On Tue, Feb 28, 2017 at 08:28:08PM +0000, Lorenzo Stoakes wrote: > On 28 February 2017 at 19:35, Al Viro <viro@xxxxxxxxxxxxxxxxxx> wrote: > > On Tue, Feb 28, 2017 at 10:01:10AM +0100, Daniel Vetter wrote: > > > >> > + ret = get_user_pages_unlocked((unsigned long)xfer->mem_addr, > >> > + vsg->num_pages, vsg->pages, > >> > + (vsg->direction == DMA_FROM_DEVICE) ? FOLL_WRITE : 0); > > > > Umm... Why not > > ret = get_user_pages_fast((unsigned long)xfer->mem_addr, > > vsg->num_pages, > > vsg->direction == DMA_FROM_DEVICE, > > vsg->pages); > > > > IOW, do you really need a warranty that ->mmap_sem will be grabbed and > > released? > > Daniel will be better placed to answer in this specific case, but more > generally is there any reason why we can't just use > get_user_pages_fast() in all such cases? These patches were simply a > mechanical/cautious replacement for code that is more or less exactly > equivalent but if this would make sense perhaps it'd be worth using > gup_fast() where possible? I have no idea. drm/via is unmaintained, it's a dri1 racy driver with problems probably everywhere, and I'm not sure we even have someone left who cares (there's an out-of-tree kms conversion of via, but it's stuck since years). In short, it's the drm dungeons and the only reason I merge patches is to give people an easy target for test driving the patch submission process to dri-devel. And to avoid drm being a blocker for tree-wide refactorings. Otherwise 0 reasons to change anything here. -Daniel -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch -- 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/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
