[linux-cifs-client] [PATCH] Cannot allocate memory

[Pavel Shilovsky]

Hello!

This patch resolves problem "Cannot allocate memory" during loading 
module when we do unload/load quickly. During unloading the 
cifs_demultiplex_thread doesn't have enough time for clearing cache and 
kmem_cache_destroy fails. Then during loading module it fails with 
kmem_cache_create: duplicate cache cifs_request.

This script can show this bug:

rmmod cifs

for i in `seq 1 20`;
do {
        echo "trying to mount " $i
        insmod ./cifs.ko
        cifsmount [имя шары] [путь] -onoperm
        umount [путь]
        rmmod cifs
};
done



And it fails on 2nd iteration.

My patch fixes it.

diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h
index 1ae6314..18ba45a 100644
--- a/fs/cifs/cifsglob.h
+++ b/fs/cifs/cifsglob.h
@@ -176,6 +176,7 @@ struct TCP_Server_Info {
        struct mac_key mac_signing_key;
        char ntlmv2_hash[16];
        unsigned long lstrp; /* when we got last response from this 
server */
+       int running;
 };

 /*
diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index f254235..39daaf2 100644
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -347,6 +347,7 @@ cifs_demultiplex_thread(struct TCP_Server_Info *server)
        bool isMultiRsp;
        int reconnect;

+       server->running = 1;
        current->flags |= PF_MEMALLOC;
        cFYI(1, ("Demultiplex PID: %d", task_pid_nr(current)));

@@ -758,6 +759,8 @@ multi_t2_fnd:

        kfree(server->hostname);
        task_to_wake = xchg(&server->tsk, NULL);
+       server->running = 0;
+       msleep(20);
        kfree(server);

        length = atomic_dec_return(&tcpSesAllocCount);
@@ -1408,6 +1411,9 @@ cifs_put_tcp_session(struct TCP_Server_Info *server)
        task = xchg(&server->tsk, NULL);
        if (task)
                force_sig(SIGKILL, task);
+
+       while(server->running == 1)
+               msleep(10);
 }

 static struct cifsSesInfo *


--
Best regards,
Pavel Shilovsky.