Re: [Nbd] nbd: Add debugfs entries

[Dan Carpenter <dan.carpenter@...57...>]

Hello Markus Pargmann,

The patch 30d53d9c11b6: "nbd: Add debugfs entries" from Aug 17, 2015,
leads to the following static checker warning:

	drivers/block/nbd.c:883 nbd_dev_dbg_init()
	warn: passing zero to 'PTR_ERR'

drivers/block/nbd.c
   875  static int nbd_dev_dbg_init(struct nbd_device *nbd)
   876  {
   877          struct dentry *dir;
   878          struct dentry *f;
   879  
   880          dir = debugfs_create_dir(nbd_name(nbd), nbd_dbg_dir);
   881          if (IS_ERR_OR_NULL(dir)) {
   882                  dev_err(nbd_to_dev(nbd), "Failed to create debugfs dir for '%s' (%ld)\n",
   883                          nbd_name(nbd), PTR_ERR(dir));
   884                  return PTR_ERR(dir);

The static checker warning is that if "dir" is NULL then we return
success.

Debugfs is designed so that we don't need to check for errors.  If
debugfs_create_dir() returns an error pointer that means it isn't
configured in.  The other debugfs functions will be stubbed out so
passing an error pointer to them is harmless.  With this code we print a
lot of warning messages for people who don't enable debugfs in their
.config.  If debugfs is configured but debugfs_create_dir() fails, it
returns NULL.  The other debugfs functions are designed to not care, if
the dir is NULL then they just put the files in the base directory
instead.

My suggestion is that you use debugfs as designed (no error handling)
but the other option would be to fix these error messages and return
values so even though it doesn't work as designed, it at least works.

   885          }
   886          nbd->dbg_dir = dir;

drivers/block/nbd.c:884 nbd_dev_dbg_init() warn: passing zero to 'PTR_ERR'
drivers/block/nbd.c:891 nbd_dev_dbg_init() warn: passing zero to 'PTR_ERR'
drivers/block/nbd.c:892 nbd_dev_dbg_init() warn: passing zero to 'PTR_ERR'
drivers/block/nbd.c:898 nbd_dev_dbg_init() warn: passing zero to 'PTR_ERR'
drivers/block/nbd.c:899 nbd_dev_dbg_init() warn: passing zero to 'PTR_ERR'
drivers/block/nbd.c:905 nbd_dev_dbg_init() warn: passing zero to 'PTR_ERR'
drivers/block/nbd.c:906 nbd_dev_dbg_init() warn: passing zero to 'PTR_ERR'
drivers/block/nbd.c:912 nbd_dev_dbg_init() warn: passing zero to 'PTR_ERR'
drivers/block/nbd.c:913 nbd_dev_dbg_init() warn: passing zero to 'PTR_ERR'
drivers/block/nbd.c:919 nbd_dev_dbg_init() warn: passing zero to 'PTR_ERR'
drivers/block/nbd.c:920 nbd_dev_dbg_init() warn: passing zero to 'PTR_ERR'

regards,
dan carpenter