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SubjectRe: [PATCH] fs: xfs: Fix a lock-twice and sleep-in-atomic bug in xfs_iget
On 06/05/2017 04:32 PM, Shan Hai wrote:
>
>
> On 2017年06月05日 16:17, Jia-Ju Bai wrote:
>> The driver may sleep under a read rcu lock, and function call path is:
>> xfs_iget (acquire the lock by rcu_read_lock)
>> "goto out_error_or_again" after xfs_iget_cache_hit
>> delay
>> schedule_timeout_uninterruptible --> may sleep
>> Meanwhile, the rcu_read_lock will be called twice in this situation.
>>
>> To fix it, the lock is released before "goto".
>>
>> Signed-off-by: Jia-Ju Bai <baijiaju1990@163.com>
>> ---
>> fs/xfs/xfs_icache.c | 4 +++-
>> 1 file changed, 3 insertions(+), 1 deletion(-)
>>
>> diff --git a/fs/xfs/xfs_icache.c b/fs/xfs/xfs_icache.c
>> index f61c84f8..c2a4722 100644
>> --- a/fs/xfs/xfs_icache.c
>> +++ b/fs/xfs/xfs_icache.c
>> @@ -600,8 +600,10 @@ struct xfs_inode *
>> if (ip) {
>> error = xfs_iget_cache_hit(pag, ip, ino, flags, lock_flags);
>> - if (error)
>> + if (error) {
>> + rcu_read_unlock();
>
> Seems you are going to double unlock by doing this, since it is
> unlocked in the xfs_iget_cache_hit.
>
> Thanks
> Shan Hai
>
>> goto out_error_or_again;
>> + }
>> } else {
>> rcu_read_unlock();
>> XFS_STATS_INC(mp, xs_ig_missed);
>
I think you are right. Please ignore my patch.

Thanks,
Jia-Ju Bai

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