netdev - Re: [PATCH net-next 2/6] net: make dev_alloc_name() call dev_prep_valid

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Date: Fri, 20 Oct 2023 12:24:57 +0200
From: Jiri Pirko <jiri@...nulli.us>
To: Jakub Kicinski <kuba@...nel.org>
Cc: davem@...emloft.net, netdev@...r.kernel.org, edumazet@...gle.com,
	pabeni@...hat.com, johannes.berg@...el.com, mpe@...erman.id.au,
	j@...fi
Subject: Re: [PATCH net-next 2/6] net: make dev_alloc_name() call
 dev_prep_valid_name()

Fri, Oct 20, 2023 at 03:18:52AM CEST, kuba@...nel.org wrote:
>__dev_alloc_name() handles both the sprintf and non-sprintf
>target names. This complicates the code.
>
>dev_prep_valid_name() already handles the non-sprintf case,
>before calling __dev_alloc_name(), make the only other caller
>also go thru dev_prep_valid_name(). This way we can drop
>the non-sprintf handling in __dev_alloc_name() in one of
>the next changes.
>
>commit 55a5ec9b7710 ("Revert "net: core: dev_get_valid_name is now the same as dev_alloc_name_ns"") and
>commit 029b6d140550 ("Revert "net: core: maybe return -EEXIST in __dev_alloc_name"")
>tell us that we can't start returning -EEXIST from dev_alloc_name()
>on name duplicates. Bite the bullet and pass the expected errno to
>dev_prep_valid_name().
>
>dev_prep_valid_name() must now propagate out the allocated id
>for printf names.
>
>Signed-off-by: Jakub Kicinski <kuba@...nel.org>
>---
> net/core/dev.c | 20 +++++++++++---------
> 1 file changed, 11 insertions(+), 9 deletions(-)
>
>diff --git a/net/core/dev.c b/net/core/dev.c
>index 874c7daa81f5..004e9f26b160 100644
>--- a/net/core/dev.c
>+++ b/net/core/dev.c
>@@ -1137,19 +1137,18 @@ static int __dev_alloc_name(struct net *net, const char *name, char *res)
> 	return -ENFILE;
> }
> 
>+/* Returns negative errno or allocated unit id (see __dev_alloc_name()) */
> static int dev_prep_valid_name(struct net *net, struct net_device *dev,
>-			       const char *want_name, char *out_name)
>+			       const char *want_name, char *out_name,
>+			       int dup_errno)
> {
>-	int ret;
>-
> 	if (!dev_valid_name(want_name))
> 		return -EINVAL;
> 
> 	if (strchr(want_name, '%')) {
>-		ret = __dev_alloc_name(net, want_name, out_name);
>-		return ret < 0 ? ret : 0;
>+		return __dev_alloc_name(net, want_name, out_name);
> 	} else if (netdev_name_in_use(net, want_name)) {
>-		return -EEXIST;
>+		return -dup_errno;
> 	} else if (out_name != want_name) {
> 		strscpy(out_name, want_name, IFNAMSIZ);
> 	}
>@@ -1173,14 +1172,17 @@ static int dev_prep_valid_name(struct net *net, struct net_device *dev,
> 
> int dev_alloc_name(struct net_device *dev, const char *name)
> {
>-	return __dev_alloc_name(dev_net(dev), name, dev->name);
>+	return dev_prep_valid_name(dev_net(dev), dev, name, dev->name, ENFILE);
> }
> EXPORT_SYMBOL(dev_alloc_name);
> 
> static int dev_get_valid_name(struct net *net, struct net_device *dev,
> 			      const char *name)
> {
>-	return dev_prep_valid_name(net, dev, name, dev->name);
>+	int ret;
>+
>+	ret = dev_prep_valid_name(net, dev, name, dev->name, EEXIST);
>+	return ret < 0 ? ret : 0;

Why can't you just return dev_prep_valid_name() ?

No caller seems to care about ret > 0


> }
> 
> /**
>@@ -11118,7 +11120,7 @@ int __dev_change_net_namespace(struct net_device *dev, struct net *net,
> 		/* We get here if we can't use the current device name */
> 		if (!pat)
> 			goto out;
>-		err = dev_prep_valid_name(net, dev, pat, new_name);
>+		err = dev_prep_valid_name(net, dev, pat, new_name, EEXIST);
> 		if (err < 0)
> 			goto out;
> 	}
>-- 
>2.41.0
>