On Mon, 24 Jan 2022, Christoph Hellwig wrote: > On Mon, Jan 24, 2022 at 02:48:32PM +1100, NeilBrown wrote: > > Currently various places test if direct IO is possible on a file by > > checking for the existence of the direct_IO address space operation. > > This is a poor choice, as the direct_IO operation may not be used - it is > > only used if the generic_file_*_iter functions are called for direct IO > > and some filesystems - particularly NFS - don't do this. > > > > Instead, introduce a new f_mode flag: FMODE_CAN_ODIRECT and change the > > various places to check this (avoiding pointer dereferences). > > do_dentry_open() will set this flag if ->direct_IO is present, so > > filesystems do not need to be changed. > > > > NFS *is* changed, to set the flag explicitly and discard the direct_IO > > entry in the address_space_operations for files. > > Looks good: > > Reviewed-by: Christoph Hellwig <hch@xxxxxx> > > It would be nice to throw in a cleanup to remove noop_direct_IO as well. I don't want to add this to the present series. When it lands I'll send patches to the various filesystems to switch to using FMODE_CAN_ODIRECT. Thanks, NeilBrown
