Message ID | 20120227155055.7941.18741.stgit@localhost6.localdomain6 |
---|---|
State | Not Applicable, archived |
Delegated to: | David Miller |
Headers | show |
27.02.2012 20:21, Myklebust, Trond пишет: > On Mon, 2012-02-27 at 19:50 +0400, Stanislav Kinsbursky wrote: >> Lockdep is sad otherwise, because inode mutex is taken on PipeFS dentry >> creation, which can be called on mount notification, where this per-net client >> lock is taken on clients list walk. >> >> Signed-off-by: Stanislav Kinsbursky<skinsbursky@parallels.com> >> >> --- >> net/sunrpc/clnt.c | 10 +++++++--- >> 1 files changed, 7 insertions(+), 3 deletions(-) >> >> diff --git a/net/sunrpc/clnt.c b/net/sunrpc/clnt.c >> index bb7ed2f3..ddb5741 100644 >> --- a/net/sunrpc/clnt.c >> +++ b/net/sunrpc/clnt.c >> @@ -84,7 +84,7 @@ static void rpc_register_client(struct rpc_clnt *clnt) >> struct sunrpc_net *sn = net_generic(clnt->cl_xprt->xprt_net, sunrpc_net_id); >> >> spin_lock(&sn->rpc_client_lock); >> - list_add(&clnt->cl_clients,&sn->all_clients); >> + list_add_tail(&clnt->cl_clients,&sn->all_clients); >> spin_unlock(&sn->rpc_client_lock); >> } >> >> @@ -208,15 +208,19 @@ static int rpc_pipefs_event(struct notifier_block *nb, unsigned long event, >> void *ptr) >> { >> struct super_block *sb = ptr; >> - struct rpc_clnt *clnt; >> + struct rpc_clnt *clnt, *tmp; >> int error = 0; >> struct sunrpc_net *sn = net_generic(sb->s_fs_info, sunrpc_net_id); >> >> spin_lock(&sn->rpc_client_lock); >> - list_for_each_entry(clnt,&sn->all_clients, cl_clients) { >> + list_for_each_entry_safe(clnt, tmp,&sn->all_clients, cl_clients) { >> + atomic_inc(&clnt->cl_count); >> + spin_unlock(&sn->rpc_client_lock); >> error = __rpc_pipefs_event(clnt, event, sb); >> + rpc_release_client(clnt); >> if (error) >> break; >> + spin_lock(&sn->rpc_client_lock); >> } >> spin_unlock(&sn->rpc_client_lock); >> return error; >> > > This won't be safe. Nothing guarantees that 'tmp' remains valid after > you drop the spin_lock. > > I think you rather need to add a check for whether clnt->cl_dentry is in > the right state (NULL if RPC_PIPEFS_UMOUNT or non-NULL if > RPC_PIPEFS_MOUNT) before deciding whether or not to atomic_inc() and > drop the lock, so that you can restart the loop after calling > __rpc_pipefs_event(). > Gmmm. Please, correct me, if I'm wrong, that you are proposing something like this: spin_lock(&sn->rpc_client_lock); again: list_for_each_entry(clnt,&sn->all_clients, cl_clients) { if ((event == RPC_PIPEFS_MOUNT) && clnt->cl_dentry) || (event == RPC_PIPEFS_UMOUNT) && !clnt->cl_dentry)) continue; atomic_inc(&clnt->cl_count); spin_unlock(&sn->rpc_client_lock); error = __rpc_pipefs_event(clnt, event, sb); rpc_release_client(clnt); spin_lock(&sn->rpc_client_lock); if (error) break; goto again; } spin_unlock(&sn->rpc_client_lock);
> Gmmm. > Please, correct me, if I'm wrong, that you are proposing > something like this: > > spin_lock(&sn->rpc_client_lock); > again: > list_for_each_entry(clnt,&sn->all_clients, cl_clients) { > if ((event == RPC_PIPEFS_MOUNT) && clnt->cl_dentry) || > (event == RPC_PIPEFS_UMOUNT) && !clnt->cl_dentry)) > continue; > atomic_inc(&clnt->cl_count); > spin_unlock(&sn->rpc_client_lock); > error = __rpc_pipefs_event(clnt, event, sb); > rpc_release_client(clnt); > spin_lock(&sn->rpc_client_lock); > if (error) > break; > goto again; > } > spin_unlock(&sn->rpc_client_lock); You might manage to request reference to the 'next' item while holding the lock. So maybe a loop that has: error = ... if (error) { rpc_release_client(clnt); break; } spin_lock(&sn->rpc_client_lock); next_clnt = list_next(clnt); if (next_clnt) atomic_inc(&next_clnt->cl_count); spin_unlock(&sn->rpc_client_lock); rpc_release_client(clnt); clnt = next_clnt; } while (clnt != NULL); David -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Mon, 2012-02-27 at 20:55 +0400, Stanislav Kinsbursky wrote: > 27.02.2012 20:21, Myklebust, Trond пишет: > > On Mon, 2012-02-27 at 19:50 +0400, Stanislav Kinsbursky wrote: > >> Lockdep is sad otherwise, because inode mutex is taken on PipeFS dentry > >> creation, which can be called on mount notification, where this per-net client > >> lock is taken on clients list walk. > >> > >> Signed-off-by: Stanislav Kinsbursky<skinsbursky@parallels.com> > >> > >> --- > >> net/sunrpc/clnt.c | 10 +++++++--- > >> 1 files changed, 7 insertions(+), 3 deletions(-) > >> > >> diff --git a/net/sunrpc/clnt.c b/net/sunrpc/clnt.c > >> index bb7ed2f3..ddb5741 100644 > >> --- a/net/sunrpc/clnt.c > >> +++ b/net/sunrpc/clnt.c > >> @@ -84,7 +84,7 @@ static void rpc_register_client(struct rpc_clnt *clnt) > >> struct sunrpc_net *sn = net_generic(clnt->cl_xprt->xprt_net, sunrpc_net_id); > >> > >> spin_lock(&sn->rpc_client_lock); > >> - list_add(&clnt->cl_clients,&sn->all_clients); > >> + list_add_tail(&clnt->cl_clients,&sn->all_clients); > >> spin_unlock(&sn->rpc_client_lock); > >> } > >> > >> @@ -208,15 +208,19 @@ static int rpc_pipefs_event(struct notifier_block *nb, unsigned long event, > >> void *ptr) > >> { > >> struct super_block *sb = ptr; > >> - struct rpc_clnt *clnt; > >> + struct rpc_clnt *clnt, *tmp; > >> int error = 0; > >> struct sunrpc_net *sn = net_generic(sb->s_fs_info, sunrpc_net_id); > >> > >> spin_lock(&sn->rpc_client_lock); > >> - list_for_each_entry(clnt,&sn->all_clients, cl_clients) { > >> + list_for_each_entry_safe(clnt, tmp,&sn->all_clients, cl_clients) { > >> + atomic_inc(&clnt->cl_count); > >> + spin_unlock(&sn->rpc_client_lock); > >> error = __rpc_pipefs_event(clnt, event, sb); > >> + rpc_release_client(clnt); > >> if (error) > >> break; > >> + spin_lock(&sn->rpc_client_lock); > >> } > >> spin_unlock(&sn->rpc_client_lock); > >> return error; > >> > > > > This won't be safe. Nothing guarantees that 'tmp' remains valid after > > you drop the spin_lock. > > > > I think you rather need to add a check for whether clnt->cl_dentry is in > > the right state (NULL if RPC_PIPEFS_UMOUNT or non-NULL if > > RPC_PIPEFS_MOUNT) before deciding whether or not to atomic_inc() and > > drop the lock, so that you can restart the loop after calling > > __rpc_pipefs_event(). > > > > Gmmm. > Please, correct me, if I'm wrong, that you are proposing something like this: > > spin_lock(&sn->rpc_client_lock); > again: > list_for_each_entry(clnt,&sn->all_clients, cl_clients) { > if ((event == RPC_PIPEFS_MOUNT) && clnt->cl_dentry) || > (event == RPC_PIPEFS_UMOUNT) && !clnt->cl_dentry)) > continue; > atomic_inc(&clnt->cl_count); > spin_unlock(&sn->rpc_client_lock); > error = __rpc_pipefs_event(clnt, event, sb); > rpc_release_client(clnt); > spin_lock(&sn->rpc_client_lock); > if (error) > break; > goto again; > } > spin_unlock(&sn->rpc_client_lock); Something along those lines, yes... Alternatively, you could do as David proposes, and grab a reference to the next rpc_client before calling rpc_release_client. Either works for me... -- Trond Myklebust Linux NFS client maintainer NetApp Trond.Myklebust@netapp.com www.netapp.com
diff --git a/net/sunrpc/clnt.c b/net/sunrpc/clnt.c index bb7ed2f3..ddb5741 100644 --- a/net/sunrpc/clnt.c +++ b/net/sunrpc/clnt.c @@ -84,7 +84,7 @@ static void rpc_register_client(struct rpc_clnt *clnt) struct sunrpc_net *sn = net_generic(clnt->cl_xprt->xprt_net, sunrpc_net_id); spin_lock(&sn->rpc_client_lock); - list_add(&clnt->cl_clients, &sn->all_clients); + list_add_tail(&clnt->cl_clients, &sn->all_clients); spin_unlock(&sn->rpc_client_lock); } @@ -208,15 +208,19 @@ static int rpc_pipefs_event(struct notifier_block *nb, unsigned long event, void *ptr) { struct super_block *sb = ptr; - struct rpc_clnt *clnt; + struct rpc_clnt *clnt, *tmp; int error = 0; struct sunrpc_net *sn = net_generic(sb->s_fs_info, sunrpc_net_id); spin_lock(&sn->rpc_client_lock); - list_for_each_entry(clnt, &sn->all_clients, cl_clients) { + list_for_each_entry_safe(clnt, tmp, &sn->all_clients, cl_clients) { + atomic_inc(&clnt->cl_count); + spin_unlock(&sn->rpc_client_lock); error = __rpc_pipefs_event(clnt, event, sb); + rpc_release_client(clnt); if (error) break; + spin_lock(&sn->rpc_client_lock); } spin_unlock(&sn->rpc_client_lock); return error;
Lockdep is sad otherwise, because inode mutex is taken on PipeFS dentry creation, which can be called on mount notification, where this per-net client lock is taken on clients list walk. Signed-off-by: Stanislav Kinsbursky <skinsbursky@parallels.com> --- net/sunrpc/clnt.c | 10 +++++++--- 1 files changed, 7 insertions(+), 3 deletions(-) -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html