Messages in this thread | | | Date | Mon, 9 Dec 2013 00:55:26 -0800 | From | Greg KH <> | Subject | Re: [PATCH] xen/debugfs: Check debugfs initialization before using it |
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On Mon, Dec 09, 2013 at 04:44:05PM +0800, Ethan Zhao wrote: > On Mon, Dec 9, 2013 at 4:25 PM, Greg KH <gregkh@linuxfoundation.org> wrote: > > On Mon, Dec 09, 2013 at 09:43:16AM +0800, Ethan Zhao wrote: > >> On Sun, Dec 8, 2013 at 10:01 PM, Greg KH <gregkh@linuxfoundation.org> wrote: > >> > On Sun, Dec 08, 2013 at 07:31:02PM +0800, ethan.zhao wrote: > >> >> Should check debugfs initialization with debugfs_initialized() before using it, > >> >> Because if it isn't initialized, the return value of fake debugfs_create_dir() etc > >> >> functions would be ERR_PTR(-ENODEV), checking with NULL will not work. > >> > > >> > So? It should "just work" without this check, right? What happens if > >> > your patch isn't applied and debugfs isn't enabled? > >> > >> If debugfs isn't configured, debugfs_initialized() and other > >> functions are defined as following, > >> > >> static inline bool debugfs_initialized(void) > >> { > >> return false; > >> } > >> > >> static inline struct dentry *debugfs_create_file(const char *name, umode_t mode, > >> struct dentry *parent, void *data, > >> const struct file_operations *fops) > >> { > >> return ERR_PTR(-ENODEV); > >> } > >> > >> static inline struct dentry *debugfs_create_dir(const char *name, > >> struct dentry *parent) > >> { > >> return ERR_PTR(-ENODEV); > >> } > >> > >> And the checking code in xen\debugfs.c xen_init_debugfs() will not > >> work, the return value is not NULL. > >> d_xen_debug = debugfs_create_dir("xen", NULL); > >> > >> if (!d_xen_debug) > >> pr_warning("Could not create 'xen' debugfs directory\n"); > > > > Which is just fine, what is wrong with this? > > If we no check with debugfs_initialized(), the above code should be > if (!d_xen_debug || IS_ERR (d_xen_debug)) > pr_warning("Could not create 'xen' debugfs directory\n");
No, you don't want to print out that message if debugfs is not enabled.
You really don't want to print anything out, as what can a user do about this?
I still think the original code is correct, have you tried it with debugfs disabled?
greg k-h
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