Btrfs: fix wrong i_size when truncating a file to a larger size

Btrfsck report error 100 after the 83th case of xfstests was run, it means
the i_size of the file is wrong.

The reason of this bug is that:
Btrfs increased i_size of the file at the beginning, but it failed to expand
the file, and failed to update the i_size to the old size because there is no
enough space in the file system, so we found a wrong i_size.

This patch fixes this bug by updating the i_size just when we pass the file
expanding and get enough space to update i-node.

Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 12 insertions, 6 deletions

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index c5ccec23984c..4bbceb928aff 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -3370,6 +3370,8 @@ int btrfs_cont_expand(struct inode *inode, loff_t oldsize, loff_t size)
 
 static int btrfs_setsize(struct inode *inode, loff_t newsize)
 {
+        struct btrfs_root *root = BTRFS_I(inode)->root;
+        struct btrfs_trans_handle *trans;
         loff_t oldsize = i_size_read(inode);
         int ret;
 
@@ -3377,16 +3379,20 @@ static int btrfs_setsize(struct inode *inode, loff_t newsize)
                 return 0;
 
         if (newsize > oldsize) {
-                i_size_write(inode, newsize);
-                btrfs_ordered_update_i_size(inode, i_size_read(inode), NULL);
                 truncate_pagecache(inode, oldsize, newsize);
                 ret = btrfs_cont_expand(inode, oldsize, newsize);
-                if (ret) {
-                        btrfs_setsize(inode, oldsize);
+                if (ret)
                         return ret;
-                }
 
-                mark_inode_dirty(inode);
+                trans = btrfs_start_transaction(root, 1);
+                if (IS_ERR(trans))
+                        return PTR_ERR(trans);
+
+                i_size_write(inode, newsize);
+                btrfs_ordered_update_i_size(inode, i_size_read(inode), NULL);
+                ret = btrfs_update_inode(trans, root, inode);
+
+                btrfs_end_transaction_throttle(trans, root);
         } else {
 
                 /*