nfsd: new interface to advertise export features

Soon we will add the new V4ROOT flag, and allow the INSECURE flag to
vary by pseudoflavor.  It would be useful for nfs-utils (for example,
for improved exportfs error reporting) to be able to know when this
happens.  Use this new interface for that purpose.

Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>

2 files changed, 23 insertions, 1 deletions

diff --git a/fs/nfsd/nfsctl.c b/fs/nfsd/nfsctl.c
index 0415680d3f58..e7051ac4dc73 100644
--- a/fs/nfsd/nfsctl.c
+++ b/fs/nfsd/nfsctl.c
@@ -31,6 +31,7 @@ enum {
         NFSD_Getfd,
         NFSD_Getfs,
         NFSD_List,
+        NFSD_Export_features,
         NFSD_Fh,
         NFSD_FO_UnlockIP,
         NFSD_FO_UnlockFS,
@@ -149,6 +150,24 @@ static const struct file_operations exports_operations = {
         .owner          = THIS_MODULE,
 };
 
+static int export_features_show(struct seq_file *m, void *v)
+{
+        seq_printf(m, "0x%x 0x%x\n", NFSEXP_ALLFLAGS, NFSEXP_SECINFO_FLAGS);
+        return 0;
+}
+
+static int export_features_open(struct inode *inode, struct file *file)
+{
+        return single_open(file, export_features_show, NULL);
+}
+
+static struct file_operations export_features_operations = {
+        .open           = export_features_open,
+        .read           = seq_read,
+        .llseek         = seq_lseek,
+        .release        = single_release,
+};
+
 extern int nfsd_pool_stats_open(struct inode *inode, struct file *file);
 extern int nfsd_pool_stats_release(struct inode *inode, struct file *file);
 
@@ -1306,6 +1325,8 @@ static int nfsd_fill_super(struct super_block * sb, void * data, int silent)
                 [NFSD_Getfd] = {".getfd", &transaction_ops, S_IWUSR|S_IRUSR},
                 [NFSD_Getfs] = {".getfs", &transaction_ops, S_IWUSR|S_IRUSR},
                 [NFSD_List] = {"exports", &exports_operations, S_IRUGO},
+                [NFSD_Export_features] = {"export_features",
+                                        &export_features_operations, S_IRUGO},
                 [NFSD_FO_UnlockIP] = {"unlock_ip",
                                         &transaction_ops, S_IWUSR|S_IRUSR},
                 [NFSD_FO_UnlockFS] = {"unlock_filesystem",
diff --git a/include/linux/nfsd/export.h b/include/linux/nfsd/export.h
index ef3d416fcf67..4f1df1d7312c 100644
--- a/include/linux/nfsd/export.h
+++ b/include/linux/nfsd/export.h
@@ -39,7 +39,8 @@
 #define NFSEXP_FSID             0x2000
 #define NFSEXP_CROSSMOUNT       0x4000
 #define NFSEXP_NOACL            0x8000  /* reserved for possible ACL related use */
-#define NFSEXP_ALLFLAGS         0xFE3F
+/* All flags that we claim to support.  (Note we don't support NOACL.) */
+#define NFSEXP_ALLFLAGS         0x7E3F
 
 /* The flags that may vary depending on security flavor: */
 #define NFSEXP_SECINFO_FLAGS    (NFSEXP_READONLY | NFSEXP_ROOTSQUASH \