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<skinsbur...@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);
--
Best regards,
Stanislav Kinsbursky
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