linux-kernel - Re: [PATCH] btrfs: use list_for_each_entry

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Message-ID: <CAG5DWog-Kom19-yB1TevGdzt+Xp9Jnsy3Yc9+ZfX2=G5zGwg2w@mail.gmail.com>
Date:	Sat, 31 Aug 2013 10:11:48 +0400
From:	Azat Khuzhin <a3at.mail@...il.com>
To:	miaox@...fujitsu.com
Cc:	linux-btrfs@...r.kernel.org, chris.mason@...ionio.com,
	open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] btrfs: use list_for_each_entry_safe() when delete items

On Tue, Jul 30, 2013 at 7:40 AM, Miao Xie <miaox@...fujitsu.com> wrote:
> On mon, 29 Jul 2013 11:48:32 +0400, Azat Khuzhin wrote:
>> On Sat, Jul 27, 2013 at 2:12 PM, Azat Khuzhin <a3at.mail@...il.com> 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 <a3at.mail@...il.com>
>>> ---
>>>  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 <miaox@...fujitsu.com>

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

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



-- 
Respectfully
Azat Khuzhin
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