[Intel-gfx] [PATCH 1/2] shmem: Support for registration of Driver/file owner specific ops

[Joonas Lahtinen]

On ke, 2016-10-19 at 20:41 +0530, akash goel wrote:
> On Thu, Mar 24, 2016 at 5:41 PM, Joonas Lahtinen
> > <joonas.lahtinen at linux.intel.com> wrote:
> > On ke, 2016-03-23 at 11:39 +0530, akash.goel at intel.com wrote:
> > > @@ -34,11 +34,28 @@ struct shmem_sb_info {
> > >       struct mempolicy *mpol;     /* default memory policy for mappings */
> > >  };
> > > 
> > > +struct shmem_dev_info {
> > > +     void *dev_private_data;
> > > +     int (*dev_migratepage)(struct address_space *mapping,
> > > +                            struct page *newpage, struct page *page,
> > > +                            enum migrate_mode mode, void *dev_priv_data);
> > 
> > One might want to have a separate shmem_dev_operations struct or
> > similar.
> > 
> Sorry for the very late turnaround.
> 
> Sorry couldn't get your point here. Are you suggesting to rename the
> structure to shmem_dev_operations ?

I'm pretty sure I was after putting migratepage function pointer in
shmem_dev_operations struct, but I think that can be done once there
are more functions.

s/dev_private_data/private_data/ and s/dev_priv_data/private_data/
might be in order, too. I should be obvious from context.

> > > +};
> > > +
> > >  static inline struct shmem_inode_info *SHMEM_I(struct inode *inode)
> > >  {
> > >       return container_of(inode, struct shmem_inode_info, vfs_inode);
> > >  }
> > > 
> > > +static inline int shmem_set_device_ops(struct address_space *mapping,
> > > +                             struct shmem_dev_info *info)
> > > +{

This name could be shmem_set_dev_info, if there will be separate _ops
struct in future.

> > > +     if (mapping->private_data != NULL)
> > > +             return -EEXIST;
> > > +
> > 
> > I did a quick random peek and most set functions are just void and
> > override existing data. I'd suggest the same.
> > 
> > > 
> > > +     mapping->private_data = info;
> > 
> Fine will change the return type to void and remove the check.
> 
> > 
> > Also, doesn't this kinda steal the mapping->private_data, might that be
> > unexpected for the user? I notice currently it's not being touched at
> > all.
> > 
> Sorry by User do you mean the shmem client who called shmem_file_setup() ?
> It seems clients are not expected to touch mapping->private_data and
> so shmemfs can safely use it.

If it's not used by others, should be fine. Not sure if WARN would be
in place, Chris?

Regards, Joonas
-- 
Joonas Lahtinen
Open Source Technology Center
Intel Corporation