exportfs: add FILEID_INVALID to indicate invalid fid_type

This commit adds FILEID_INVALID = 0xff in fid_type to
indicate invalid fid_type

It avoids using magic number 255

Signed-off-by: Namjae Jeon <linkinjeon@gmail.com>
Signed-off-by: Vivek Trivedi <vtrivedi018@gmail.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

4 files changed, 10 insertions, 5 deletions

diff --git a/fs/exportfs/expfs.c b/fs/exportfs/expfs.c
index 29ab099e3e08..f1f1c59c2966 100644
--- a/fs/exportfs/expfs.c
+++ b/fs/exportfs/expfs.c
@@ -322,10 +322,10 @@ static int export_encode_fh(struct inode *inode, struct fid *fid,
 
         if (parent && (len < 4)) {
                 *max_len = 4;
-                return 255;
+                return FILEID_INVALID;
         } else if (len < 2) {
                 *max_len = 2;
-                return 255;
+                return FILEID_INVALID;
         }
 
         len = 2;
diff --git a/fs/fhandle.c b/fs/fhandle.c
index f775bfdd6e4a..26f12b95702a 100644
--- a/fs/fhandle.c
+++ b/fs/fhandle.c
@@ -52,7 +52,7 @@ static long do_sys_name_to_handle(struct path *path,
         handle_bytes = handle_dwords * sizeof(u32);
         handle->handle_bytes = handle_bytes;
         if ((handle->handle_bytes > f_handle.handle_bytes) ||
-            (retval == 255) || (retval == -ENOSPC)) {
+            (retval == FILEID_INVALID) || (retval == -ENOSPC)) {
                 /* As per old exportfs_encode_fh documentation
                  * we could return ENOSPC to indicate overflow
                  * But file system returned 255 always. So handle
diff --git a/fs/nfsd/nfsfh.c b/fs/nfsd/nfsfh.c
index 032af381b3aa..814afaa4458a 100644
--- a/fs/nfsd/nfsfh.c
+++ b/fs/nfsd/nfsfh.c
@@ -572,7 +572,7 @@ fh_compose(struct svc_fh *fhp, struct svc_export *exp, struct dentry *dentry,
 
                 if (inode)
                         _fh_update(fhp, exp, dentry);
-                if (fhp->fh_handle.fh_fileid_type == 255) {
+                if (fhp->fh_handle.fh_fileid_type == FILEID_INVALID) {
                         fh_put(fhp);
                         return nfserr_opnotsupp;
                 }
@@ -603,7 +603,7 @@ fh_update(struct svc_fh *fhp)
                         goto out;
 
                 _fh_update(fhp, fhp->fh_export, dentry);
-                if (fhp->fh_handle.fh_fileid_type == 255)
+                if (fhp->fh_handle.fh_fileid_type == FILEID_INVALID)
                         return nfserr_opnotsupp;
         }
 out:
diff --git a/include/linux/exportfs.h b/include/linux/exportfs.h
index 12291a7ee275..0e1452546300 100644
--- a/include/linux/exportfs.h
+++ b/include/linux/exportfs.h
@@ -83,6 +83,11 @@ enum fid_type {
          * 64 bit parent inode number.
          */
         FILEID_NILFS_WITH_PARENT = 0x62,
+
+        /*
+         * Filesystems must not use 0xff file ID.
+         */
+        FILEID_INVALID = 0xff,
 };
 
 struct fid {