f2fs: move f2fs_balance_fs from truncate to punch_hole

Move the f2fs_balance_fs out of the truncate_hole function and only
perform that in punch_hole use case.  The commit:

  ed60b1644e7f7e5dd67d21caf7e4425dff05dad0

intended to do this but moved it into truncate_hole to cover more
cases.  However, a deadlock scenario is possible when deleting an inode
entry under specific conditions:

 f2fs_delete_entry()
     mutex_lock_op(sbi, DENTRY_OPS);
     truncate_hole()
         f2fs_balance_fs()
             mutex_lock(&sbi->gc_mutex);
             f2fs_gc()
                 write_checkpoint()
                     block_operations()
                         mutex_lock_op(sbi, DENTRY_OPS);

Lets move it into the punch_hole case to cover the original intent of
avoiding it during fallocate's expand_inode_data case.

Change-Id: I29f8ea1056b0b88b70ba8652d901b6e8431bb27e
Signed-off-by: NJason Hrycay <jason.hrycay@motorola.com>
Signed-off-by: NJaegeuk Kim <jaegeuk.kim@samsung.com>

fs/f2fs/file.c

@@ -390,8 +390,6 @@ int truncate_hole(struct inode *inode, pgoff_t pg_start, pgoff_t pg_end)
 		struct dnode_of_data dn;
 		struct f2fs_sb_info *sbi = F2FS_SB(inode->i_sb);
 
-		f2fs_balance_fs(sbi);
-
 		mutex_lock_op(sbi, DATA_TRUNC);
 		set_new_dnode(&dn, inode, NULL, NULL, 0);
 		err = get_dnode_of_data(&dn, index, LOOKUP_NODE);
@@ -435,6 +433,9 @@ static int punch_hole(struct inode *inode, loff_t offset, loff_t len, int mode)
 		if (pg_start < pg_end) {
 			struct address_space *mapping = inode->i_mapping;
 			loff_t blk_start, blk_end;
+			struct f2fs_sb_info *sbi = F2FS_SB(inode->i_sb);
+
+			f2fs_balance_fs(sbi);
 
 			blk_start = pg_start << PAGE_CACHE_SHIFT;
 			blk_end = pg_end << PAGE_CACHE_SHIFT;