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

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Date:   Thu, 28 Sep 2023 09:38:55 +0800
From:   Wenchao Hao <haowenchao2@...wei.com>
To:     <dgilbert@...erlog.com>,
        "James E . J . Bottomley" <jejb@...ux.ibm.com>,
        "Martin K . Petersen" <martin.petersen@...cle.com>,
        <open-iscsi@...glegroups.com>, <linux-scsi@...r.kernel.org>
CC:     <linux-kernel@...r.kernel.org>, <louhongxiang@...wei.com>
Subject: Re: [PATCH v5 01/10] scsi: scsi_debug: create scsi_debug directory in
 the debugfs filesystem

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@...erlog.com>
>> Signed-off-by: Wenchao Hao <haowenchao2@...wei.com>
>> ---
>>   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);
> 
>