The origin ax25_dev_list implements its own single linked list,
which is complicated and error-prone. For example, when deleting
the node of ax25_dev_list in ax25_dev_device_down(), we have to
operate on the head node and other nodes separately.
This patch uses kernel universal linked list to replace original
ax25_dev_list, which make the operation of ax25_dev_list easier.
There are two points that need to notice:
[1] We should add a check to judge whether the list is empty before
INIT_LIST_HEAD in ax25_dev_device_up(), otherwise it will empty the
list for each new ax25_dev added.
[2] We should do "dev->ax25_ptr = ax25_dev;" and "dev->ax25_ptr = NULL;"
while holding the spinlock, otherwise the ax25_dev_device_up() and
ax25_dev_device_down() could race, we're not guaranteed to find a match
ax25_dev in ax25_dev_device_down().
Suggested-by: Dan Carpenter <dan.carpenter@linaro.org>
Signed-off-by: Duoming Zhou <duoming@zju.edu.cn>
---
include/net/ax25.h | 3 +--
net/ax25/ax25_dev.c | 43 ++++++++++++++++++-------------------------
2 files changed, 19 insertions(+), 27 deletions(-)
diff --git a/include/net/ax25.h b/include/net/ax25.h
index 0d939e5aee4..c2a85fd3f5e 100644
--- a/include/net/ax25.h
+++ b/include/net/ax25.h
@@ -216,7 +216,7 @@ typedef struct {
struct ctl_table;
typedef struct ax25_dev {
- struct ax25_dev *next;
+ struct list_head list;
struct net_device *dev;
netdevice_tracker dev_tracker;
@@ -330,7 +330,6 @@ int ax25_addr_size(const ax25_digi *);
void ax25_digi_invert(const ax25_digi *, ax25_digi *);
/* ax25_dev.c */
-extern ax25_dev *ax25_dev_list;
extern spinlock_t ax25_dev_lock;
#if IS_ENABLED(CONFIG_AX25)
diff --git a/net/ax25/ax25_dev.c b/net/ax25/ax25_dev.c
index 282ec581c07..1557f879377 100644
--- a/net/ax25/ax25_dev.c
+++ b/net/ax25/ax25_dev.c
@@ -22,11 +22,12 @@
#include <net/sock.h>
#include <linux/uaccess.h>
#include <linux/fcntl.h>
+#include <linux/list.h>
#include <linux/mm.h>
#include <linux/interrupt.h>
#include <linux/init.h>
-ax25_dev *ax25_dev_list;
+static struct list_head ax25_dev_list;
DEFINE_SPINLOCK(ax25_dev_lock);
ax25_dev *ax25_addr_ax25dev(ax25_address *addr)
@@ -34,7 +35,7 @@ ax25_dev *ax25_addr_ax25dev(ax25_address *addr)
ax25_dev *ax25_dev, *res = NULL;
spin_lock_bh(&ax25_dev_lock);
- for (ax25_dev = ax25_dev_list; ax25_dev != NULL; ax25_dev = ax25_dev->next)
+ list_for_each_entry(ax25_dev, &ax25_dev_list, list)
if (ax25cmp(addr, (const ax25_address *)ax25_dev->dev->dev_addr) == 0) {
res = ax25_dev;
ax25_dev_hold(ax25_dev);
@@ -52,6 +53,9 @@ void ax25_dev_device_up(struct net_device *dev)
{
ax25_dev *ax25_dev;
+ /* Initialized the list for the first entry */
+ if (!ax25_dev_list.next)
+ INIT_LIST_HEAD(&ax25_dev_list);
ax25_dev = kzalloc(sizeof(*ax25_dev), GFP_KERNEL);
if (!ax25_dev) {
printk(KERN_ERR "AX.25: ax25_dev_device_up - out of memory\n");
@@ -59,7 +63,6 @@ void ax25_dev_device_up(struct net_device *dev)
}
refcount_set(&ax25_dev->refcount, 1);
- dev->ax25_ptr = ax25_dev;
ax25_dev->dev = dev;
netdev_hold(dev, &ax25_dev->dev_tracker, GFP_KERNEL);
ax25_dev->forward = NULL;
@@ -85,8 +88,8 @@ void ax25_dev_device_up(struct net_device *dev)
#endif
spin_lock_bh(&ax25_dev_lock);
- ax25_dev->next = ax25_dev_list;
- ax25_dev_list = ax25_dev;
+ list_add(&ax25_dev->list, &ax25_dev_list);
+ dev->ax25_ptr = ax25_dev;
spin_unlock_bh(&ax25_dev_lock);
ax25_dev_hold(ax25_dev);
@@ -111,32 +114,25 @@ void ax25_dev_device_down(struct net_device *dev)
/*
* Remove any packet forwarding that points to this device.
*/
- for (s = ax25_dev_list; s != NULL; s = s->next)
+ list_for_each_entry(s, &ax25_dev_list, list)
if (s->forward == dev)
s->forward = NULL;
- if ((s = ax25_dev_list) == ax25_dev) {
- ax25_dev_list = s->next;
- goto unlock_put;
- }
-
- while (s != NULL && s->next != NULL) {
- if (s->next == ax25_dev) {
- s->next = ax25_dev->next;
+ list_for_each_entry(s, &ax25_dev_list, list) {
+ if (s == ax25_dev) {
+ list_del(&s->list);
goto unlock_put;
}
-
- s = s->next;
}
- spin_unlock_bh(&ax25_dev_lock);
dev->ax25_ptr = NULL;
+ spin_unlock_bh(&ax25_dev_lock);
ax25_dev_put(ax25_dev);
return;
unlock_put:
+ dev->ax25_ptr = NULL;
spin_unlock_bh(&ax25_dev_lock);
ax25_dev_put(ax25_dev);
- dev->ax25_ptr = NULL;
netdev_put(dev, &ax25_dev->dev_tracker);
ax25_dev_put(ax25_dev);
}
@@ -200,16 +196,13 @@ struct net_device *ax25_fwd_dev(struct net_device *dev)
*/
void __exit ax25_dev_free(void)
{
- ax25_dev *s, *ax25_dev;
+ ax25_dev *s, *n;
spin_lock_bh(&ax25_dev_lock);
- ax25_dev = ax25_dev_list;
- while (ax25_dev != NULL) {
- s = ax25_dev;
- netdev_put(ax25_dev->dev, &ax25_dev->dev_tracker);
- ax25_dev = ax25_dev->next;
+ list_for_each_entry_safe(s, n, &ax25_dev_list, list) {
+ netdev_put(s->dev, &s->dev_tracker);
+ list_del(&s->list);
kfree(s);
}
- ax25_dev_list = NULL;
spin_unlock_bh(&ax25_dev_lock);
}
--
2.17.1On Tue, May 07, 2024 at 03:03:39PM GMT, Duoming Zhou wrote:
> typedef struct ax25_dev {
> - struct ax25_dev *next;
> + struct list_head list;
Would it make sense to replace this with:
LIST_HEAD(ax25_dev_list);
And then get rid of:
> + /* Initialized the list for the first entry */
> + if (!ax25_dev_list.next)
> + INIT_LIST_HEAD(&ax25_dev_list);
--
Lars Kellogg-Stedman <lars@oddbit.com> | larsks @ {irc,twitter,github}
http://blog.oddbit.com/ | N1LKS
On Tue, May 07, 2024 at 03:43:11PM GMT, Lars Kellogg-Stedman wrote:
> On Tue, May 07, 2024 at 03:03:39PM GMT, Duoming Zhou wrote:
> > typedef struct ax25_dev {
> > - struct ax25_dev *next;
> > + struct list_head list;
>
> Would it make sense to replace this with:
>
> LIST_HEAD(ax25_dev_list);
Sorry, *this*:
> +static struct list_head ax25_dev_list;
--
Lars Kellogg-Stedman <lars@oddbit.com> | larsks @ {irc,twitter,github}
http://blog.oddbit.com/ | N1LKS
On 2024-05-07 at 12:33:39, Duoming Zhou (duoming@zju.edu.cn) wrote:
> The origin ax25_dev_list implements its own single linked list,
> which is complicated and error-prone. For example, when deleting
> the node of ax25_dev_list in ax25_dev_device_down(), we have to
> operate on the head node and other nodes separately.
>
> This patch uses kernel universal linked list to replace original
> ax25_dev_list, which make the operation of ax25_dev_list easier.
> There are two points that need to notice:
>
> [1] We should add a check to judge whether the list is empty before
> INIT_LIST_HEAD in ax25_dev_device_up(), otherwise it will empty the
> list for each new ax25_dev added.
>
> [2] We should do "dev->ax25_ptr = ax25_dev;" and "dev->ax25_ptr = NULL;"
> while holding the spinlock, otherwise the ax25_dev_device_up() and
> ax25_dev_device_down() could race, we're not guaranteed to find a match
> ax25_dev in ax25_dev_device_down().
>
> Suggested-by: Dan Carpenter <dan.carpenter@linaro.org>
> Signed-off-by: Duoming Zhou <duoming@zju.edu.cn>
> -ax25_dev *ax25_dev_list;
> +static struct list_head ax25_dev_list;
> DEFINE_SPINLOCK(ax25_dev_lock);
>
> ax25_dev *ax25_addr_ax25dev(ax25_address *addr)
> @@ -34,7 +35,7 @@ ax25_dev *ax25_addr_ax25dev(ax25_address *addr)
> ax25_dev *ax25_dev, *res = NULL;
>
> spin_lock_bh(&ax25_dev_lock);
> - for (ax25_dev = ax25_dev_list; ax25_dev != NULL; ax25_dev = ax25_dev->next)
> + list_for_each_entry(ax25_dev, &ax25_dev_list, list)
> if (ax25cmp(addr, (const ax25_address *)ax25_dev->dev->dev_addr) == 0) {
> res = ax25_dev;
> ax25_dev_hold(ax25_dev);
> @@ -52,6 +53,9 @@ void ax25_dev_device_up(struct net_device *dev)
> {
> ax25_dev *ax25_dev;
>
> + /* Initialized the list for the first entry */
> + if (!ax25_dev_list.next)
> + INIT_LIST_HEAD(&ax25_dev_list);
if you define ax25_dev_list using 'static LIST_HEAD(ax25_dev_list)', you need this conditional check and
initialization ?
> ax25_dev = kzalloc(sizeof(*ax25_dev), GFP_KERNEL);
> if (!ax25_dev) {
> printk(KERN_ERR "AX.25: ax25_dev_device_up - out of memory\n");
> @@ -59,7 +63,6 @@ void ax25_dev_device_up(struct net_device *dev)
> }
>
> refcount_set(&ax25_dev->refcount, 1);
>
On Tue, May 07, 2024 at 02:59:17PM +0530, Ratheesh Kannoth wrote:
> On 2024-05-07 at 12:33:39, Duoming Zhou (duoming@zju.edu.cn) wrote:
> > The origin ax25_dev_list implements its own single linked list,
> > which is complicated and error-prone. For example, when deleting
> > the node of ax25_dev_list in ax25_dev_device_down(), we have to
> > operate on the head node and other nodes separately.
> >
> > This patch uses kernel universal linked list to replace original
> > ax25_dev_list, which make the operation of ax25_dev_list easier.
> > There are two points that need to notice:
> >
> > [1] We should add a check to judge whether the list is empty before
> > INIT_LIST_HEAD in ax25_dev_device_up(), otherwise it will empty the
> > list for each new ax25_dev added.
> >
> > [2] We should do "dev->ax25_ptr = ax25_dev;" and "dev->ax25_ptr = NULL;"
> > while holding the spinlock, otherwise the ax25_dev_device_up() and
> > ax25_dev_device_down() could race, we're not guaranteed to find a match
> > ax25_dev in ax25_dev_device_down().
> >
> > Suggested-by: Dan Carpenter <dan.carpenter@linaro.org>
> > Signed-off-by: Duoming Zhou <duoming@zju.edu.cn>
> > -ax25_dev *ax25_dev_list;
> > +static struct list_head ax25_dev_list;
> > DEFINE_SPINLOCK(ax25_dev_lock);
> >
> > ax25_dev *ax25_addr_ax25dev(ax25_address *addr)
> > @@ -34,7 +35,7 @@ ax25_dev *ax25_addr_ax25dev(ax25_address *addr)
> > ax25_dev *ax25_dev, *res = NULL;
> >
> > spin_lock_bh(&ax25_dev_lock);
> > - for (ax25_dev = ax25_dev_list; ax25_dev != NULL; ax25_dev = ax25_dev->next)
> > + list_for_each_entry(ax25_dev, &ax25_dev_list, list)
> > if (ax25cmp(addr, (const ax25_address *)ax25_dev->dev->dev_addr) == 0) {
> > res = ax25_dev;
> > ax25_dev_hold(ax25_dev);
> > @@ -52,6 +53,9 @@ void ax25_dev_device_up(struct net_device *dev)
> > {
> > ax25_dev *ax25_dev;
> >
> > + /* Initialized the list for the first entry */
> > + if (!ax25_dev_list.next)
> > + INIT_LIST_HEAD(&ax25_dev_list);
> if you define ax25_dev_list using 'static LIST_HEAD(ax25_dev_list)', you need this conditional check and
> initialization ?
>
Ah, yes. That's the proper way to do it.
regards,
dan carpenter
> … that need to notice: I suggest to improve such a wording. > [1] We should add a check to judge whether … Are imperative wordings more desirable for improved change descriptions? https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/process/submitting-patches.rst?h=v6.9-rc7#n94 Regards, Markus
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