On Fri, Aug 25, 2023 at 03:44:57AM +0100, Al Viro wrote: > That got me curious about the ->bd_openers - do we need it atomic? > Most of the users (and all places that do modifications) are > under ->open_mutex; the only exceptions are > * early sync logics in blkdev_put(); it's explicitly racy - > see the comment there. > * callers of disk_openers() in loop and nbd (the ones in > zram are under ->open_mutex). There's driver-private exclusion > around those, but in any case - READ_ONCE() is no worse than > atomic_read() in those cases. > > Is there something subtle I'm missing here? No. When I had to add unlocked readers I did the READ_ONCE initially, but reviewers though the atomic_t would be better. I didn't really feel like arguing so went with this version.
