On Fri, Dec 14, 2012 at 6:49 AM, Al Viro <viro@xxxxxxxxxxxxxxxxxx> wrote: > On Fri, Dec 14, 2012 at 03:14:50AM -0800, Andy Lutomirski wrote: > >> > Wait a minute. get_user_pages() relies on ->mmap_sem being held. Unless >> > I'm seriously misreading your patch it removes that protection. And yes, >> > I'm aware of execve-related exception; it's in special circumstances - >> > bprm->mm is guaranteed to be not shared (and we need to rearchitect that >> > area anyway, but that's a separate story). >> >> Unless I completely screwed up the patch, ->mmap_sem is still held for >> read (it's downgraded from write). It's just not held for write >> anymore. > > Huh? I'm talking about the call of get_user_pages() in aio_setup_ring(). > With your patch it's done completely outside of ->mmap_sem, isn't it? Oh, /that/ call to get_user_pages. That would qualify as screwing up... Since dropping and reacquiring mmap_sem there is probably a bad idea there, I'll rework this and post a v2. --Andy -- 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>