On Tue, Oct 6, 2015 at 12:33 AM, Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx> wrote: > > Did you mean that as a cleanup, or to fix the regression? Purely as a cleanup to try to avoid the (already existing) special case in at least ext4 - and possibly others. So that patch was meant just for discussion - it's not really fixing any existing bugs, and I didn't actually keep it live in my tree. I'm planning on just doing the revert for now, but I'll wait a bit to see how this thread pans out first. > Since the page isn't faulted in yet, iov_iter_copy_from_user_atomic() > had already set copied=0 Not necessarily. For your case that only does one-byte writes, yes. But in the generic case you may well have a page-crossing source area in user space, and get a partial success from the user copy. It's that partial success case (when the rest of the missing data isn't necessarily already up-to-date) that I'd like to have low-level filesystems not have to worry about. Linus -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html