> Hello, > > Thank you revisit this. But as far as my remember is correct, this issue is NOT > unaligned access issue. It's just get_user_pages(_fast) vs fork race issue. i.e. > DIRECT_IO w/ multi thread process should not use fork(). The problem is, fork (and its COW logic) assume new access makes cow break, But page table protection can't detect a DMA write. Therefore DIO may override shared page data. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>