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nfsd4: fix nfsdfs reference count loop 

We don't drop the reference on the nfsdfs filesystem with
mntput(nn->nfsd_mnt) until nfsd_exit_net(), but that won't be called
until the nfsd module's unloaded, and we can't unload the module as long
as there's a reference on nfsdfs.  So this prevents module unloading.

Fixes: 2c830dd720 ("nfsd: persist nfsd filesystem across mounts")
Reported-and-Tested-by:  Luo Xiaogang <lxgrxd@163.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
This commit is contained in:
J. Bruce Fields 2020-06-23 16:00:33 -04:00
parent 22cf8419f1
commit 681370f4b0
3 changed files with 22 additions and 11 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
fs/nfsd/nfs4state.c
View File

@ -7912,9 +7912,14 @@ nfs4_state_start_net(struct net *net)
struct nfsd_net *nn = net_generic(net, nfsd_net_id); struct nfsd_net *nn = net_generic(net, nfsd_net_id);
int ret; int ret;
ret = nfs4_state_create_net(net); ret = get_nfsdfs(net);
if (ret) if (ret)
return ret; return ret;
ret = nfs4_state_create_net(net);
if (ret) {
mntput(nn->nfsd_mnt);
return ret;
}
locks_start_grace(net, &nn->nfsd4_manager); locks_start_grace(net, &nn->nfsd4_manager);
nfsd4_client_tracking_init(net); nfsd4_client_tracking_init(net);
if (nn->track_reclaim_completes && nn->reclaim_str_hashtbl_size == 0) if (nn->track_reclaim_completes && nn->reclaim_str_hashtbl_size == 0)
@ -7984,6 +7989,7 @@ nfs4_state_shutdown_net(struct net *net)
nfsd4_client_tracking_exit(net); nfsd4_client_tracking_exit(net);
nfs4_state_destroy_net(net); nfs4_state_destroy_net(net);
mntput(nn->nfsd_mnt);
} }
void void

22
fs/nfsd/nfsctl.c
View File

@ -1424,6 +1424,18 @@ static struct file_system_type nfsd_fs_type = {
}; };
MODULE_ALIAS_FS("nfsd"); MODULE_ALIAS_FS("nfsd");
int get_nfsdfs(struct net *net)
{
struct nfsd_net *nn = net_generic(net, nfsd_net_id);
struct vfsmount *mnt;
mnt = vfs_kern_mount(&nfsd_fs_type, SB_KERNMOUNT, "nfsd", NULL);
if (IS_ERR(mnt))
return PTR_ERR(mnt);
nn->nfsd_mnt = mnt;
return 0;
}
#ifdef CONFIG_PROC_FS #ifdef CONFIG_PROC_FS
static int create_proc_exports_entry(void) static int create_proc_exports_entry(void)
{ {
@ -1451,7 +1463,6 @@ unsigned int nfsd_net_id;
static __net_init int nfsd_init_net(struct net *net) static __net_init int nfsd_init_net(struct net *net)
{ {
int retval; int retval;
struct vfsmount *mnt;
struct nfsd_net *nn = net_generic(net, nfsd_net_id); struct nfsd_net *nn = net_generic(net, nfsd_net_id);
retval = nfsd_export_init(net); retval = nfsd_export_init(net);
@ -1478,16 +1489,8 @@ static __net_init int nfsd_init_net(struct net *net)
init_waitqueue_head(&nn->ntf_wq); init_waitqueue_head(&nn->ntf_wq);
seqlock_init(&nn->boot_lock); seqlock_init(&nn->boot_lock);
mnt = vfs_kern_mount(&nfsd_fs_type, SB_KERNMOUNT, "nfsd", NULL);
if (IS_ERR(mnt)) {
retval = PTR_ERR(mnt);
goto out_mount_err;
}
nn->nfsd_mnt = mnt;
return 0; return 0;
out_mount_err:
nfsd_reply_cache_shutdown(nn);
out_drc_error: out_drc_error:
nfsd_idmap_shutdown(net); nfsd_idmap_shutdown(net);
out_idmap_error: out_idmap_error:
@ -1500,7 +1503,6 @@ static __net_exit void nfsd_exit_net(struct net *net)
{ {
struct nfsd_net *nn = net_generic(net, nfsd_net_id); struct nfsd_net *nn = net_generic(net, nfsd_net_id);
mntput(nn->nfsd_mnt);
nfsd_reply_cache_shutdown(nn); nfsd_reply_cache_shutdown(nn);
nfsd_idmap_shutdown(net); nfsd_idmap_shutdown(net);
nfsd_export_shutdown(net); nfsd_export_shutdown(net);

3
fs/nfsd/nfsd.h
View File

@ -90,6 +90,8 @@ void nfsd_destroy(struct net *net);
bool i_am_nfsd(void); bool i_am_nfsd(void);
int get_nfsdfs(struct net *);
struct nfsdfs_client { struct nfsdfs_client {
struct kref cl_ref; struct kref cl_ref;
void (*cl_release)(struct kref *kref); void (*cl_release)(struct kref *kref);
@ -100,6 +102,7 @@ struct dentry *nfsd_client_mkdir(struct nfsd_net *nn,
struct nfsdfs_client *ncl, u32 id, const struct tree_descr *); struct nfsdfs_client *ncl, u32 id, const struct tree_descr *);
void nfsd_client_rmdir(struct dentry *dentry); void nfsd_client_rmdir(struct dentry *dentry);
#if defined(CONFIG_NFSD_V2_ACL) || defined(CONFIG_NFSD_V3_ACL) #if defined(CONFIG_NFSD_V2_ACL) || defined(CONFIG_NFSD_V3_ACL)
#ifdef CONFIG_NFSD_V2_ACL #ifdef CONFIG_NFSD_V2_ACL
extern const struct svc_version nfsd_acl_version2; extern const struct svc_version nfsd_acl_version2;