v4.19.13 snapshot.
diff --git a/include/linux/fdtable.h b/include/linux/fdtable.h
new file mode 100644
index 0000000..41615f3
--- /dev/null
+++ b/include/linux/fdtable.h
@@ -0,0 +1,127 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * descriptor table internals; you almost certainly want file.h instead.
+ */
+
+#ifndef __LINUX_FDTABLE_H
+#define __LINUX_FDTABLE_H
+
+#include <linux/posix_types.h>
+#include <linux/compiler.h>
+#include <linux/spinlock.h>
+#include <linux/rcupdate.h>
+#include <linux/nospec.h>
+#include <linux/types.h>
+#include <linux/init.h>
+#include <linux/fs.h>
+
+#include <linux/atomic.h>
+
+/*
+ * The default fd array needs to be at least BITS_PER_LONG,
+ * as this is the granularity returned by copy_fdset().
+ */
+#define NR_OPEN_DEFAULT BITS_PER_LONG
+
+struct fdtable {
+ unsigned int max_fds;
+ struct file __rcu **fd; /* current fd array */
+ unsigned long *close_on_exec;
+ unsigned long *open_fds;
+ unsigned long *full_fds_bits;
+ struct rcu_head rcu;
+};
+
+static inline bool close_on_exec(unsigned int fd, const struct fdtable *fdt)
+{
+ return test_bit(fd, fdt->close_on_exec);
+}
+
+static inline bool fd_is_open(unsigned int fd, const struct fdtable *fdt)
+{
+ return test_bit(fd, fdt->open_fds);
+}
+
+/*
+ * Open file table structure
+ */
+struct files_struct {
+ /*
+ * read mostly part
+ */
+ atomic_t count;
+ bool resize_in_progress;
+ wait_queue_head_t resize_wait;
+
+ struct fdtable __rcu *fdt;
+ struct fdtable fdtab;
+ /*
+ * written part on a separate cache line in SMP
+ */
+ spinlock_t file_lock ____cacheline_aligned_in_smp;
+ unsigned int next_fd;
+ unsigned long close_on_exec_init[1];
+ unsigned long open_fds_init[1];
+ unsigned long full_fds_bits_init[1];
+ struct file __rcu * fd_array[NR_OPEN_DEFAULT];
+};
+
+struct file_operations;
+struct vfsmount;
+struct dentry;
+
+#define rcu_dereference_check_fdtable(files, fdtfd) \
+ rcu_dereference_check((fdtfd), lockdep_is_held(&(files)->file_lock))
+
+#define files_fdtable(files) \
+ rcu_dereference_check_fdtable((files), (files)->fdt)
+
+/*
+ * The caller must ensure that fd table isn't shared or hold rcu or file lock
+ */
+static inline struct file *__fcheck_files(struct files_struct *files, unsigned int fd)
+{
+ struct fdtable *fdt = rcu_dereference_raw(files->fdt);
+
+ if (fd < fdt->max_fds) {
+ fd = array_index_nospec(fd, fdt->max_fds);
+ return rcu_dereference_raw(fdt->fd[fd]);
+ }
+ return NULL;
+}
+
+static inline struct file *fcheck_files(struct files_struct *files, unsigned int fd)
+{
+ RCU_LOCKDEP_WARN(!rcu_read_lock_held() &&
+ !lockdep_is_held(&files->file_lock),
+ "suspicious rcu_dereference_check() usage");
+ return __fcheck_files(files, fd);
+}
+
+/*
+ * Check whether the specified fd has an open file.
+ */
+#define fcheck(fd) fcheck_files(current->files, fd)
+
+struct task_struct;
+
+struct files_struct *get_files_struct(struct task_struct *);
+void put_files_struct(struct files_struct *fs);
+void reset_files_struct(struct files_struct *);
+int unshare_files(struct files_struct **);
+struct files_struct *dup_fd(struct files_struct *, int *) __latent_entropy;
+void do_close_on_exec(struct files_struct *);
+int iterate_fd(struct files_struct *, unsigned,
+ int (*)(const void *, struct file *, unsigned),
+ const void *);
+
+extern int __alloc_fd(struct files_struct *files,
+ unsigned start, unsigned end, unsigned flags);
+extern void __fd_install(struct files_struct *files,
+ unsigned int fd, struct file *file);
+extern int __close_fd(struct files_struct *files,
+ unsigned int fd);
+
+extern struct kmem_cache *files_cachep;
+
+#endif /* __LINUX_FDTABLE_H */