Re: [PATCH 01/21] mtip32xx: Remove redundant null pointer checks in mtip_hw_debugfs_init()

[Jens Axboe <axboe@kernel.dk>]

On 9/3/24 7:18 PM, Li Zetao wrote:
> Hi,
> 
> ? 2024/9/3 22:47, Jens Axboe ??:
>> On 9/3/24 8:43 AM, Li Zetao wrote:
>>> Since the debugfs_create_dir() never returns a null pointer, checking
>>> the return value for a null pointer is redundant, and using IS_ERR is
>>> safe enough.
>>
>> Sigh, why are we seeing so many odd variants of this recently. If you'd
>> do a bit of searching upfront, you'd find that these should not be
>> checked at all rather than changing it from err+null to just an error
>> pointer check.
>>
>> So no to this one, please do at least a tiny bit of research first
>> before blindly making a change based on what some static analyzer told
>> you.
>>
> I have researched in the community before making the modification.
> debugfs_create_file can handle illegal dentry, but my understanding is
> that verifying debugfs_create_dir when it fails can avoid invalid
> calls to debugfs_create_file.
> 
> Greg suggested that I remove this check, maybe I can modify it in v2?

debugfs should tolerate error pointers, hence all the error checking
should just go away rather than being modified. Something ala the below,
totally untested.


diff --git a/drivers/block/mtip32xx/mtip32xx.c b/drivers/block/mtip32xx/mtip32xx.c
index c6ef0546ffc9..11901f2812ad 100644
--- a/drivers/block/mtip32xx/mtip32xx.c
+++ b/drivers/block/mtip32xx/mtip32xx.c
@@ -2269,25 +2269,12 @@ static const struct file_operations mtip_flags_fops = {
 	.llseek = no_llseek,
 };
 
-static int mtip_hw_debugfs_init(struct driver_data *dd)
+static void mtip_hw_debugfs_init(struct driver_data *dd)
 {
-	if (!dfs_parent)
-		return -1;
-
 	dd->dfs_node = debugfs_create_dir(dd->disk->disk_name, dfs_parent);
-	if (IS_ERR_OR_NULL(dd->dfs_node)) {
-		dev_warn(&dd->pdev->dev,
-			"Error creating node %s under debugfs\n",
-						dd->disk->disk_name);
-		dd->dfs_node = NULL;
-		return -1;
-	}
-
 	debugfs_create_file("flags", 0444, dd->dfs_node, dd, &mtip_flags_fops);
 	debugfs_create_file("registers", 0444, dd->dfs_node, dd,
 			    &mtip_regs_fops);
-
-	return 0;
 }
 
 static void mtip_hw_debugfs_exit(struct driver_data *dd)
@@ -4043,10 +4030,6 @@ static int __init mtip_init(void)
 	mtip_major = error;
 
 	dfs_parent = debugfs_create_dir("rssd", NULL);
-	if (IS_ERR_OR_NULL(dfs_parent)) {
-		pr_warn("Error creating debugfs parent\n");
-		dfs_parent = NULL;
-	}
 
 	/* Register our PCI operations. */
 	error = pci_register_driver(&mtip_pci_driver);


-- 
Jens Axboe