On Tue, Jun 22, 2021 at 04:20:40PM +0100, David Howells wrote: > and wondering if the iov_iter_fault_in_readable() is actually effective. Yes, > it can make sure that the page we're intending to modify is dragged into the > pagecache and marked uptodate so that it can be read from, but is it possible > for the page to then get reclaimed before we get to > iov_iter_copy_from_user_atomic()? a_ops->write_begin() could potentially take > a long time, say if it has to go and get a lock/lease from a server. Yes, it is. So what? We'll just retry. You *can't* take faults while holding some pages locked; not without shitloads of deadlocks.
