On Mon, May 11, 2020 at 01:43:30PM +0000, Trond Myklebust wrote: > On Mon, 2020-05-11 at 09:16 -0400, J. Bruce Fields wrote: > > Thanks, applying.--b. > > > > You're applying? So should I remove it from the NFS client bugfixes? No. Sorry, I responded to the wrong email! --b. > > > On Mon, May 11, 2020 at 08:10:54AM -0400, Masayoshi Mizuma wrote: > > > 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 > -- > Trond Myklebust > Linux NFS client maintainer, Hammerspace > trond.myklebust@xxxxxxxxxxxxxxx > >
