2013-07-27 10:13:07

by Azat Khuzhin

Subject: [PATCH] btrfs: use list_for_each_entry_safe() when delete items

Replace list_for_each_entry() by list_for_each_entry_safe() in
__btrfs_close_devices()

There is another place that delete items lock_stripe_add(), but there we
don't need safe version, because after deleting we exit from loop.

Signed-off-by: Azat Khuzhin <[email protected]>
---
fs/btrfs/volumes.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 78b8717..1d1b595 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -616,13 +616,13 @@ static void free_device(struct rcu_head *head)

static int __btrfs_close_devices(struct btrfs_fs_devices *fs_devices)
{
- struct btrfs_device *device;
+ struct btrfs_device *device, *next;

if (--fs_devices->opened > 0)
return 0;

mutex_lock(&fs_devices->device_list_mutex);
- list_for_each_entry(device, &fs_devices->devices, dev_list) {
+ list_for_each_entry_safe(device, next, &fs_devices->devices, dev_list) {
struct btrfs_device *new_device;
struct rcu_string *name;

--
1.7.10.4

2013-07-29 07:48:34

by Azat Khuzhin

Subject: Re: [PATCH] btrfs: use list_for_each_entry_safe() when delete items

On Sat, Jul 27, 2013 at 2:12 PM, Azat Khuzhin <[email protected]> wrote:
> Replace list_for_each_entry() by list_for_each_entry_safe() in
> __btrfs_close_devices()
>
> There is another place that delete items lock_stripe_add(), but there we
> don't need safe version, because after deleting we exit from loop.
>
> Signed-off-by: Azat Khuzhin <[email protected]>
> ---
> fs/btrfs/volumes.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
> index 78b8717..1d1b595 100644
> --- a/fs/btrfs/volumes.c
> +++ b/fs/btrfs/volumes.c
> @@ -616,13 +616,13 @@ static void free_device(struct rcu_head *head)
>
> static int __btrfs_close_devices(struct btrfs_fs_devices *fs_devices)
> {
> - struct btrfs_device *device;
> + struct btrfs_device *device, *next;
>
> if (--fs_devices->opened > 0)
> return 0;
>
> mutex_lock(&fs_devices->device_list_mutex);
> - list_for_each_entry(device, &fs_devices->devices, dev_list) {
> + list_for_each_entry_safe(device, next, &fs_devices->devices, dev_list) {
> struct btrfs_device *new_device;
> struct rcu_string *name;

There is "kfree(device);" at the end of loop, maybe there must "goto
again;" after it?
(instead of this patch)

>
> --
> 1.7.10.4
>



--
Respectfully
Azat Khuzhin

2013-07-30 03:39:57

by Miao Xie

Subject: Re: [PATCH] btrfs: use list_for_each_entry_safe() when delete items

On mon, 29 Jul 2013 11:48:32 +0400, Azat Khuzhin wrote:
> On Sat, Jul 27, 2013 at 2:12 PM, Azat Khuzhin <[email protected]> wrote:
>> Replace list_for_each_entry() by list_for_each_entry_safe() in
>> __btrfs_close_devices()
>>
>> There is another place that delete items lock_stripe_add(), but there we
>> don't need safe version, because after deleting we exit from loop.
>>
>> Signed-off-by: Azat Khuzhin <[email protected]>
>> ---
>> fs/btrfs/volumes.c | 4 ++--
>> 1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
>> index 78b8717..1d1b595 100644
>> --- a/fs/btrfs/volumes.c
>> +++ b/fs/btrfs/volumes.c
>> @@ -616,13 +616,13 @@ static void free_device(struct rcu_head *head)
>>
>> static int __btrfs_close_devices(struct btrfs_fs_devices *fs_devices)
>> {
>> - struct btrfs_device *device;
>> + struct btrfs_device *device, *next;
>>
>> if (--fs_devices->opened > 0)
>> return 0;
>>
>> mutex_lock(&fs_devices->device_list_mutex);
>> - list_for_each_entry(device, &fs_devices->devices, dev_list) {
>> + list_for_each_entry_safe(device, next, &fs_devices->devices, dev_list) {
>> struct btrfs_device *new_device;
>> struct rcu_string *name;
>
> There is "kfree(device);" at the end of loop, maybe there must "goto
> again;" after it?
> (instead of this patch)

Your fix is right, we needn't search from the head once again.

The other fix way is:
call_rcu(&device->rcu, free_device);
+ device = new_device;
}
but from the viewpoint of the readability, this way is not so good.

Reviewed-by: Miao Xie <[email protected]>

>
>>
>> --
>> 1.7.10.4
>>
>
>
>

2013-08-31 06:11:51

by Azat Khuzhin

Subject: Re: [PATCH] btrfs: use list_for_each_entry_safe() when delete items

On Tue, Jul 30, 2013 at 7:40 AM, Miao Xie <[email protected]> wrote:
> On mon, 29 Jul 2013 11:48:32 +0400, Azat Khuzhin wrote:
>> On Sat, Jul 27, 2013 at 2:12 PM, Azat Khuzhin <[email protected]> wrote:
>>> Replace list_for_each_entry() by list_for_each_entry_safe() in
>>> __btrfs_close_devices()
>>>
>>> There is another place that delete items lock_stripe_add(), but there we
>>> don't need safe version, because after deleting we exit from loop.
>>>
>>> Signed-off-by: Azat Khuzhin <[email protected]>
>>> ---
>>> fs/btrfs/volumes.c | 4 ++--
>>> 1 file changed, 2 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
>>> index 78b8717..1d1b595 100644
>>> --- a/fs/btrfs/volumes.c
>>> +++ b/fs/btrfs/volumes.c
>>> @@ -616,13 +616,13 @@ static void free_device(struct rcu_head *head)
>>>
>>> static int __btrfs_close_devices(struct btrfs_fs_devices *fs_devices)
>>> {
>>> - struct btrfs_device *device;
>>> + struct btrfs_device *device, *next;
>>>
>>> if (--fs_devices->opened > 0)
>>> return 0;
>>>
>>> mutex_lock(&fs_devices->device_list_mutex);
>>> - list_for_each_entry(device, &fs_devices->devices, dev_list) {
>>> + list_for_each_entry_safe(device, next, &fs_devices->devices, dev_list) {
>>> struct btrfs_device *new_device;
>>> struct rcu_string *name;
>>
>> There is "kfree(device);" at the end of loop, maybe there must "goto
>> again;" after it?
>> (instead of this patch)

Ugh. I was looking into another function!

>
> Your fix is right, we needn't search from the head once again.
>
> The other fix way is:
> call_rcu(&device->rcu, free_device);
> + device = new_device;
> }
> but from the viewpoint of the readability, this way is not so good.
>
> Reviewed-by: Miao Xie <[email protected]>

Thanks!
Miao, should I resend patch with you reviewed-by?

>
>>
>>>
>>> --
>>> 1.7.10.4
>>>
>>
>>
>>
>



--
Respectfully
Azat Khuzhin