NFSD: Replace /proc/fs/nfsd/supported_krb5_enctypes with a symlink

Now that I've added a file under /proc/net/rpc that is managed by
the SunRPC's Kerberos mechanism, replace NFSD's
supported_krb5_enctypes file with a symlink to the new SunRPC proc
file, which contains exactly the same content.

Remarkably, commit b0b0c0a26e84 ("nfsd: add proc file listing
kernel's gss_krb5 enctypes") added the nfsd_supported_krb5_enctypes
file in 2011, but this file has never been documented in nfsd(7).

Tested-by: Scott Mayhew <smayhew@redhat.com>
Reviewed-by: Simo Sorce <simo@redhat.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

diff --git a/fs/nfsd/nfsctl.c b/fs/nfsd/nfsctl.c
index f2a0d6ac88df5e1cc0b21c7277eb26f2acbfedd9..04474b8ccf0acb6be40e9a1686203d1da6bb59a3 100644 (file)
--- a/fs/nfsd/nfsctl.c
+++ b/fs/nfsd/nfsctl.c
@@ -14,7 +14,6 @@
 #include <linux/lockd/lockd.h>
 #include <linux/sunrpc/addr.h>
 #include <linux/sunrpc/gss_api.h>
-#include <linux/sunrpc/gss_krb5_enctypes.h>
 #include <linux/sunrpc/rpc_pipe_fs.h>
 #include <linux/module.h>
 #include <linux/fsnotify.h>
@@ -47,7 +46,6 @@ enum {
        NFSD_MaxBlkSize,
        NFSD_MaxConnections,
        NFSD_Filecache,
-       NFSD_SupportedEnctypes,
        /*
         * The below MUST come last.  Otherwise we leave a hole in nfsd_files[]
         * with !CONFIG_NFSD_V4 and simple_fill_super() goes oops
@@ -187,16 +185,6 @@ static int export_features_show(struct seq_file *m, void *v)
 
 DEFINE_SHOW_ATTRIBUTE(export_features);
 
-#if defined(CONFIG_SUNRPC_GSS) || defined(CONFIG_SUNRPC_GSS_MODULE)
-static int supported_enctypes_show(struct seq_file *m, void *v)
-{
-       seq_printf(m, KRB5_SUPPORTED_ENCTYPES);
-       return 0;
-}
-
-DEFINE_SHOW_ATTRIBUTE(supported_enctypes);
-#endif /* CONFIG_SUNRPC_GSS or CONFIG_SUNRPC_GSS_MODULE */
-
 static const struct file_operations pool_stats_operations = {
        .open           = nfsd_pool_stats_open,
        .read           = seq_read,
@@ -1150,6 +1138,9 @@ static struct inode *nfsd_get_inode(struct super_block *sb, umode_t mode)
                inode->i_op = &simple_dir_inode_operations;
                inc_nlink(inode);
                break;
+       case S_IFLNK:
+               inode->i_op = &simple_symlink_inode_operations;
+               break;
        default:
                break;
        }
@@ -1195,6 +1186,59 @@ out_err:
        goto out;
 }
 
+#if IS_ENABLED(CONFIG_SUNRPC_GSS)
+static int __nfsd_symlink(struct inode *dir, struct dentry *dentry,
+                         umode_t mode, const char *content)
+{
+       struct inode *inode;
+
+       inode = nfsd_get_inode(dir->i_sb, mode);
+       if (!inode)
+               return -ENOMEM;
+
+       inode->i_link = (char *)content;
+       inode->i_size = strlen(content);
+
+       d_add(dentry, inode);
+       inc_nlink(dir);
+       fsnotify_create(dir, dentry);
+       return 0;
+}
+
+/*
+ * @content is assumed to be a NUL-terminated string that lives
+ * longer than the symlink itself.
+ */
+static void nfsd_symlink(struct dentry *parent, const char *name,
+                        const char *content)
+{
+       struct inode *dir = parent->d_inode;
+       struct dentry *dentry;
+       int ret = -ENOMEM;
+
+       inode_lock(dir);
+       dentry = d_alloc_name(parent, name);
+       if (!dentry)
+               goto out_err;
+       ret = __nfsd_symlink(d_inode(parent), dentry, S_IFLNK | 0777, content);
+       if (ret)
+               goto out_err;
+out:
+       inode_unlock(dir);
+       return;
+out_err:
+       dput(dentry);
+       dentry = ERR_PTR(ret);
+       goto out;
+}
+#else
+static inline void nfsd_symlink(struct dentry *parent, const char *name,
+                               const char *content)
+{
+}
+
+#endif
+
 static void clear_ncl(struct inode *inode)
 {
        struct nfsdfs_client *ncl = inode->i_private;
@@ -1355,10 +1399,6 @@ static int nfsd_fill_super(struct super_block *sb, struct fs_context *fc)
                [NFSD_MaxBlkSize] = {"max_block_size", &transaction_ops, S_IWUSR|S_IRUGO},
                [NFSD_MaxConnections] = {"max_connections", &transaction_ops, S_IWUSR|S_IRUGO},
                [NFSD_Filecache] = {"filecache", &nfsd_file_cache_stats_fops, S_IRUGO},
-#if defined(CONFIG_SUNRPC_GSS) || defined(CONFIG_SUNRPC_GSS_MODULE)
-               [NFSD_SupportedEnctypes] = {"supported_krb5_enctypes",
-                                       &supported_enctypes_fops, S_IRUGO},
-#endif /* CONFIG_SUNRPC_GSS or CONFIG_SUNRPC_GSS_MODULE */
 #ifdef CONFIG_NFSD_V4
                [NFSD_Leasetime] = {"nfsv4leasetime", &transaction_ops, S_IWUSR|S_IRUSR},
                [NFSD_Gracetime] = {"nfsv4gracetime", &transaction_ops, S_IWUSR|S_IRUSR},
@@ -1371,6 +1411,8 @@ static int nfsd_fill_super(struct super_block *sb, struct fs_context *fc)
        ret = simple_fill_super(sb, 0x6e667364, nfsd_files);
        if (ret)
                return ret;
+       nfsd_symlink(sb->s_root, "supported_krb5_enctypes",
+                    "/proc/net/rpc/gss_krb5_enctypes");
        dentry = nfsd_mkdir(sb->s_root, NULL, "clients");
        if (IS_ERR(dentry))
                return PTR_ERR(dentry);