[PATCH v7 16/20] nfsd: prepare to use SRCU to dereference nn->nfsd_serv

Mike Snitzer
2024-06-24T16:28:05Z

The next commit switches the nfsd_serv member for struct nfsd_net over
to a void pointer (void __rcu *). Prepare for this by assigning
nn->nfsd_serv to an struct svc_serv pointer that is then happily
dereferenced. This eliminates what would otherwise be numerous void
pointer dereferences after the next commit.

All nfsd code what audited so that methods that hold nfsd_mutex will
continue to directly dereference nn->nfsd_serv.

Signed-off-by: Mike Snitzer <snitzer@kernel.org>
---
fs/nfsd/nfsctl.c | 21 +++++++++++++--------
fs/nfsd/nfssvc.c | 34 ++++++++++++++++++----------------
2 files changed, 31 insertions(+), 24 deletions(-)

diff --git a/fs/nfsd/nfsctl.c b/fs/nfsd/nfsctl.c
index 6fb92bb61c6d..075ada559e18 100644
--- a/fs/nfsd/nfsctl.c
+++ b/fs/nfsd/nfsctl.c
@@ -687,10 +687,11 @@ static ssize_t write_versions(struct file *file, char *buf, size_t size)
static ssize_t __write_ports_names(char *buf, struct net *net)
{
struct nfsd_net *nn = net_generic(net, nfsd_net_id);
+ struct svc_serv *serv = nn->nfsd_serv;

- if (nn->nfsd_serv == NULL)
+ if (serv == NULL)
return 0;
- return svc_xprt_names(nn->nfsd_serv, buf, SIMPLE_TRANSACTION_LIMIT);
+ return svc_xprt_names(serv, buf, SIMPLE_TRANSACTION_LIMIT);
}

/*
@@ -717,7 +718,7 @@ static ssize_t __write_ports_addfd(char *buf, struct net *net, const struct cred
serv = nn->nfsd_serv;
err = svc_addsock(serv, net, fd, buf, SIMPLE_TRANSACTION_LIMIT, cred);

- if (!serv->sv_nrthreads && list_empty(&nn->nfsd_serv->sv_permsocks))
+ if (!serv->sv_nrthreads && list_empty(&serv->sv_permsocks))
nfsd_destroy_serv(net);

return err;
@@ -765,7 +766,7 @@ static ssize_t __write_ports_addxprt(char *buf, struct net *net, const struct cr
svc_xprt_put(xprt);
}
out_err:
- if (!serv->sv_nrthreads && list_empty(&nn->nfsd_serv->sv_permsocks))
+ if (!serv->sv_nrthreads && list_empty(&serv->sv_permsocks))
nfsd_destroy_serv(net);

return err;
@@ -1674,6 +1675,7 @@ int nfsd_nl_threads_set_doit(struct sk_buff *skb, struct genl_info *info)
int *nthreads, count = 0, nrpools, i, ret = -EOPNOTSUPP, rem;
struct net *net = genl_info_net(info);
struct nfsd_net *nn = net_generic(net, nfsd_net_id);
+ struct svc_serv *serv;
const struct nlattr *attr;
const char *scope = NULL;

@@ -1708,7 +1710,8 @@ int nfsd_nl_threads_set_doit(struct sk_buff *skb, struct genl_info *info)
info->attrs[NFSD_A_SERVER_LEASETIME] ||
info->attrs[NFSD_A_SERVER_SCOPE]) {
ret = -EBUSY;
- if (nn->nfsd_serv && nn->nfsd_serv->sv_nrthreads)
+ serv = nn->nfsd_serv;
+ if (serv && serv->sv_nrthreads)
goto out_unlock;

ret = -EINVAL;
@@ -1757,6 +1760,7 @@ int nfsd_nl_threads_get_doit(struct sk_buff *skb, struct genl_info *info)
{
struct net *net = genl_info_net(info);
struct nfsd_net *nn = net_generic(net, nfsd_net_id);
+ struct svc_serv *serv;
void *hdr;
int err;

@@ -1781,11 +1785,12 @@ int nfsd_nl_threads_get_doit(struct sk_buff *skb, struct genl_info *info)
if (err)
goto err_unlock;

- if (nn->nfsd_serv) {
+ serv = nn->nfsd_serv;
+ if (serv) {
int i;

for (i = 0; i < nfsd_nrpools(net); ++i) {
- struct svc_pool *sp = &nn->nfsd_serv->sv_pools[i];
+ struct svc_pool *sp = &serv->sv_pools[i];

err = nla_put_u32(skb, NFSD_A_SERVER_THREADS,
atomic_read(&sp->sp_nrthreads));
@@ -2103,7 +2108,7 @@ int nfsd_nl_listener_set_doit(struct sk_buff *skb, struct genl_info *info)
err = ret;
}

- if (!serv->sv_nrthreads && list_empty(&nn->nfsd_serv->sv_permsocks))
+ if (!serv->sv_nrthreads && list_empty(&serv->sv_permsocks))
nfsd_destroy_serv(net);

out_unlock_mtx:
diff --git a/fs/nfsd/nfssvc.c b/fs/nfsd/nfssvc.c
index 1df9e18c510b..c16c7d630859 100644
--- a/fs/nfsd/nfssvc.c
+++ b/fs/nfsd/nfssvc.c
@@ -288,10 +288,12 @@ int nfsd_nrthreads(struct net *net)
{
int rv = 0;
struct nfsd_net *nn = net_generic(net, nfsd_net_id);
+ struct svc_serv *serv;

mutex_lock(&nfsd_mutex);
- if (nn->nfsd_serv)
- rv = nn->nfsd_serv->sv_nrthreads;
+ serv = nn->nfsd_serv;
+ if (serv)
+ rv = serv->sv_nrthreads;
mutex_unlock(&nfsd_mutex);
return rv;
}
@@ -300,16 +302,17 @@ static int nfsd_init_socks(struct net *net, const struct cred *cred)
{
int error;
struct nfsd_net *nn = net_generic(net, nfsd_net_id);
+ struct svc_serv *serv = nn->nfsd_serv;

- if (!list_empty(&nn->nfsd_serv->sv_permsocks))
+ if (!list_empty(&serv->sv_permsocks))
return 0;

- error = svc_xprt_create(nn->nfsd_serv, "udp", net, PF_INET, NFS_PORT,
+ error = svc_xprt_create(serv, "udp", net, PF_INET, NFS_PORT,
SVC_SOCK_DEFAULTS, cred);
if (error < 0)
return error;

- error = svc_xprt_create(nn->nfsd_serv, "tcp", net, PF_INET, NFS_PORT,
+ error = svc_xprt_create(serv, "tcp", net, PF_INET, NFS_PORT,
SVC_SOCK_DEFAULTS, cred);
if (error < 0)
return error;
@@ -722,11 +725,12 @@ int nfsd_create_serv(struct net *net)
int nfsd_nrpools(struct net *net)
{
struct nfsd_net *nn = net_generic(net, nfsd_net_id);
+ struct svc_serv *serv = nn->nfsd_serv;

- if (nn->nfsd_serv == NULL)
+ if (serv == NULL)
return 0;
else
- return nn->nfsd_serv->sv_nrpools;
+ return serv->sv_nrpools;
}

int nfsd_get_nrthreads(int n, int *nthreads, struct net *net)
@@ -760,14 +764,15 @@ int nfsd_set_nrthreads(int n, int *nthreads, struct net *net)
int tot = 0;
int err = 0;
struct nfsd_net *nn = net_generic(net, nfsd_net_id);
+ struct svc_serv *serv = nn->nfsd_serv;

lockdep_assert_held(&nfsd_mutex);

- if (nn->nfsd_serv == NULL || n <= 0)
+ if (serv == NULL || n <= 0)
return 0;

- if (n > nn->nfsd_serv->sv_nrpools)
- n = nn->nfsd_serv->sv_nrpools;
+ if (n > serv->sv_nrpools)
+ n = serv->sv_nrpools;

/* enforce a global maximum number of threads */
tot = 0;
@@ -790,18 +795,15 @@ int nfsd_set_nrthreads(int n, int *nthreads, struct net *net)

/* apply the new numbers */
for (i = 0; i < n; i++) {
- err = svc_set_num_threads(nn->nfsd_serv,
- &nn->nfsd_serv->sv_pools[i],
+ err = svc_set_num_threads(serv, &serv->sv_pools[i],
nthreads[i]);
if (err)
goto out;
}

/* Anything undefined in array is considered to be 0 */
- for (i = n; i < nn->nfsd_serv->sv_nrpools; ++i) {
- err = svc_set_num_threads(nn->nfsd_serv,
- &nn->nfsd_serv->sv_pools[i],
- 0);
+ for (i = n; i < serv->sv_nrpools; ++i) {
+ err = svc_set_num_threads(serv, &serv->sv_pools[i], 0);
if (err)
goto out;
}
--
2.44.0