ocfs2: take ip_alloc_sem during entire truncate

Use of the alloc sem during truncate was too narrow - we want to protect
the i_size change and page truncation against mmap now.

Signed-off-by: Mark Fasheh <mark.fasheh@oracle.com>

fs/ocfs2/alloc.c

@@ -3631,8 +3631,6 @@ int ocfs2_commit_truncate(struct ocfs2_super *osb,
 
 	mlog_entry_void();
 
-	down_write(&OCFS2_I(inode)->ip_alloc_sem);
-
 	new_highest_cpos = ocfs2_clusters_for_bytes(osb->sb,
 						     i_size_read(inode));
 
@@ -3754,7 +3752,6 @@ start:
 	goto start;
 
 bail:
-	up_write(&OCFS2_I(inode)->ip_alloc_sem);
 
 	ocfs2_schedule_truncate_log_flush(osb, 1);