Re: [PATCH/RFC] staging/lustre: Rework class_process_proc_param

[Greg Kroah-Hartman]

On Sat, Mar 18, 2017 at 02:24:08AM -0400, Oleg Drokin wrote:
> Ever since sysfs migration, class_process_proc_param stopped working
> correctly as all the useful params were no longer present as lvars.
> Replace all the nasty fake proc writes with hopefully less nasty
> kobject attribute search and then update the attributes as needed.
> 
> Signed-off-by: Oleg Drokin <green@xxxxxxxxxxxxxx>
> Reported-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
> ---
> Al has quite rightfully complained in the past that class_process_proc_param
> is a terrible piece of code and needs to go.
> This patch is an attempt at improving it somewhat and in process drop
> all the user/kernel address space games we needed to play to make it work
> in the past (and which I suspect attracted Al's attention in the first place).
> 
> Now I wonder if iterating kobject attributes like that would be ok with
> you Greg, or do you think there is a better way?
> class_find_write_attr could be turned into something generic since it's
> certainly convenient to reuse same table of name-write_method pairs,
> but I did some cursory research and nobody else seems to need anything
> of the sort in-tree.
> 
> I know ll_process_config is still awful and I will likely just
> replace the current hack with kset_find_obj, but I just wanted to make
> sure this new approach would be ok before spending too much time on it.
> 
> Thanks!
> 
>  drivers/staging/lustre/lustre/include/obd_class.h  |  4 +-
>  drivers/staging/lustre/lustre/llite/llite_lib.c    | 10 +--
>  drivers/staging/lustre/lustre/lov/lov_obd.c        |  3 +-
>  drivers/staging/lustre/lustre/mdc/mdc_request.c    |  3 +-
>  .../staging/lustre/lustre/obdclass/obd_config.c    | 78 ++++++++++------------
>  drivers/staging/lustre/lustre/osc/osc_request.c    |  3 +-
>  6 files changed, 44 insertions(+), 57 deletions(-)
> 
> diff --git a/drivers/staging/lustre/lustre/include/obd_class.h b/drivers/staging/lustre/lustre/include/obd_class.h
> index 083a6ff..badafb8 100644
> --- a/drivers/staging/lustre/lustre/include/obd_class.h
> +++ b/drivers/staging/lustre/lustre/include/obd_class.h
> @@ -114,8 +114,8 @@ typedef int (*llog_cb_t)(const struct lu_env *, struct llog_handle *,
>  			 struct llog_rec_hdr *, void *);
>  /* obd_config.c */
>  int class_process_config(struct lustre_cfg *lcfg);
> -int class_process_proc_param(char *prefix, struct lprocfs_vars *lvars,
> -			     struct lustre_cfg *lcfg, void *data);
> +int class_process_attr_param(char *prefix, struct kobject *kobj,
> +			     struct lustre_cfg *lcfg);

As you are exporting these functions, they will need to end up with a
lustre_* prefix eventually :)

>  struct obd_device *class_incref(struct obd_device *obd,
>  				const char *scope, const void *source);
>  void class_decref(struct obd_device *obd,
> diff --git a/drivers/staging/lustre/lustre/llite/llite_lib.c b/drivers/staging/lustre/lustre/llite/llite_lib.c
> index 7b80040..192b877 100644
> --- a/drivers/staging/lustre/lustre/llite/llite_lib.c
> +++ b/drivers/staging/lustre/lustre/llite/llite_lib.c
> @@ -2259,7 +2259,7 @@ int ll_obd_statfs(struct inode *inode, void __user *arg)
>  int ll_process_config(struct lustre_cfg *lcfg)
>  {
>  	char *ptr;
> -	void *sb;
> +	struct super_block *sb;
>  	struct lprocfs_static_vars lvars;
>  	unsigned long x;
>  	int rc = 0;
> @@ -2273,15 +2273,15 @@ int ll_process_config(struct lustre_cfg *lcfg)
>  	rc = kstrtoul(ptr, 16, &x);
>  	if (rc != 0)
>  		return -EINVAL;
> -	sb = (void *)x;
> +	sb = (struct super_block *)x;
>  	/* This better be a real Lustre superblock! */
> -	LASSERT(s2lsi((struct super_block *)sb)->lsi_lmd->lmd_magic == LMD_MAGIC);
> +	LASSERT(s2lsi(sb)->lsi_lmd->lmd_magic == LMD_MAGIC);
>  
>  	/* Note we have not called client_common_fill_super yet, so
>  	 * proc fns must be able to handle that!
>  	 */
> -	rc = class_process_proc_param(PARAM_LLITE, lvars.obd_vars,
> -				      lcfg, sb);
> +	rc = class_process_attr_param(PARAM_LLITE, &ll_s2sbi(sb)->ll_kobj,
> +				      lcfg);
>  	if (rc > 0)
>  		rc = 0;
>  	return rc;
> diff --git a/drivers/staging/lustre/lustre/lov/lov_obd.c b/drivers/staging/lustre/lustre/lov/lov_obd.c
> index b3161fb..c33a327 100644
> --- a/drivers/staging/lustre/lustre/lov/lov_obd.c
> +++ b/drivers/staging/lustre/lustre/lov/lov_obd.c
> @@ -926,8 +926,7 @@ int lov_process_config_base(struct obd_device *obd, struct lustre_cfg *lcfg,
>  
>  		lprocfs_lov_init_vars(&lvars);
>  
> -		rc = class_process_proc_param(PARAM_LOV, lvars.obd_vars,
> -					      lcfg, obd);
> +		rc = class_process_attr_param(PARAM_LOV, &obd->obd_kobj, lcfg);
>  		if (rc > 0)
>  			rc = 0;
>  		goto out;
> diff --git a/drivers/staging/lustre/lustre/mdc/mdc_request.c b/drivers/staging/lustre/lustre/mdc/mdc_request.c
> index 6bc2fb8..00387b8 100644
> --- a/drivers/staging/lustre/lustre/mdc/mdc_request.c
> +++ b/drivers/staging/lustre/lustre/mdc/mdc_request.c
> @@ -2670,8 +2670,7 @@ static int mdc_process_config(struct obd_device *obd, u32 len, void *buf)
>  	lprocfs_mdc_init_vars(&lvars);
>  	switch (lcfg->lcfg_command) {
>  	default:
> -		rc = class_process_proc_param(PARAM_MDC, lvars.obd_vars,
> -					      lcfg, obd);
> +		rc = class_process_attr_param(PARAM_MDC, &obd->obd_kobj, lcfg);
>  		if (rc > 0)
>  			rc = 0;
>  		break;
> diff --git a/drivers/staging/lustre/lustre/obdclass/obd_config.c b/drivers/staging/lustre/lustre/obdclass/obd_config.c
> index 8fce88f..08fd126 100644
> --- a/drivers/staging/lustre/lustre/obdclass/obd_config.c
> +++ b/drivers/staging/lustre/lustre/obdclass/obd_config.c
> @@ -995,26 +995,42 @@ int class_process_config(struct lustre_cfg *lcfg)
>  }
>  EXPORT_SYMBOL(class_process_config);
>  
> -int class_process_proc_param(char *prefix, struct lprocfs_vars *lvars,
> -			     struct lustre_cfg *lcfg, void *data)
> +static int class_find_write_attr(struct kobject *kobj, char *name, int namelen,
> +				 char *val, int vallen)
> +{
> +	struct attribute *attr;
> +	struct kobj_type *kt = get_ktype(kobj);
> +	int i;
> +
> +	/* Empty object? */
> +	if (!kt || !kt->default_attrs)
> +		return -ENOENT;
> +
> +	for (i = 0; (attr = kt->default_attrs[i]) != NULL; i++) {
> +		if (!strncmp(attr->name, name, namelen) &&
> +		    namelen == strlen(attr->name)) {

Why do you care about namelen?  Why can't you just do a "normal"
strcmp()?  Is this "untrusted" user data?

> +			if (kt->sysfs_ops && kt->sysfs_ops->store)
> +				return kt->sysfs_ops->store(kobj, attr, val,
> +							    vallen);
> +			return -EINVAL;
> +		}
> +	}
> +
> +	return -ENOENT;
> +}
> +
> +int class_process_attr_param(char *prefix, struct kobject *kobj,
> +			     struct lustre_cfg *lcfg)
>  {
> -	struct lprocfs_vars *var;
> -	struct file fakefile;
> -	struct seq_file fake_seqfile;
>  	char *key, *sval;
>  	int i, keylen, vallen;
> -	int matched = 0, j = 0;
>  	int rc = 0;
> -	int skip = 0;
>  
>  	if (lcfg->lcfg_command != LCFG_PARAM) {
>  		CERROR("Unknown command: %d\n", lcfg->lcfg_command);
>  		return -EINVAL;
>  	}
>  
> -	/* fake a seq file so that var->fops->write can work... */
> -	fakefile.private_data = &fake_seqfile;
> -	fake_seqfile.private = data;
>  	/* e.g. tunefs.lustre --param mdt.group_upcall=foo /r/tmp/lustre-mdt
>  	 * or   lctl conf_param lustre-MDT0000.mdt.group_upcall=bar
>  	 * or   lctl conf_param lustre-OST0000.osc.max_dirty_mb=36
> @@ -1038,39 +1054,16 @@ int class_process_proc_param(char *prefix, struct lprocfs_vars *lvars,
>  		keylen = sval - key;
>  		sval++;
>  		vallen = strlen(sval);
> -		matched = 0;
> -		j = 0;
> -		/* Search proc entries */
> -		while (lvars[j].name) {
> -			var = &lvars[j];
> -			if (!class_match_param(key, var->name, NULL) &&
> -			    keylen == strlen(var->name)) {
> -				matched++;
> -				rc = -EROFS;
> -				if (var->fops && var->fops->write) {
> -					mm_segment_t oldfs;
> -
> -					oldfs = get_fs();
> -					set_fs(KERNEL_DS);
> -					rc = var->fops->write(&fakefile,
> -						(const char __user *)sval,
> -								vallen, NULL);
> -					set_fs(oldfs);
> -				}
> -				break;
> -			}
> -			j++;
> -		}
> -		if (!matched) {
> +		rc = class_find_write_attr(kobj, key, keylen, sval, vallen);
> +
> +		if (rc == -ENOENT) {
>  			CERROR("%.*s: %s unknown param %s\n",
>  			       (int)strlen(prefix) - 1, prefix,
>  			       (char *)lustre_cfg_string(lcfg, 0), key);
>  			/* rc = -EINVAL;	continue parsing other params */
> -			skip++;
>  		} else if (rc < 0) {
> -			CERROR("%s: error writing proc entry '%s': rc = %d\n",
> -			       prefix, var->name, rc);
> -			rc = 0;
> +			CERROR("%s: error writing proc entry '%.*s': rc = %d\n",
> +			       prefix, keylen, key, rc);

It's not a "proc" entry anymore :)

Other than that minor issue, and the question about namelen, this looks
semi-sane to me.  Want to resend this as a non-rfc patch?

thanks,

greg k-h