f2fs: fix incorrect mapping for bmap

The test step is like below:
1. touch file
2. truncate -s $((1024*1024)) file
3. fallocate -o 0 -l $((1024*1024)) file
4. fibmap.f2fs file

Our result of fibmap.f2fs showed below is not correct:

file_pos   start_blk     end_blk        blks
       0    -937166132    -937166132           1
    4096    -937166132    -937166132           1
    8192    -937166132    -937166132           1
   12288    -937166132    -937166132           1
   16384    -937166132    -937166132           1
   20480    -937166132    -937166132           1
...
 1040384    -937166132    -937166132           1
 1044480    -937166132    -937166132           1

This is because f2fs_map_blocks will return with no error when meeting
a hole or preallocated block, the caller __get_data_block will map the
uninitialized variable value to bh->b_blocknr.

Unfortunately generic_block_bmap will neither check the return value of
get_data() nor check mapping info of buffer_head, result in returning
the random block address.

After fixing the issue, our result shows correctly:

file_pos   start_blk     end_blk        blks
       0           0           0         256

Signed-off-by: Chao Yu <chao2.yu@samsung.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

1 files changed, 6 insertions, 0 deletions

diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index 00591f7..51dfa8f 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -375,6 +375,12 @@ struct f2fs_map_blocks {
 	unsigned int m_flags;
 };
 
+/* for flag in get_data_block */
+#define F2FS_GET_BLOCK_READ		0
+#define F2FS_GET_BLOCK_DIO		1
+#define F2FS_GET_BLOCK_FIEMAP		2
+#define F2FS_GET_BLOCK_BMAP		3
+
 /*
  * i_advise uses FADVISE_XXX_BIT. We can add additional hints later.
  */