On Wed, Oct 11, 2017 at 6:28 PM, Dan Williams <dan.j.williams@xxxxxxxxx> wrote: > On Wed, Oct 11, 2017 at 6:21 PM, Al Viro <viro@xxxxxxxxxxxxxxxxxx> wrote: >> On Wed, Oct 11, 2017 at 05:47:18PM -0700, Dan Williams wrote: >>> The MAP_DIRECT mechanism for mmap intends to use a file lease to prevent >>> block map changes while the file is mapped. It requires the fd to setup >>> an fasync_struct for signalling lease break events to the lease holder. >> >> *UGH* >> >> That looks like one hell of a bad API. You are not even guaranteed that >> descriptor will remain be still open by the time you pass it down to your >> helper, nevermind the moment when event actually happens... > > What am I missing, fcntl(F_SETLEASE) seems to follow a similar pattern? Ugh, so I think the difference with F_SETLEASE is that the lease ends when the fd is closed. In the mmap case the lease follows the lifetime of the vma. I'll rethink this interface...
