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SubjectRe: NFS client deadlock on SMP machines
From
>>>>> " " == Andrew Morton <andrewm@uow.edu.au> writes:

> There appear to be two places where the NFS client code can
> deadlock:

> nfs_reqlist_init() {
> spin_lock(&nfs_flushd_lock);
> rpc_new_task->
> rpc_allocate->
> -> kmalloc(GFP_RPC) (__GFP_WAIT is true)


> inode_remove_flushd() {
> spin_lock(&nfs_flushd_lock);
> iput(inode)->
> nfs_delete_inode->
> delete_inode->
> wait_on_inode
> truncate_inode_pages->
> truncate_list_pages->
> wait_on_page

> The latter is most likely the problem. Here's a patch - please
> test. The inode_remove_flush() change is correct. Not so sure
> about the nfs_reqlist_init() change.


Doh. You're quite right on both accounts. I made a small modification
to your patch for the rpc_new_task() problem (you forgot to release
the RPC task if it's not used).

Linus, please apply for 2.4.1...

Cheers,
Trond

--- linux-2.4.0/fs/nfs/flushd.c.orig Wed Jun 21 16:25:17 2000
+++ linux-2.4.0/fs/nfs/flushd.c Wed Jan 10 10:44:08 2001
@@ -71,18 +71,17 @@
int status = 0;

dprintk("NFS: writecache_init\n");
+
+ /* Create the RPC task */
+ if (!(task = rpc_new_task(server->client, NULL, RPC_TASK_ASYNC)))
+ return -ENOMEM;
+
spin_lock(&nfs_flushd_lock);
cache = server->rw_requests;

if (cache->task)
goto out_unlock;

- /* Create the RPC task */
- status = -ENOMEM;
- task = rpc_new_task(server->client, NULL, RPC_TASK_ASYNC);
- if (!task)
- goto out_unlock;
-
task->tk_calldata = server;

cache->task = task;
@@ -99,6 +98,7 @@
return 0;
out_unlock:
spin_unlock(&nfs_flushd_lock);
+ rpc_release_task(task);
return status;
}

@@ -195,7 +195,9 @@
if (*q) {
*q = inode->u.nfs_i.hash_next;
NFS_FLAGS(inode) &= ~NFS_INO_FLUSH;
+ spin_unlock(&nfs_flushd_lock);
iput(inode);
+ return;
}
out:
spin_unlock(&nfs_flushd_lock);
-
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