On Oct 28, 2013, at 2:45 PM, Myklebust, Trond <Trond.Myklebust@xxxxxxxxxx> wrote:
> On Mon, 2013-10-21 at 13:10 -0400, Weston Andros Adamson wrote:
>> Use atomic_inc_not_zero() to avoid referencing a state that is currently
>> being freed.
>>
>> Signed-off-by: Weston Andros Adamson <dros@xxxxxxxxxx>
>> ---
>> fs/nfs/nfs4proc.c | 8 ++++++--
>> fs/nfs/nfs4state.c | 3 ++-
>> 2 files changed, 8 insertions(+), 3 deletions(-)
>>
>> diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
>> index a3b78df..005543d 100644
>> --- a/fs/nfs/nfs4proc.c
>> +++ b/fs/nfs/nfs4proc.c
>> @@ -1275,7 +1275,8 @@ static struct nfs4_state *nfs4_try_open_cached(struct nfs4_opendata *opendata)
>> out:
>> return ERR_PTR(ret);
>> out_return_state:
>> - atomic_inc(&state->count);
>> + if (!atomic_inc_not_zero(&state->count))
>> + return ERR_PTR(-EINVAL);
>> return state;
>> }
>>
>> @@ -1429,7 +1430,10 @@ static struct nfs4_opendata *nfs4_open_recoverdata_alloc(struct nfs_open_context
>> if (opendata == NULL)
>> return ERR_PTR(-ENOMEM);
>> opendata->state = state;
>> - atomic_inc(&state->count);
>> + if (!atomic_inc_not_zero(&state->count)) {
>> + nfs4_opendata_put(opendata);
>> + return ERR_PTR(-EINVAL);
>> + }
>> return opendata;
>> }
>>
>> diff --git a/fs/nfs/nfs4state.c b/fs/nfs/nfs4state.c
>> index cc14cbb..1c71907 100644
>> --- a/fs/nfs/nfs4state.c
>> +++ b/fs/nfs/nfs4state.c
>> @@ -1416,7 +1416,8 @@ restart:
>> continue;
>> if (state->state == 0)
>> continue;
>> - atomic_inc(&state->count);
>> + if (!atomic_inc_not_zero(&state->count))
>> + continue;
>> spin_unlock(&sp->so_lock);
>> status = ops->recover_open(sp, state);
>> if (status >= 0) {
>
> Is this patch needed? We should already be holding a reference to the
> open_context, so AFAICS we know that the state->count is non-zero.
I have no evidence that this is needed, it was purely for consistency. Feel free to drop this patch.
-dros
>
> Cheers
> Trond
> --
> Trond Myklebust
> Linux NFS client maintainer
>
> NetApp
> Trond.Myklebust@xxxxxxxxxx
> www.netapp.com
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