On Mon, Oct 10, 2016 at 05:07:45PM +1100, Dave Chinner wrote: > > > *However*, the DAX IO path locking in XFS has changed in 4.9-rc1 to > > > match the buffered IO single writer POSIX semantics - the test is a > > > bad test based on the fact it exercised a path that is under heavy > > > development and so can't be used as a regression test across > > > multiple kernels. > > > > That being said - I wonder if we should allow the shared lock on DAX > > files IFF the user is specifying O_DIRECT in the open mode.. > > It should do - if it doesn't then we screwed up the IO path > selection logic in XFS and we'll need to fix it. Depends on your defintion of "we". The DAX code has always abused the direct I/O path, and that abuse is ingrained in the VFS path in a way that we can't easily undo it in XFS, e.g. take a look at io_is_direct and iocb_flags in include/linux/fs.h, which ensure that DAX I/O will always appear as IOCB_DIRECT to the fs. It will take some time to untagle this, but it's on my todo list once the last file system (ext4) untangles the DAX and direct I/O path. -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
