exportfs: fix 32-bit nfsd handling of 64-bit inode numbers

Symptoms were spurious -ENOENTs on stat of an NFS filesystem from a
32-bit NFS server exporting a very large XFS filesystem, when the
server's cache is cold (so the inodes in question are not in cache).

Reviewed-by: Christoph Hellwig <hch@lst.de>
Reported-by: Trevor Cordes <trevor@tecnopolis.ca>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 16 insertions, 2 deletions

diff --git a/fs/exportfs/expfs.c b/fs/exportfs/expfs.c
index a235f0016889..c43fe9b39ff2 100644
--- a/fs/exportfs/expfs.c
+++ b/fs/exportfs/expfs.c
@@ -215,7 +215,7 @@ struct getdents_callback {
         struct dir_context ctx;
         char *name;             /* name that was found. It already points to a
                                    buffer NAME_MAX+1 is size */
-        unsigned long ino;      /* the inum we are looking for */
+        u64 ino;                /* the inum we are looking for */
         int found;              /* inode matched? */
         int sequence;           /* sequence counter */
 };
@@ -255,10 +255,14 @@ static int get_name(const struct path *path, char *name, struct dentry *child)
         struct inode *dir = path->dentry->d_inode;
         int error;
         struct file *file;
+        struct kstat stat;
+        struct path child_path = {
+                .mnt = path->mnt,
+                .dentry = child,
+        };
         struct getdents_callback buffer = {
                 .ctx.actor = filldir_one,
                 .name = name,
-                .ino = child->d_inode->i_ino
         };
 
         error = -ENOTDIR;
@@ -268,6 +272,16 @@ static int get_name(const struct path *path, char *name, struct dentry *child)
         if (!dir->i_fop)
                 goto out;
         /*
+         * inode->i_ino is unsigned long, kstat->ino is u64, so the
+         * former would be insufficient on 32-bit hosts when the
+         * filesystem supports 64-bit inode numbers.  So we need to
+         * actually call ->getattr, not just read i_ino:
+         */
+        error = vfs_getattr_nosec(&child_path, &stat);
+        if (error)
+                return error;
+        buffer.ino = stat.ino;
+        /*
          * Open the directory ...
          */
         file = dentry_open(path, O_RDONLY, cred);