On Wed 08-12-21 15:01:24, Matthew Wilcox wrote: > On Tue, Dec 07, 2021 at 03:08:19PM -0800, Suren Baghdasaryan wrote: > > > > /** > > > > * @close: Called when the VMA is being removed from the MM. > > > > * Context: Caller holds mmap_lock. > > > > BTW, is the caller always required to hold mmap_lock for write or it > > *might* hold it? > > __do_munmap() might hold it for read, thanks to: > > if (downgrade) > mmap_write_downgrade(mm); > > Should probably say: > > * Context: User context. May sleep. Caller holds mmap_lock. > > I don't think we should burden the implementor of the vm_ops with the > knowledge that the VM chooses to not hold the mmap_lock under certain > circumstances when it doesn't matter whether it's holding the mmap_lock > or not. If we document it like that some code might depend on that lock to be held. I think we only want to document that the holder itself is not allowed to take mmap sem or a depending lock. -- Michal Hocko SUSE Labs
