+/*
+ * We do this buffering because we must not call back into the file
+ * system's ->lookup() method from the filldir callback. That may well
+ * deadlock a number of file systems.
+ *
+ * This is based heavily on the implementation of same in XFS.
+ */
+struct buffered_dirent {
+ u64 ino;
+ loff_t offset;
+ int namlen;
+ unsigned int d_type;
+ char name[];
+};
+
+struct readdir_data {
+ char *dirent;
+ size_t used;
+ int full;
+};
+
+static int nfsd_buffered_filldir(void *__buf, const char *name, int namlen,
+ loff_t offset, u64 ino, unsigned int d_type)
+{
+ struct readdir_data *buf = __buf;
+ struct buffered_dirent *de = (void *)(buf->dirent + buf->used);
+ unsigned int reclen;
+
+ reclen = ALIGN(sizeof(struct buffered_dirent) + namlen, sizeof(u64));
+ if (buf->used + reclen > PAGE_SIZE) {
+ buf->full = 1;
+ return -EINVAL;
+ }
+
+ de->namlen = namlen;
+ de->offset = offset;
+ de->ino = ino;
+ de->d_type = d_type;
+ memcpy(de->name, name, namlen);
+ buf->used += reclen;
+
+ return 0;
+}
+
+static int nfsd_buffered_readdir(struct file *file, filldir_t func,
+ struct readdir_cd *cdp, loff_t *offsetp)
+{
+ struct readdir_data buf;
+ struct buffered_dirent *de;
+ int host_err;
+ int size;
+ loff_t offset;
+
+ buf.dirent = (void *)__get_free_page(GFP_KERNEL);
+ if (!buf.dirent)
+ return -ENOMEM;
+
+ offset = *offsetp;
+ cdp->err = nfserr_eof; /* will be cleared on successful read */
+
+ while (1) {
+ unsigned int reclen;
+
+ buf.used = 0;
+ buf.full = 0;
+
+ host_err = vfs_readdir(file, nfsd_buffered_filldir, &buf);
+ if (buf.full)
+ host_err = 0;
+
+ if (host_err < 0)
+ break;
+
+ size = buf.used;
+
+ if (!size)
+ break;
+
+ de = (struct buffered_dirent *)buf.dirent;
+ while (size > 0) {
+ offset = de->offset;
+
+ if (func(cdp, de->name, de->namlen, de->offset,
+ de->ino, de->d_type))
+ goto done;
+
+ if (cdp->err != nfs_ok)
+ goto done;
+
+ reclen = ALIGN(sizeof(*de) + de->namlen,
+ sizeof(u64));
+ size -= reclen;
+ de = (struct buffered_dirent *)((char *)de + reclen);
+ }
+ offset = vfs_llseek(file, 0, SEEK_CUR);
+ cdp->err = nfserr_eof;
+ if (!buf.full)
+ break;
+ }
+
+ done:
+ free_page((unsigned long)(buf.dirent));
+
+ if (host_err)
+ return nfserrno(host_err);
+
+ *offsetp = offset;
+ return cdp->err;
+}
+