[PATCH] nfs: add minor version to nfs_server_key for fscache

[Scott Mayhew <smayhew@redhat.com>]

If the same NFS filesystem is mounted multiple times with "-o fsc" and
different NFS versions, the following oops can occur.

Fix it by adding the minor version to the struct nfs_server_key.

Note this requires waiting to call nfs_fscache_get_client_cookie()
until after the nfs_client has been initialized.

kernel BUG at fs/cachefiles/namei.c:194!
invalid opcode: 0000 [#1] SMP PTI
Modules linked in: ...
CPU: 1 PID: 6 Comm: kworker/u4:0 Kdump: loaded Not tainted 4.17.3-200.fc28.x86_64 #1
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-2.fc27 04/01/2014
Workqueue: fscache_object fscache_object_work_func [fscache]
RIP: 0010:cachefiles_walk_to_object.cold.16+0x124/0x18c [cachefiles]
RSP: 0000:ffffa37f40347d50 EFLAGS: 00010246
RAX: 0000000000000001 RBX: ffff9327f3e94300 RCX: 0000000000000006
RDX: 0000000000000000 RSI: 0000000000000092 RDI: ffff9327ffd16930
RBP: ffff9327f3e94000 R08: 0000000000000000 R09: 000000000000026f
R10: 0000000000000000 R11: 0000000000000001 R12: ffff9327faa59840
R13: ffff9327faa59840 R14: ffff9327f3e94440 R15: ffff9327f3e94ec0
FS:  0000000000000000(0000) GS:ffff9327ffd00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f63f1db28a0 CR3: 000000002020a001 CR4: 00000000003606e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 ? __queue_work+0x103/0x3e0
 ? __switch_to_asm+0x34/0x70
 cachefiles_lookup_object+0x4b/0xa0 [cachefiles]
 fscache_look_up_object+0x9c/0x110 [fscache]
 ? fscache_parent_ready+0x2a/0x50 [fscache]
 fscache_object_work_func+0x74/0x2b0 [fscache]
 process_one_work+0x187/0x340
 worker_thread+0x2e/0x380
 ? pwq_unbound_release_workfn+0xd0/0xd0
 kthread+0x112/0x130
 ? kthread_create_worker_on_cpu+0x70/0x70
 ret_from_fork+0x35/0x40
Code: ...
RIP: cachefiles_walk_to_object.cold.16+0x124/0x18c [cachefiles] RSP: ffffa37f40347d50

Signed-off-by: Scott Mayhew <smayhew@redhat.com>
---
 fs/nfs/client.c  | 8 +++++---
 fs/nfs/fscache.c | 2 ++
 2 files changed, 7 insertions(+), 3 deletions(-)

diff --git a/fs/nfs/client.c b/fs/nfs/client.c
index 377a61654a88..bfd1b4e2852b 100644
--- a/fs/nfs/client.c
+++ b/fs/nfs/client.c
@@ -185,7 +185,6 @@ struct nfs_client *nfs_alloc_client(const struct nfs_client_initdata *cl_init)
 	cred = rpc_lookup_machine_cred("*");
 	if (!IS_ERR(cred))
 		clp->cl_machine_cred = cred;
-	nfs_fscache_get_client_cookie(clp);
 
 	return clp;
 
@@ -397,7 +396,7 @@ nfs_found_client(const struct nfs_client_initdata *cl_init,
  */
 struct nfs_client *nfs_get_client(const struct nfs_client_initdata *cl_init)
 {
-	struct nfs_client *clp, *new = NULL;
+	struct nfs_client *clp, *ret, *new = NULL;
 	struct nfs_net *nn = net_generic(cl_init->net, nfs_net_id);
 	const struct nfs_rpc_ops *rpc_ops = cl_init->nfs_mod->rpc_ops;
 
@@ -422,7 +421,10 @@ struct nfs_client *nfs_get_client(const struct nfs_client_initdata *cl_init)
 					&nn->nfs_client_list);
 			spin_unlock(&nn->nfs_client_lock);
 			new->cl_flags = cl_init->init_flags;
-			return rpc_ops->init_client(new, cl_init);
+			ret = rpc_ops->init_client(new, cl_init);
+			if (!IS_ERR(ret))
+				nfs_fscache_get_client_cookie(new);
+			return ret;
 		}
 
 		spin_unlock(&nn->nfs_client_lock);
diff --git a/fs/nfs/fscache.c b/fs/nfs/fscache.c
index 4dc887813c71..c32146319944 100644
--- a/fs/nfs/fscache.c
+++ b/fs/nfs/fscache.c
@@ -35,6 +35,7 @@ static DEFINE_SPINLOCK(nfs_fscache_keys_lock);
 struct nfs_server_key {
 	struct {
 		uint16_t	nfsversion;		/* NFS protocol version */
+		uint16_t	minorversion;		/* NFSv4 minor version */
 		uint16_t	family;			/* address family */
 		__be16		port;			/* IP port */
 	} hdr;
@@ -59,6 +60,7 @@ void nfs_fscache_get_client_cookie(struct nfs_client *clp)
 
 	memset(&key, 0, sizeof(key));
 	key.hdr.nfsversion = clp->rpc_ops->version;
+	key.hdr.minorversion = clp->cl_minorversion;
 	key.hdr.family = clp->cl_addr.ss_family;
 
 	switch (clp->cl_addr.ss_family) {
-- 
2.14.4