Messages in this thread | | | Date | Tue, 25 Aug 2015 14:08:58 -0700 | From | Andrew Morton <> | Subject | Re: [PATCH] mm/backing-dev: Check return value of the debugfs_create_dir() |
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On Tue, 25 Aug 2015 13:54:23 +0600 Alexander Kuleshov <kuleshovmail@gmail.com> wrote:
> The debugfs_create_dir() function may fail and return error. If the > root directory not created, we can't create anything inside it. This > patch adds check for this case. > > ... > > --- a/mm/backing-dev.c > +++ b/mm/backing-dev.c > @@ -117,15 +117,21 @@ static const struct file_operations bdi_debug_stats_fops = { > > static void bdi_debug_register(struct backing_dev_info *bdi, const char *name) > { > - bdi->debug_dir = debugfs_create_dir(name, bdi_debug_root); > - bdi->debug_stats = debugfs_create_file("stats", 0444, bdi->debug_dir, > - bdi, &bdi_debug_stats_fops); > + if (bdi_debug_root) { > + bdi->debug_dir = debugfs_create_dir(name, bdi_debug_root); > + if (bdi->debug_dir) > + bdi->debug_stats = debugfs_create_file("stats", 0444, > + bdi->debug_dir, bdi, > + &bdi_debug_stats_fops); > + }
If debugfs_create_dir() fails, debugfs_create_file() will go ahead and attempt to create the debugfs file in the debugfs root directory:
: static struct dentry *start_creating(const char *name, struct dentry *parent) : { : ... : /* If the parent is not specified, we create it in the root. : * We need the root dentry to do this, which is in the super : * block. A pointer to that is in the struct vfsmount that we : * have around. : */ : if (!parent) : parent = debugfs_mount->mnt_root;
I'm not sure that this is very useful behaviour, and putting the files in the wrong place is a very obscure way of informing the user that debugfs_create_dir() failed :(
I don't think it's worth making little changes such as this - handling debugfs failures needs a deeper rethink.
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