Btrfs: fix typo in fallocate to make it honor actual size

There is a typo in __btrfs_prealloc_file_range() where we set the i_size to
actual_len/cur_offset, and then just set it to cur_offset again, and do the same
with btrfs_ordered_update_i_size().  This fixes it back to keeping i_size in a
local variable and then updating i_size properly.  Tested this with

xfs_io -F -f -c "falloc 0 1" -c "pwrite 0 1" foo

stat'ing foo gives us a size of 1 instead of 4096 like it was.  Thanks,

Signed-off-by: Josef Bacik <josef@redhat.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 5 insertions, 4 deletions

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 37cc1776a5d7..0058fb3c2561 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -7002,6 +7002,7 @@ static int __btrfs_prealloc_file_range(struct inode *inode, int mode,
         struct btrfs_root *root = BTRFS_I(inode)->root;
         struct btrfs_key ins;
         u64 cur_offset = start;
+        u64 i_size;
         int ret = 0;
         bool own_trans = true;
 
@@ -7043,11 +7044,11 @@ static int __btrfs_prealloc_file_range(struct inode *inode, int mode,
                     (actual_len > inode->i_size) &&
                     (cur_offset > inode->i_size)) {
                         if (cur_offset > actual_len)
-                                i_size_write(inode, actual_len);
+                                i_size = actual_len;
                         else
-                                i_size_write(inode, cur_offset);
-                        i_size_write(inode, cur_offset);
-                        btrfs_ordered_update_i_size(inode, cur_offset, NULL);
+                                i_size = cur_offset;
+                        i_size_write(inode, i_size);
+                        btrfs_ordered_update_i_size(inode, i_size, NULL);
                 }
 
                 ret = btrfs_update_inode(trans, root, inode);