ext4: Use a fake block number for delayed new buffer_head

(cherry picked from commit 33b9817e2ae097c7b8d256e3510ac6c54fc6d9d0)

Use a very large unsigned number (~0xffff) as as the fake block number
for the delayed new buffer. The VFS should never try to write out this
number, but if it does, this will make it obvious.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 03be1225944cb092758f507adb0e3ad7d5558607..57923cc150c666d0cb7a86b29a037c9f5e23b85b 100644 (file)
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -2220,6 +2220,10 @@ static int ext4_da_get_block_prep(struct inode *inode, sector_t iblock,
                                  struct buffer_head *bh_result, int create)
 {
        int ret = 0;
+       sector_t invalid_block = ~((sector_t) 0xffff);
+
+       if (invalid_block < ext4_blocks_count(EXT4_SB(inode->i_sb)->s_es))
+               invalid_block = ~0;
 
        BUG_ON(create == 0);
        BUG_ON(bh_result->b_size != inode->i_sb->s_blocksize);
@@ -2241,7 +2245,7 @@ static int ext4_da_get_block_prep(struct inode *inode, sector_t iblock,
                        /* not enough space to reserve */
                        return ret;
 
-               map_bh(bh_result, inode->i_sb, 0);
+               map_bh(bh_result, inode->i_sb, invalid_block);
                set_buffer_new(bh_result);
                set_buffer_delay(bh_result);
        } else if (ret > 0) {