On Tue, Jul 21, 2020 at 05:41:32PM +0200, Christoph Hellwig wrote: > On Tue, Jul 21, 2020 at 08:27:54AM -0700, Darrick J. Wong wrote: > > On Tue, Jul 21, 2020 at 05:16:16PM +0200, Christoph Hellwig wrote: > > > On Tue, Jul 21, 2020 at 04:14:37PM +0100, Matthew Wilcox wrote: > > > > On Tue, Jul 21, 2020 at 05:06:15PM +0200, Christoph Hellwig wrote: > > > > > On Tue, Jul 21, 2020 at 04:04:32PM +0100, Matthew Wilcox wrote: > > > > > > I thought you were going to respin this with EREMCHG changed to ENOTBLK? > > > > > > > > > > Oh, true. I'll do that ASAP. > > > > > > > > Michael, could we add this to manpages? > > > > > > Umm, no. -ENOTBLK is internal - the file systems will retry using > > > buffered I/O and the error shall never escape to userspace (or even the > > > VFS for that matter). > > > > It's worth dropping a comment somewhere that ENOTBLK is the desired > > "fall back to buffered" errcode, seeing as Dave and I missed that in > > XFS... > > Sounds like a good idea, but what would a good place be? In the comment that precedes iomap_dio_rw() for the iomap version, and... ...ye $deity, the old direct-io.c file is a mess of wrappers. Uh... a new comment preceding __blockdev_direct_IO? Or blockdev_direct_IO? Or both? Or I guess the direct_IO documentation in vfs.rst...? ``direct_IO`` called by the generic read/write routines to perform direct_IO - that is IO requests which bypass the page cache and transfer data directly between the storage and the application's address space. This function can return -ENOTBLK to signal that it is necessary to fallback to buffered IO. Note that blockdev_direct_IO and variants can also return -ENOTBLK. --D
