On Fri, May 08, 2020 at 06:19:35PM -0400, J. Bruce Fields wrote:
> From: "J. Bruce Fields" <bfields@xxxxxxxxxx>
>
> We add the new state to the nfsi->open_states list, making it
> potentially visible to other threads, before we've finished initializing
> it.
>
> That wasn't a problem when all the readers were also taking the i_lock
> (as we do here), but since we switched to RCU, there's now a possibility
> that a reader could see the partially initialized state.
>
> Symptoms observed were a crash when another thread called
> nfs4_get_valid_delegation() on a NULL inode.
>
> Fixes: 9ae075fdd190 "NFSv4: Convert open state lookup to use RCU"
> Signed-off-by: J. Bruce Fields <bfields@xxxxxxxxxx>
> ---
> fs/nfs/nfs4state.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/fs/nfs/nfs4state.c b/fs/nfs/nfs4state.c
> index ac93715c05a4..a8dc25ce48bb 100644
> --- a/fs/nfs/nfs4state.c
> +++ b/fs/nfs/nfs4state.c
> @@ -734,9 +734,9 @@ nfs4_get_open_state(struct inode *inode, struct nfs4_state_owner *owner)
> state = new;
> state->owner = owner;
> atomic_inc(&owner->so_count);
> - list_add_rcu(&state->inode_states, &nfsi->open_states);
> ihold(inode);
> state->inode = inode;
> + list_add_rcu(&state->inode_states, &nfsi->open_states);
> spin_unlock(&inode->i_lock);
> /* Note: The reclaim code dictates that we add stateless
> * and read-only stateids to the end of the list */
> --
Thank you for posting the patch! It works for our box.
Please feel free to add:
Reviewed-by: Seiichi Ikarashi <s.ikarashi@xxxxxxxxxxx>
Tested-by: Daisuke Matsuda <matsuda-daisuke@xxxxxxxxxxx>
Tested-by: Masayoshi Mizuma <m.mizuma@xxxxxxxxxxxxxx>
Without the patch, the system which is a NFSv4 client has been
crashed randomly. The panic log is such as:
BUG: unable to handle page fault for address: ffffffffffffffb0
...
RIP: 0010:nfs4_get_valid_delegation+0x6/0x30 [nfsv4]
...
Call Trace:
nfs4_open_prepare+0x80/0x1c0 [nfsv4]
__rpc_execute+0x75/0x390 [sunrpc]
? finish_task_switch+0x75/0x260
rpc_async_schedule+0x29/0x40 [sunrpc]
process_one_work+0x1ad/0x370
worker_thread+0x30/0x390
? create_worker+0x1a0/0x1a0
kthread+0x10c/0x130
? kthread_park+0x80/0x80
ret_from_fork+0x22/0x30
After applied the patch, the panic is gone.
Thanks!
Masa
