[PATCH] ext4: Fix to read empty directory blocks correctly in 64k blocksize filesystems

[Wei Yongjun <yjwei@cn.fujitsu.com>]

The rec_len field in the directory entry is 16 bits, so if the
filesystem is completely empty, rec_len of 0 is used to designate
65536, for the case where the directory entry takes the entire 64k
block.

But if empty directory block is read, error message will be output
by current kernel. You can do the following commands to reproduct it.

> mkfs.ext4 -b $(( 64 * 1024 )) /dev/sda1
> mount -t ext4 /dev/sda1 /mnt
> cd /mnt/lost+found
> ll
> tail /var/log/messages
EXT4-fs error (device sdc1): ext4_readdir: bad entry in \
directory #11: rec_len is smaller than minimal - offset=0, \
inode=0, rec_len=0, name_len=0

This patch fix to treat rec_len of 0 as 65536, like what e2fsprogs do.

Signed-off-by: Wei Yongjun <yjwei@cn.fujitsu.com>
---
 fs/ext4/ext4.h |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index aafc9eb..b0c87dc 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -868,7 +868,7 @@ static inline unsigned ext4_rec_len_from_disk(__le16 dlen)
 {
 	unsigned len = le16_to_cpu(dlen);
 
-	if (len == EXT4_MAX_REC_LEN)
+	if (len == EXT4_MAX_REC_LEN || len == 0)
 		return 1 << 16;
 	return len;
 }
-- 
1.5.3.8