On Fri, 30 Aug 2024, Mike Snitzer wrote:
> On Fri, Aug 30, 2024 at 02:36:13PM +1000, NeilBrown wrote:
> > On Fri, 30 Aug 2024, Jeff Layton wrote:
> > > Have a pointer to a struct nfsd_localio_ops or something in the
> > > nfs_common module. That's initially set to NULL. Then, have a static
> > > structure of that type in nfsd.ko, and have its __init routine set the
> > > pointer in nfs_common to point to the right structure. The __exit
> > > routine will later set it to NULL.
> > >
> > > > I really don't want all calls in NFS client (or nfs_common) to have to
> > > > first check if nfs_common's 'nfs_to' ops structure is NULL or not.
> > >
> > > Neil seems to think that's not necessary:
> > >
> > > "If nfs/localio holds an auth_domain, then it implicitly holds a
> > > reference to the nfsd module and the functions cannot disappear."
> >
> > On reflection that isn't quite right, but it is the sort of approach
> > that I think we need to take.
> > There are several things that the NFS client needs to hold one to.
> >
> > 1/ It needs a reference to the nfsd module (or symbols in the module).
> > I think this can be held long term but we need a clear mechanism for
> > it to be dropped.
> > 2/ It needs a reference to the nfsd_serv which it gets through the
> > 'struct net' pointer. I've posted patches to handle that better.
> > 3/ It needs a reference to an auth_domain. This can safely be a long
> > term reference. It can already be invalidated and the code to free
> > it is in sunrpc which nfs already pins. Any delay in freeing it only
> > wastes memory (not much), it doesn't impact anything else.
> > 4/ It needs a reference to the nfsd_file and/or file. This is currently
> > done only while the ref to the nfsd_serv is held, so I think there is
> > no problem there.
> >
> > So possibly we could take a reference to the nfsd module whenever we
> > store a net in nfs_uuid. and drop the ref whenever we clear that.
> >
> > That means we cannot call nfsd_open_local_fh() without first getting a
> > ref on the nfsd_serv which my latest code doesn't do. That is easily
> > fixed. I'll send a patch for consideration...
>
> I already implemented 2 different versions today, meant for v15.
>
> First is a relaxed version of the v14 code (less code, only using
> symbol_request on nfsd_open_local_fh.
>
> Second is much more relaxed, because it leverages your original
> assumption that the auth_domain ref sufficient.
>
> I'll reply twice to this mail with each each respective patch.
Thanks... Unfortunately auth_domain isn't sufficient.
This is my version. It should folded back into one or more earlier
patches. I think it is simpler.
It is against your v15 but with my 6 nfs_uuid patches replaces your
equivalents.
Thanks,
NeilBrown
diff --git a/fs/nfs/localio.c b/fs/nfs/localio.c
index 55622084d5c2..18b7554ec516 100644
--- a/fs/nfs/localio.c
+++ b/fs/nfs/localio.c
@@ -235,8 +235,8 @@ nfs_local_open_fh(struct nfs_client *clp, const struct cred *cred,
if (mode & ~(FMODE_READ | FMODE_WRITE))
return NULL;
- localio = nfs_to.nfsd_open_local_fh(&clp->cl_uuid,
- clp->cl_rpcclient, cred, fh, mode);
+ localio = nfs_open_local_fh(&clp->cl_uuid,
+ clp->cl_rpcclient, cred, fh, mode);
if (IS_ERR(localio)) {
status = PTR_ERR(localio);
trace_nfs_local_open_fh(fh, mode, status);
diff --git a/fs/nfs_common/nfslocalio.c b/fs/nfs_common/nfslocalio.c
index 8545ee75f756..cd9733eb3e4f 100644
--- a/fs/nfs_common/nfslocalio.c
+++ b/fs/nfs_common/nfslocalio.c
@@ -54,8 +54,11 @@ static nfs_uuid_t * nfs_uuid_lookup(const uuid_t *uuid)
return NULL;
}
+struct module *nfsd_mod;
+
void nfs_uuid_is_local(const uuid_t *uuid, struct list_head *list,
- struct net *net, struct auth_domain *dom)
+ struct net *net, struct auth_domain *dom,
+ struct module *mod)
{
nfs_uuid_t *nfs_uuid;
@@ -70,6 +73,9 @@ void nfs_uuid_is_local(const uuid_t *uuid, struct list_head *list,
*/
list_move(&nfs_uuid->list, list);
nfs_uuid->net = net;
+
+ __module_get(mod);
+ nfsd_mod = mod;
}
spin_unlock(&nfs_uuid_lock);
}
@@ -77,8 +83,10 @@ EXPORT_SYMBOL_GPL(nfs_uuid_is_local);
static void nfs_uuid_put_locked(nfs_uuid_t *nfs_uuid)
{
- if (nfs_uuid->net)
+ if (nfs_uuid->net) {
put_net(nfs_uuid->net);
+ module_put(nfsd_mod);
+ }
nfs_uuid->net = NULL;
if (nfs_uuid->dom)
auth_domain_put(nfs_uuid->dom);
@@ -107,6 +115,26 @@ void nfs_uuid_invalidate_one_client(nfs_uuid_t *nfs_uuid)
}
EXPORT_SYMBOL_GPL(nfs_uuid_invalidate_one_client);
+struct nfs_localio_ctx *nfs_open_local_fh(nfs_uuid_t *uuid,
+ struct rpc_clnt *rpc_clnt, const struct cred *cred,
+ const struct nfs_fh *nfs_fh, const fmode_t fmode)
+{
+ struct nfs_localio_ctx *localio;
+
+ rcu_read_lock();
+ if (!READ_ONCE(uuid->net)) {
+ rcu_read_unlock();
+ return ERR_PTR(-ENXIO);
+ }
+ localio = nfs_to.nfsd_open_local_fh(uuid, rpc_clnt, cred,
+ nfs_fh, fmode);
+ rcu_read_unlock();
+ if (IS_ERR(localio))
+ nfs_to.nfsd_serv_put(localio->nn);
+ return localio;
+}
+EXPORT_SYMBOL_GPL(nfs_open_local_fh);
+
/*
* The nfs localio code needs to call into nfsd using various symbols (below),
* but cannot be statically linked, because that will make the nfs module
@@ -135,7 +163,8 @@ static void put_##NFSD_SYMBOL(void) \
/* The nfs localio code needs to call into nfsd to map filehandle -> struct nfsd_file */
extern struct nfs_localio_ctx *
nfsd_open_local_fh(nfs_uuid_t *, struct rpc_clnt *,
- const struct cred *, const struct nfs_fh *, const fmode_t);
+ const struct cred *, const struct nfs_fh *, const fmode_t)
+ __must_hold(rcu);
DEFINE_NFS_TO_NFSD_SYMBOL(nfsd_open_local_fh);
/* The nfs localio code needs to call into nfsd to acquire the nfsd_file */
diff --git a/fs/nfsd/localio.c b/fs/nfsd/localio.c
index 491bf5017d34..d50e54406914 100644
--- a/fs/nfsd/localio.c
+++ b/fs/nfsd/localio.c
@@ -45,6 +45,7 @@ struct nfs_localio_ctx *
nfsd_open_local_fh(nfs_uuid_t *uuid,
struct rpc_clnt *rpc_clnt, const struct cred *cred,
const struct nfs_fh *nfs_fh, const fmode_t fmode)
+ __must_hold(rcu)
{
int mayflags = NFSD_MAY_LOCALIO;
int status = 0;
@@ -58,10 +59,6 @@ nfsd_open_local_fh(nfs_uuid_t *uuid,
if (nfs_fh->size > NFS4_FHSIZE)
return ERR_PTR(-EINVAL);
- localio = nfs_localio_ctx_alloc();
- if (!localio)
- return ERR_PTR(-ENOMEM);
-
/*
* Not running in nfsd context, so must safely get reference on nfsd_serv.
* But the server may already be shutting down, if so disallow new localio.
@@ -69,17 +66,22 @@ nfsd_open_local_fh(nfs_uuid_t *uuid,
* uuid->net is not NULL, then nfsd_serv_try_get() is safe and if that succeeds
* we will have an implied reference to the net.
*/
- rcu_read_lock();
net = READ_ONCE(uuid->net);
if (net)
nn = net_generic(net, nfsd_net_id);
- if (unlikely(!nn || !nfsd_serv_try_get(nn))) {
- rcu_read_unlock();
- status = -ENXIO;
- goto out_nfsd_serv;
- }
+ if (unlikely(!nn || !nfsd_serv_try_get(nn)))
+ return -ENXIO;
+
+ /* Drop the rcu lock for alloc and nfsd_file_acquire_local() */
rcu_read_unlock();
+ localio = nfs_localio_ctx_alloc();
+ if (!localio) {
+ localio = ERR_PTR(-ENOMEM);
+ nfsd_serv_put(nn);
+ goto out_localio;
+ }
+
/* nfs_fh -> svc_fh */
fh_init(&fh, NFS4_FHSIZE);
fh.fh_handle.fh_size = nfs_fh->size;
@@ -104,11 +106,13 @@ nfsd_open_local_fh(nfs_uuid_t *uuid,
fh_put(&fh);
if (rq_cred.cr_group_info)
put_group_info(rq_cred.cr_group_info);
-out_nfsd_serv:
+
if (status) {
nfs_localio_ctx_free(localio);
- return ERR_PTR(status);
+ localio = ERR_PTR(status);
}
+out_localio:
+ rcu_read_lock();
return localio;
}
EXPORT_SYMBOL_GPL(nfsd_open_local_fh);
@@ -136,7 +140,7 @@ static __be32 localio_proc_uuid_is_local(struct svc_rqst *rqstp)
struct nfsd_net *nn = net_generic(net, nfsd_net_id);
nfs_uuid_is_local(&argp->uuid, &nn->local_clients,
- net, rqstp->rq_client);
+ net, rqstp->rq_client, THIS_MODULE);
return rpc_success;
}
diff --git a/fs/nfsd/vfs.h b/fs/nfsd/vfs.h
index 2ecceb8b9d3d..c73633120997 100644
--- a/fs/nfsd/vfs.h
+++ b/fs/nfsd/vfs.h
@@ -164,7 +164,8 @@ void nfsd_filp_close(struct file *fp);
struct nfs_localio_ctx *
nfsd_open_local_fh(nfs_uuid_t *,
struct rpc_clnt *, const struct cred *,
- const struct nfs_fh *, const fmode_t);
+ const struct nfs_fh *, const fmode_t)
+ __must_hold(rcu);
static inline int fh_want_write(struct svc_fh *fh)
{
diff --git a/include/linux/nfslocalio.h b/include/linux/nfslocalio.h
index e196f716a2f5..303e82e75b9e 100644
--- a/include/linux/nfslocalio.h
+++ b/include/linux/nfslocalio.h
@@ -29,7 +29,7 @@ typedef struct {
void nfs_uuid_begin(nfs_uuid_t *);
void nfs_uuid_end(nfs_uuid_t *);
void nfs_uuid_is_local(const uuid_t *, struct list_head *,
- struct net *, struct auth_domain *);
+ struct net *, struct auth_domain *, struct module *);
void nfs_uuid_invalidate_clients(struct list_head *list);
void nfs_uuid_invalidate_one_client(nfs_uuid_t *nfs_uuid);
@@ -69,4 +69,8 @@ void put_nfs_to_nfsd_symbols(void);
struct nfs_localio_ctx *nfs_localio_ctx_alloc(void);
void nfs_localio_ctx_free(struct nfs_localio_ctx *);
+struct nfs_localio_ctx *nfs_open_local_fh(nfs_uuid_t *uuid,
+ struct rpc_clnt *rpc_clnt, const struct cred *cred,
+ const struct nfs_fh *nfs_fh, const fmode_t fmode);
+
#endif /* __LINUX_NFSLOCALIO_H */
