Re: [PATCH v5 01/10] scsi: scsi_debug: create scsi_debug directory in the debugfs filesystem

[Wenchao Hao]

On 2023/9/28 9:13, Douglas Gilbert wrote:
> On 2023-09-22 05:28, Wenchao Hao wrote:
> > Create directory scsi_debug in the root of the debugfs filesystem.
> > Prepare to add interface for manage error injection.
> >
> > Acked-by: Douglas Gilbert <dgilbert@xxxxxxxxxxxx>
> > Signed-off-by: Wenchao Hao <haowenchao2@xxxxxxxxxx>
> > ---
> >   drivers/scsi/scsi_debug.c | 6 ++++++
> >   1 file changed, 6 insertions(+)
> >
> > diff --git a/drivers/scsi/scsi_debug.c b/drivers/scsi/scsi_debug.c
> > index 9c0af50501f9..35c336271b13 100644
> > --- a/drivers/scsi/scsi_debug.c
> > +++ b/drivers/scsi/scsi_debug.c
> > @@ -41,6 +41,7 @@
> >   #include <linux/random.h>
> >   #include <linux/xarray.h>
> >   #include <linux/prefetch.h>
> > +#include <linux/debugfs.h>
> >   #include <net/checksum.h>
> > @@ -862,6 +863,8 @@ static const int device_qfull_result =
> >   static const int condition_met_result = SAM_STAT_CONDITION_MET;
> > +static struct dentry *sdebug_debugfs_root;
> > +
> >   /* Only do the extra work involved in logical block provisioning if one or
> >    * more of the lbpu, lbpws or lbpws10 parameters are given and we are doing
> > @@ -7011,6 +7014,8 @@ static int __init scsi_debug_init(void)
> >           goto driver_unreg;
> >       }
> > +    sdebug_debugfs_root = debugfs_create_dir("scsi_debug", NULL);
>
> debugfs_create_dir() can fail and return NULL. Looking at other drivers, most
> seem to assume it will work. Since the scsi_debug driver is often used to test
> abnormal situations, perhaps adding something like:
>      if (!sdebug_debugfs_root)
>          pr_info("%s: failed to create initial debugfs directory\n", __func__);
>
> might save someone a bit of time if a NULL dereference on sdebug_debugfs_root
> follows later. That is what the mpt3sas driver does.

Yes, I would fix it by checking return value of debugfs related call
after your review suggestions for other patches.

> Doug Gilbert
>
> > +
> >       for (k = 0; k < hosts_to_add; k++) {
> >           if (want_store && k == 0) {
> >               ret = sdebug_add_host_helper(idx);
> > @@ -7057,6 +7062,7 @@ static void __exit scsi_debug_exit(void)
> >       sdebug_erase_all_stores(false);
> >       xa_destroy(per_store_ap);
> > +    debugfs_remove(sdebug_debugfs_root);
> >   }
> >   device_initcall(scsi_debug_init);