On Mon, Dec 17, 2012 at 5:57 PM, Al Viro <viro@xxxxxxxxxxxxxxxxxx> wrote: > On Mon, Dec 17, 2012 at 05:10:21PM -0800, Andy Lutomirski wrote: >> I want to change inode->i_flags access to be atomic -- there are some >> locking oddities right now, I think, and I want to use a new inode >> flag to signal mtime updates from page_mkwrite. The problem is that >> i_flags is an unsigned int, and making it an unsigned long seems like >> a waste, but there aren't any u32 atomic bitops. > > ... and atomic accesses cost more. A lot more on some architectures. > FWIW, atomic_t *is* 32bit on 32bit architectures, which still doesn't > make it a good idea. Are atomic_set_mask and atomic_clear_mask as fast as set_bit and friends on all archs? In any case, i_flags looks like it's rarely written, so I find it a bit hard to believe that making it atomic would hurt. Isn't atomic_read equivalent to non-atomic reads everywhere? I want page_mkwrite to set a flag (without taking i_mutex) but *not* call file_update_time and then to have the writeback paths update the inode time. (This, along with stable pages, is the major cause of long sleeps in my application.) OTOH, maybe I should just use i_state and i_lock for this. --Andy -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
