On Tue, Aug 1, 2017 at 4:26 AM, Jan Kara <jack@xxxxxxx> wrote: > On Tue 01-08-17 04:02:41, Christoph Hellwig wrote: >> On Fri, Jul 28, 2017 at 11:38:21AM +0200, Jan Kara wrote: >> > Well, you are right I can make the implementation work with struct file >> > flag as well - let's call it O_DAXDSYNC. However there are filesystem >> > operations where you may need to answer question: Is there any fd with >> > O_DAXDSYNC open against this inode (for operations that change file offset >> > -> block mapping)? And in that case inode flag is straightforward while >> > file flag is a bit awkward (you need to implement counter of fd's with that >> > flag in the inode). >> >> We can still keep and inode flag as the internal implementation >> detail. As mentioned earlier the right flag to control behavior >> of a mapping is an mmap flag. And the initial naive implementation >> would simply mark the inode as sync once the first MAP_SYNC open happens >> on it. We could then move to more precise tracking if/when needed. > > OK, makes sense and I like the MAP_SYNC proposal. I'll change it in my > implementation. Does sys_mmap() reject unknown flag values today? I'm either not looking in the right place or it's missing and we'll need some interface/mechanism to check if MAP_SYNC is honored.
