On Fri 18-05-12 20:12:10, Dave Chinner wrote: > On Fri, May 18, 2012 at 01:28:29AM +0200, Jan Kara wrote: > > On Thu 17-05-12 17:43:08, Dave Chinner wrote: > > > On Wed, May 16, 2012 at 03:04:45PM +0200, Jan Kara wrote: > > > > On Wed 16-05-12 12:14:23, Dave Chinner wrote: > > > IIRC, it's a rare case (that I consider insane, BTW): read from a > > > file with into a buffer that is a mmap()d region of the same file > > > that has not been faulted in yet..... > > With punch hole, the race is less insane - just punching hole in the area > > which is accessed via mmap could race in a bad way AFAICS. > > Seems the simple answer to me is to prevent page faults while hole > punching, then.... Yes, that's what I was suggesting in the beginning :) And I was asking whether people are OK with another lock in the page fault path (in particular in ->page_mkwrite) or whether someone has a better idea (e.g. taking mmap_sem in the hole punching path seems possible but I'm not sure whether that would be considered acceptable abuse). Honza -- Jan Kara <jack@xxxxxxx> SUSE Labs, CR -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
