On Nov 18, 2007 12:05 AM, Peter Zijlstra <[email protected]> wrote:
> I've been staring at this NFS code for a while an can't make any sense
> out of it. It seems to correctly initialize the waitqueue. So this would
> indicate corruption of some sort.
No, it does not "correctly" initialize the waitqueue. It doesn't even
try to initialize it.
I now found the guilty patch and what is wrong with it.
nfs-stop-sillyname-renames-and-unmounts-from-racing.patch adds:
@@ -110,8 +112,22 @@ struct nfs_server {
filesystem */
#endif
void (*destroy)(struct nfs_server *);
+
+ atomic_t active; /* Keep trace of any activity to this server */
+ wait_queue_head_t active_wq; /* Wait for any activity to stop */
and tries to initialize it:
@@ -593,6 +593,10 @@ static int nfs_init_server(struct nfs_server *server,
server->namelen = data->namlen;
/* Create a client RPC handle for the NFSv3 ACL management interface */
nfs_init_server_aclclient(server);
+
+ init_waitqueue_head(&server->active_wq);
+ atomic_set(&server->active, 0);
+
and then uses it via nfs_sb_active and nfs_sb_deactive:
@@ -29,6 +29,7 @@ struct nfs_unlinkdata {
static void
nfs_free_unlinkdata(struct nfs_unlinkdata *data)
{
+ nfs_sb_deactive(NFS_SERVER(data->dir));
iput(data->dir);
put_rpccred(data->cred);
kfree(data->args.name.name);
@@ -151,6 +152,7 @@ static int nfs_do_call_unlink(struct dentry
*parent, struct inode *dir, struct n
nfs_dec_sillycount(dir);
return 0;
}
+ nfs_sb_active(NFS_SERVER(dir));
data->args.fh = NFS_FH(dir);
nfs_fattr_init(&data->res.dir_attr);
But it does not notice this:
struct dentry_operations nfs_dentry_operations = {
.d_revalidate = nfs_lookup_revalidate,
.d_delete = nfs_dentry_delete,
.d_iput = nfs_dentry_iput,
};
struct dentry_operations nfs4_dentry_operations = {
.d_revalidate = nfs_open_revalidate,
.d_delete = nfs_dentry_delete,
.d_iput = nfs_dentry_iput,
};
NFSv2/3 and NFSv4 share the same dentry_iput and so share the same
unlink and sillyrename logic.
But they do not share nfs_init_server()!
I wonder why this doesn't blow up more violently, but only hangs...
But as I don't know if it is correct to add the workqueue
initialization to nfs4_init_server() or remove the nfs_sb_active /
nfs_sb_deactive for the NFSv4 case, I can't offer a patch to fix this.
Torsten
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