Re: [PATCH V9 10/11] fs/xfs: Update xfs_ioctl_setattr_dax_invalidate()
From: Dave Chinner
Date: Tue Apr 21 2020 - 17:31:00 EST
On Tue, Apr 21, 2020 at 01:31:40PM -0700, Darrick J. Wong wrote:
> On Tue, Apr 21, 2020 at 12:17:52PM -0700, ira.weiny@xxxxxxxxx wrote:
> > From: Ira Weiny <ira.weiny@xxxxxxxxx>
> >
> > Because of the separation of FS_XFLAG_DAX from S_DAX and the delayed
> > setting of S_DAX, data invalidation no longer needs to happen when
> > FS_XFLAG_DAX is changed.
> >
> > Change xfs_ioctl_setattr_dax_invalidate() to be
> > xfs_ioctl_dax_check_set_cache() and alter the code to reflect the new
> > functionality.
> >
> > Furthermore, we no longer need the locking so we remove the join_flags
> > logic.
> >
> > Signed-off-by: Ira Weiny <ira.weiny@xxxxxxxxx>
> >
> > ---
> > Changes from V8:
> > Change name of function to xfs_ioctl_dax_check_set_cache()
> > Update commit message
> > Fix bit manipulations
> >
> > Changes from V7:
> > Use new flag_inode_dontcache()
> > Skip don't cache if mount over ride is active.
> >
> > Changes from v6:
> > Fix completely broken implementation and update commit message.
> > Use the new VFS layer I_DONTCACHE to facilitate inode eviction
> > and S_DAX changing on drop_caches
> >
> > Changes from v5:
> > New patch
> > ---
> > fs/xfs/xfs_ioctl.c | 108 +++++++++------------------------------------
> > 1 file changed, 20 insertions(+), 88 deletions(-)
> >
> > diff --git a/fs/xfs/xfs_ioctl.c b/fs/xfs/xfs_ioctl.c
> > index 104495ac187c..b87b571a6748 100644
> > --- a/fs/xfs/xfs_ioctl.c
> > +++ b/fs/xfs/xfs_ioctl.c
> > @@ -1245,64 +1245,26 @@ xfs_ioctl_setattr_xflags(
> > return 0;
> > }
> >
> > -/*
> > - * If we are changing DAX flags, we have to ensure the file is clean and any
> > - * cached objects in the address space are invalidated and removed. This
> > - * requires us to lock out other IO and page faults similar to a truncate
> > - * operation. The locks need to be held until the transaction has been committed
> > - * so that the cache invalidation is atomic with respect to the DAX flag
> > - * manipulation.
> > - */
> > -static int
> > -xfs_ioctl_setattr_dax_invalidate(
> > +static void
> > +xfs_ioctl_dax_check_set_cache(
>
> That's a ... strange name. Set cache on what?
>
> Oh, this is the function that sets I_DONTCACHE if an FS_XFLAG_DAX change
> could have an immediate effect on S_DAX (assuming no other users). What
> do you think of the following?
>
> /*
> * If a change to FS_XFLAG_DAX will result in an change to S_DAX
> * the next time the incore inode is initialized, set the VFS
> * I_DONTCACHE flag to try to hurry that along.
> */
> static void
> xfs_ioctl_try_change_vfs_dax(...)
That doesn't seem any better. This is a preparation function now, in
that it can't fail and doesn't change the outcome of the operation
being performed. So, IMO, calling it something like
xfs_ioctl_setattr_prepare_dax() would be a better name for it.
Cheers,
Dave.
--
Dave Chinner
david@xxxxxxxxxxxxx