
the context) instead.

Signed-off-by: Ryusuke Konishi <konishi.ryusuke@gmail.com>
---
 fs/nilfs2/sufile.c | 23 ++++++++++++++++++-----
 1 file changed, 18 insertions(+), 5 deletions(-)

diff --git a/fs/nilfs2/sufile.c b/fs/nilfs2/sufile.c
index 7bfc0860acee..f071eba48163 100644
--- a/fs/nilfs2/sufile.c
+++ b/fs/nilfs2/sufile.c
@@ -79,10 +79,17 @@ nilfs_sufile_block_get_segment_usage(const struct inode *sufile, __u64 segnum,
 		NILFS_MDT(sufile)->mi_entry_size;
 }
 
-static inline int nilfs_sufile_get_header_block(struct inode *sufile,
-						struct buffer_head **bhp)
+static int nilfs_sufile_get_header_block(struct inode *sufile,
+					 struct buffer_head **bhp)
 {
-	return nilfs_mdt_get_block(sufile, 0, 0, NULL, bhp);
+	int err = nilfs_mdt_get_block(sufile, 0, 0, NULL, bhp);
+
+	if (unlikely(err == -ENOENT)) {
+		nilfs_error(sufile->i_sb,
+			    "missing header block in segment usage metadata");
+		err = -EIO;
+	}
+	return err;
 }
 
 static inline int
@@ -1237,9 +1244,15 @@ int nilfs_sufile_read(struct super_block *sb, size_t susize,
 	if (err)
 		goto failed;
 
-	err = nilfs_sufile_get_header_block(sufile, &header_bh);
-	if (err)
+	err = nilfs_mdt_get_block(sufile, 0, 0, NULL, &header_bh);
+	if (unlikely(err)) {
+		if (err == -ENOENT) {
+			nilfs_err(sb,
+				  "missing header block in segment usage metadata");
+			err = -EINVAL;
+		}
 		goto failed;
+	}
 
 	sui = NILFS_SUI(sufile);
 	kaddr = kmap_local_page(header_bh->b_page);
-- 
2.34.1