Re: [PATCH v3 12/14] fs/configfs: Add a callback to determine attribute visibility

[Tom Lendacky]

On 4/16/24 00:46, Dan Williams wrote:
> Tom Lendacky wrote:
> > In order to support dynamic decisions as to whether an attribute should be
> > created, add a callback that returns a bool to indicate whether the
> > attribute should be display. If no callback is registered, the attribute
>
> s/display/displayed/

Will fix.

> > is displayed by default.
> >
> > Cc: Joel Becker <jlbec@xxxxxxxxxxxx>
> > Cc: Christoph Hellwig <hch@xxxxxx>
> > Signed-off-by: Tom Lendacky <thomas.lendacky@xxxxxxx>
> > ---
> >   fs/configfs/file.c       |   7 +++
> >   include/linux/configfs.h | 111 +++++++++++++++++++++++++++------------
> >   2 files changed, 84 insertions(+), 34 deletions(-)
> >
> > diff --git a/fs/configfs/file.c b/fs/configfs/file.c
> > index 0ad32150611e..a976c183756c 100644
> > --- a/fs/configfs/file.c
> > +++ b/fs/configfs/file.c
> > @@ -451,6 +451,9 @@ int configfs_create_file(struct config_item * item, const struct configfs_attrib
> >   	umode_t mode = (attr->ca_mode & S_IALLUGO) | S_IFREG;
> >   	int error = 0;
> >   
> > +	if (attr->is_visible && !attr->is_visible(item, attr))
> > +		return 0;
> > +
> >   	inode_lock_nested(d_inode(dir), I_MUTEX_NORMAL);
> >   	error = configfs_make_dirent(parent_sd, NULL, (void *) attr, mode,
> >   				     CONFIGFS_ITEM_ATTR, parent_sd->s_frag);
> > @@ -470,9 +473,13 @@ int configfs_create_bin_file(struct config_item *item,
> >   {
> >   	struct dentry *dir = item->ci_dentry;
> >   	struct configfs_dirent *parent_sd = dir->d_fsdata;
> > +	const struct configfs_attribute *attr = &bin_attr->cb_attr;
> >   	umode_t mode = (bin_attr->cb_attr.ca_mode & S_IALLUGO) | S_IFREG;
> >   	int error = 0;
> >   
> > +	if (attr->is_visible && !attr->is_visible(item, attr))
> > +		return 0;
> > +
> >   	inode_lock_nested(dir->d_inode, I_MUTEX_NORMAL);
> >   	error = configfs_make_dirent(parent_sd, NULL, (void *) bin_attr, mode,
> >   				     CONFIGFS_ITEM_BIN_ATTR, parent_sd->s_frag);
> > diff --git a/include/linux/configfs.h b/include/linux/configfs.h
> > index 2606711adb18..c836d7bc7c9e 100644
> > --- a/include/linux/configfs.h
> > +++ b/include/linux/configfs.h
> > @@ -116,35 +116,57 @@ struct configfs_attribute {
> >   	const char		*ca_name;
> >   	struct module 		*ca_owner;
> >   	umode_t			ca_mode;
> > +	bool (*is_visible)(const struct config_item *, const struct configfs_attribute *);
> >   	ssize_t (*show)(struct config_item *, char *);
> >   	ssize_t (*store)(struct config_item *, const char *, size_t);
> >   };
> >   
> > -#define CONFIGFS_ATTR(_pfx, _name)			\
> > +#define __CONFIGFS_ATTR(_pfx, _name, _vis)		\
> >   static struct configfs_attribute _pfx##attr_##_name = {	\
> >   	.ca_name	= __stringify(_name),		\
> >   	.ca_mode	= S_IRUGO | S_IWUSR,		\
> >   	.ca_owner	= THIS_MODULE,			\
> > +	.is_visible	= _vis,				\
> >   	.show		= _pfx##_name##_show,		\
> >   	.store		= _pfx##_name##_store,		\
>
> Shouldn't this operation live in configfs_group_operations? That would
> mirror the sysfs organization, and likely saves some memory.

I suppose it can, but then you lose the grouping of attributes within 
the same directory, right? A configfs group will result in moving the 
entries into a subdirectory, right? If we go with the group level, then 
we will be moving the existing TSM extra attributes and the new TSM SVSM 
attributes into new, separate sub-directories.

Thanks,
Tom