Re: [PATCH v2 1/4] SUNRPC: release per-net clients lock before calling PipeFS dentries creation

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

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@xxxxxxxxxxxxx>

---
  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
--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html


[Linux Kernel Discussion]     [Ethernet Bridging]     [Linux Wireless Networking]     [Linux Bluetooth Networking]     [Linux Networking Users]     [VLAN]     [Git]     [IETF Annouce]     [Linux Assembly]     [Security]     [Bugtraq]     [Photo]     [Singles Social Networking]     [Yosemite Information]     [MIPS Linux]     [ARM Linux Kernel]     [ARM Linux]     [Linux Virtualization]     [Linux Security]     [Linux IDE]     [Linux RAID]     [Linux SCSI]     [Free Dating]

Add to Google Powered by Linux