| Message ID | bd49e83817604e61a12c9bf688a0825f116e67c0.1715065005.git.duoming@zju.edu.cn (mailing list archive) |
|---|---|
| State | Superseded |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | ax25: Fix issues of ax25_dev and net_device | expand |
> … 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
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
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); And then get rid of: > + /* Initialized the list for the first entry */ > + if (!ax25_dev_list.next) > + INIT_LIST_HEAD(&ax25_dev_list);
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;
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); }
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(-)