On 2019/5/17 5:22 PM, Joseph Qi wrote:
> Hi Yihao,
>
> On 19/5/13 14:57, Yihao Wu wrote:
>> Commit b7dbcc0e433f "NFSv4.1: Fix a race where CB_NOTIFY_LOCK fails to wake a waiter"
>> found this bug. However it didn't fix it.
>>
>> This commit replaces schedule_timeout() with wait_woken() and
>> default_wake_function() with woken_wake_function() in function
>> nfs4_retry_setlk() and nfs4_wake_lock_waiter(). wait_woken() uses
>> memory barriers in its implementation to avoid potential race condition
>> when putting a process into sleeping state and then waking it up.
>>
>> Fixes: a1d617d8f134 ("nfs: allow blocking locks to be awoken by lock callbacks")
>> Cc: stable@xxxxxxxxxxxxxxx #4.9+
>> Signed-off-by: Yihao Wu <wuyihao@xxxxxxxxxxxxxxxxx>
>> ---
>> fs/nfs/nfs4proc.c | 23 +++++++----------------
>> 1 file changed, 7 insertions(+), 16 deletions(-)
>>
>> diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
>> index c29cbef..f9ed6b5 100644
>> --- a/fs/nfs/nfs4proc.c
>> +++ b/fs/nfs/nfs4proc.c
>> @@ -6932,7 +6932,6 @@ struct nfs4_lock_waiter {
>> struct task_struct *task;
>> struct inode *inode;
>> struct nfs_lowner *owner;
>> - bool notified;
>> };
>>
>> static int
>> @@ -6954,13 +6953,13 @@ struct nfs4_lock_waiter {
>> /* Make sure it's for the right inode */
>> if (nfs_compare_fh(NFS_FH(waiter->inode), &cbnl->cbnl_fh))
>> return 0;
>> -
>> - waiter->notified = true;
>> }
>>
>> /* override "private" so we can use default_wake_function */
>> wait->private = waiter->task;
>> - ret = autoremove_wake_function(wait, mode, flags, key);
>> + ret = woken_wake_function(wait, mode, flags, key);
>> + if (ret)
>> + list_del_init(&wait->entry);
>> wait->private = waiter;
>> return ret;
>> }
>> @@ -6979,8 +6978,7 @@ struct nfs4_lock_waiter {
>> .s_dev = server->s_dev };
>> struct nfs4_lock_waiter waiter = { .task = current,
>> .inode = state->inode,
>> - .owner = &owner,
>> - .notified = false };
>> + .owner = &owner};
>> wait_queue_entry_t wait;
>>
>> /* Don't bother with waitqueue if we don't expect a callback */
>> @@ -6993,21 +6991,14 @@ struct nfs4_lock_waiter {
>> add_wait_queue(q, &wait);
>>
>> while(!signalled()) {
>> - waiter.notified = false;
>> status = nfs4_proc_setlk(state, cmd, request);
>> if ((status != -EAGAIN) || IS_SETLK(cmd))
>> break;
>>
>> status = -ERESTARTSYS;
>> - spin_lock_irqsave(&q->lock, flags);
>> - if (waiter.notified) {
>> - spin_unlock_irqrestore(&q->lock, flags);
>> - continue;
>> - }
>> - set_current_state(TASK_INTERRUPTIBLE);
>> - spin_unlock_irqrestore(&q->lock, flags);
>> -
>> - freezable_schedule_timeout(NFS4_LOCK_MAXTIMEOUT);
>> + freezer_do_not_count();
>> + wait_woken(&wait, TASK_INTERRUPTIBLE, NFS4_LOCK_MAXTIMEOUT);
>> + freezer_count();
>
> Since now variable 'flags' is not used anymore, we have to delete it as well.
> Otherwise there is a compile warning “unused variable ‘flags’”.
>
> Thanks,
> Joseph
Thank you Joseph. I'll remove unused 'flags' in PATCH v3.
Thanks,
Yihao Wu
>
>> }
>>
>> finish_wait(q, &wait);
>>
