nfs: disintegrate UAPI for nfs

This is to complete part of the Userspace API (UAPI) disintegration for which
the preparatory patches were pulled recently.  After these patches, userspace
headers will be segregated into:

        include/uapi/linux/.../foo.h

for the userspace interface stuff, and:

        include/linux/.../foo.h

for the strictly kernel internal stuff.

Signed-off-by: J. Bruce Fields <bfields@redhat.com>

1 files changed, 549 insertions, 24 deletions

diff --git a/fs/file.c b/fs/file.c
index ba3f6053025c..0f1bda4bebfa 100644
--- a/fs/file.c
+++ b/fs/file.c
@@ -6,6 +6,7 @@
  *  Manage the dynamic fd arrays in the process files_struct.
  */
 
+#include <linux/syscalls.h>
 #include <linux/export.h>
 #include <linux/fs.h>
 #include <linux/mm.h>
@@ -84,22 +85,14 @@ static void free_fdtable_work(struct work_struct *work)
 	}
 }
 
-void free_fdtable_rcu(struct rcu_head *rcu)
+static void free_fdtable_rcu(struct rcu_head *rcu)
 {
 	struct fdtable *fdt = container_of(rcu, struct fdtable, rcu);
 	struct fdtable_defer *fddef;
 
 	BUG_ON(!fdt);
+	BUG_ON(fdt->max_fds <= NR_OPEN_DEFAULT);
 
-	if (fdt->max_fds <= NR_OPEN_DEFAULT) {
-		/*
-		 * This fdtable is embedded in the files structure and that
-		 * structure itself is getting destroyed.
-		 */
-		kmem_cache_free(files_cachep,
-				container_of(fdt, struct files_struct, fdtab));
-		return;
-	}
 	if (!is_vmalloc_addr(fdt->fd) && !is_vmalloc_addr(fdt->open_fds)) {
 		kfree(fdt->fd);
 		kfree(fdt->open_fds);
@@ -229,7 +222,7 @@ static int expand_fdtable(struct files_struct *files, int nr)
 		copy_fdtable(new_fdt, cur_fdt);
 		rcu_assign_pointer(files->fdt, new_fdt);
 		if (cur_fdt->max_fds > NR_OPEN_DEFAULT)
-			free_fdtable(cur_fdt);
+			call_rcu(&cur_fdt->rcu, free_fdtable_rcu);
 	} else {
 		/* Somebody else expanded, so undo our attempt */
 		__free_fdtable(new_fdt);
@@ -245,19 +238,12 @@ static int expand_fdtable(struct files_struct *files, int nr)
  * expanded and execution may have blocked.
  * The files->file_lock should be held on entry, and will be held on exit.
  */
-int expand_files(struct files_struct *files, int nr)
+static int expand_files(struct files_struct *files, int nr)
 {
 	struct fdtable *fdt;
 
 	fdt = files_fdtable(files);
 
-	/*
-	 * N.B. For clone tasks sharing a files structure, this test
-	 * will limit the total number of files that can be opened.
-	 */
-	if (nr >= rlimit(RLIMIT_NOFILE))
-		return -EMFILE;
-
 	/* Do we need to expand? */
 	if (nr < fdt->max_fds)
 		return 0;
@@ -270,6 +256,26 @@ int expand_files(struct files_struct *files, int nr)
 	return expand_fdtable(files, nr);
 }
 
+static inline void __set_close_on_exec(int fd, struct fdtable *fdt)
+{
+	__set_bit(fd, fdt->close_on_exec);
+}
+
+static inline void __clear_close_on_exec(int fd, struct fdtable *fdt)
+{
+	__clear_bit(fd, fdt->close_on_exec);
+}
+
+static inline void __set_open_fd(int fd, struct fdtable *fdt)
+{
+	__set_bit(fd, fdt->open_fds);
+}
+
+static inline void __clear_open_fd(int fd, struct fdtable *fdt)
+{
+	__clear_bit(fd, fdt->open_fds);
+}
+
 static int count_open_files(struct fdtable *fdt)
 {
 	int size = fdt->max_fds;
@@ -395,6 +401,95 @@ out:
 	return NULL;
 }
 
+static void close_files(struct files_struct * files)
+{
+	int i, j;
+	struct fdtable *fdt;
+
+	j = 0;
+
+	/*
+	 * It is safe to dereference the fd table without RCU or
+	 * ->file_lock because this is the last reference to the
+	 * files structure.  But use RCU to shut RCU-lockdep up.
+	 */
+	rcu_read_lock();
+	fdt = files_fdtable(files);
+	rcu_read_unlock();
+	for (;;) {
+		unsigned long set;
+		i = j * BITS_PER_LONG;
+		if (i >= fdt->max_fds)
+			break;
+		set = fdt->open_fds[j++];
+		while (set) {
+			if (set & 1) {
+				struct file * file = xchg(&fdt->fd[i], NULL);
+				if (file) {
+					filp_close(file, files);
+					cond_resched();
+				}
+			}
+			i++;
+			set >>= 1;
+		}
+	}
+}
+
+struct files_struct *get_files_struct(struct task_struct *task)
+{
+	struct files_struct *files;
+
+	task_lock(task);
+	files = task->files;
+	if (files)
+		atomic_inc(&files->count);
+	task_unlock(task);
+
+	return files;
+}
+
+void put_files_struct(struct files_struct *files)
+{
+	struct fdtable *fdt;
+
+	if (atomic_dec_and_test(&files->count)) {
+		close_files(files);
+		/* not really needed, since nobody can see us */
+		rcu_read_lock();
+		fdt = files_fdtable(files);
+		rcu_read_unlock();
+		/* free the arrays if they are not embedded */
+		if (fdt != &files->fdtab)
+			__free_fdtable(fdt);
+		kmem_cache_free(files_cachep, files);
+	}
+}
+
+void reset_files_struct(struct files_struct *files)
+{
+	struct task_struct *tsk = current;
+	struct files_struct *old;
+
+	old = tsk->files;
+	task_lock(tsk);
+	tsk->files = files;
+	task_unlock(tsk);
+	put_files_struct(old);
+}
+
+void exit_files(struct task_struct *tsk)
+{
+	struct files_struct * files = tsk->files;
+
+	if (files) {
+		task_lock(tsk);
+		tsk->files = NULL;
+		task_unlock(tsk);
+		put_files_struct(files);
+	}
+}
+
 static void __devinit fdtable_defer_list_init(int cpu)
 {
 	struct fdtable_defer *fddef = &per_cpu(fdtable_defer_list, cpu);
@@ -424,12 +519,18 @@ struct files_struct init_files = {
 	.file_lock	= __SPIN_LOCK_UNLOCKED(init_task.file_lock),
 };
 
+void daemonize_descriptors(void)
+{
+	atomic_inc(&init_files.count);
+	reset_files_struct(&init_files);
+}
+
 /*
  * allocate a file descriptor, mark it busy.
  */
-int alloc_fd(unsigned start, unsigned flags)
+int __alloc_fd(struct files_struct *files,
+	       unsigned start, unsigned end, unsigned flags)
 {
-	struct files_struct *files = current->files;
 	unsigned int fd;
 	int error;
 	struct fdtable *fdt;
@@ -444,6 +545,14 @@ repeat:
 	if (fd < fdt->max_fds)
 		fd = find_next_zero_bit(fdt->open_fds, fdt->max_fds, fd);
 
+	/*
+	 * N.B. For clone tasks sharing a files structure, this test
+	 * will limit the total number of files that can be opened.
+	 */
+	error = -EMFILE;
+	if (fd >= end)
+		goto out;
+
 	error = expand_files(files, fd);
 	if (error < 0)
 		goto out;
@@ -477,8 +586,424 @@ out:
 	return error;
 }
 
-int get_unused_fd(void)
+static int alloc_fd(unsigned start, unsigned flags)
+{
+	return __alloc_fd(current->files, start, rlimit(RLIMIT_NOFILE), flags);
+}
+
+int get_unused_fd_flags(unsigned flags)
+{
+	return __alloc_fd(current->files, 0, rlimit(RLIMIT_NOFILE), flags);
+}
+EXPORT_SYMBOL(get_unused_fd_flags);
+
+static void __put_unused_fd(struct files_struct *files, unsigned int fd)
+{
+	struct fdtable *fdt = files_fdtable(files);
+	__clear_open_fd(fd, fdt);
+	if (fd < files->next_fd)
+		files->next_fd = fd;
+}
+
+void put_unused_fd(unsigned int fd)
+{
+	struct files_struct *files = current->files;
+	spin_lock(&files->file_lock);
+	__put_unused_fd(files, fd);
+	spin_unlock(&files->file_lock);
+}
+
+EXPORT_SYMBOL(put_unused_fd);
+
+/*
+ * Install a file pointer in the fd array.
+ *
+ * The VFS is full of places where we drop the files lock between
+ * setting the open_fds bitmap and installing the file in the file
+ * array.  At any such point, we are vulnerable to a dup2() race
+ * installing a file in the array before us.  We need to detect this and
+ * fput() the struct file we are about to overwrite in this case.
+ *
+ * It should never happen - if we allow dup2() do it, _really_ bad things
+ * will follow.
+ *
+ * NOTE: __fd_install() variant is really, really low-level; don't
+ * use it unless you are forced to by truly lousy API shoved down
+ * your throat.  'files' *MUST* be either current->files or obtained
+ * by get_files_struct(current) done by whoever had given it to you,
+ * or really bad things will happen.  Normally you want to use
+ * fd_install() instead.
+ */
+
+void __fd_install(struct files_struct *files, unsigned int fd,
+		struct file *file)
+{
+	struct fdtable *fdt;
+	spin_lock(&files->file_lock);
+	fdt = files_fdtable(files);
+	BUG_ON(fdt->fd[fd] != NULL);
+	rcu_assign_pointer(fdt->fd[fd], file);
+	spin_unlock(&files->file_lock);
+}
+
+void fd_install(unsigned int fd, struct file *file)
 {
-	return alloc_fd(0, 0);
+	__fd_install(current->files, fd, file);
+}
+
+EXPORT_SYMBOL(fd_install);
+
+/*
+ * The same warnings as for __alloc_fd()/__fd_install() apply here...
+ */
+int __close_fd(struct files_struct *files, unsigned fd)
+{
+	struct file *file;
+	struct fdtable *fdt;
+
+	spin_lock(&files->file_lock);
+	fdt = files_fdtable(files);
+	if (fd >= fdt->max_fds)
+		goto out_unlock;
+	file = fdt->fd[fd];
+	if (!file)
+		goto out_unlock;
+	rcu_assign_pointer(fdt->fd[fd], NULL);
+	__clear_close_on_exec(fd, fdt);
+	__put_unused_fd(files, fd);
+	spin_unlock(&files->file_lock);
+	return filp_close(file, files);
+
+out_unlock:
+	spin_unlock(&files->file_lock);
+	return -EBADF;
+}
+
+void do_close_on_exec(struct files_struct *files)
+{
+	unsigned i;
+	struct fdtable *fdt;
+
+	/* exec unshares first */
+	BUG_ON(atomic_read(&files->count) != 1);
+	spin_lock(&files->file_lock);
+	for (i = 0; ; i++) {
+		unsigned long set;
+		unsigned fd = i * BITS_PER_LONG;
+		fdt = files_fdtable(files);
+		if (fd >= fdt->max_fds)
+			break;
+		set = fdt->close_on_exec[i];
+		if (!set)
+			continue;
+		fdt->close_on_exec[i] = 0;
+		for ( ; set ; fd++, set >>= 1) {
+			struct file *file;
+			if (!(set & 1))
+				continue;
+			file = fdt->fd[fd];
+			if (!file)
+				continue;
+			rcu_assign_pointer(fdt->fd[fd], NULL);
+			__put_unused_fd(files, fd);
+			spin_unlock(&files->file_lock);
+			filp_close(file, files);
+			cond_resched();
+			spin_lock(&files->file_lock);
+		}
+
+	}
+	spin_unlock(&files->file_lock);
+}
+
+struct file *fget(unsigned int fd)
+{
+	struct file *file;
+	struct files_struct *files = current->files;
+
+	rcu_read_lock();
+	file = fcheck_files(files, fd);
+	if (file) {
+		/* File object ref couldn't be taken */
+		if (file->f_mode & FMODE_PATH ||
+		    !atomic_long_inc_not_zero(&file->f_count))
+			file = NULL;
+	}
+	rcu_read_unlock();
+
+	return file;
+}
+
+EXPORT_SYMBOL(fget);
+
+struct file *fget_raw(unsigned int fd)
+{
+	struct file *file;
+	struct files_struct *files = current->files;
+
+	rcu_read_lock();
+	file = fcheck_files(files, fd);
+	if (file) {
+		/* File object ref couldn't be taken */
+		if (!atomic_long_inc_not_zero(&file->f_count))
+			file = NULL;
+	}
+	rcu_read_unlock();
+
+	return file;
+}
+
+EXPORT_SYMBOL(fget_raw);
+
+/*
+ * Lightweight file lookup - no refcnt increment if fd table isn't shared.
+ *
+ * You can use this instead of fget if you satisfy all of the following
+ * conditions:
+ * 1) You must call fput_light before exiting the syscall and returning control
+ *    to userspace (i.e. you cannot remember the returned struct file * after
+ *    returning to userspace).
+ * 2) You must not call filp_close on the returned struct file * in between
+ *    calls to fget_light and fput_light.
+ * 3) You must not clone the current task in between the calls to fget_light
+ *    and fput_light.
+ *
+ * The fput_needed flag returned by fget_light should be passed to the
+ * corresponding fput_light.
+ */
+struct file *fget_light(unsigned int fd, int *fput_needed)
+{
+	struct file *file;
+	struct files_struct *files = current->files;
+
+	*fput_needed = 0;
+	if (atomic_read(&files->count) == 1) {
+		file = fcheck_files(files, fd);
+		if (file && (file->f_mode & FMODE_PATH))
+			file = NULL;
+	} else {
+		rcu_read_lock();
+		file = fcheck_files(files, fd);
+		if (file) {
+			if (!(file->f_mode & FMODE_PATH) &&
+			    atomic_long_inc_not_zero(&file->f_count))
+				*fput_needed = 1;
+			else
+				/* Didn't get the reference, someone's freed */
+				file = NULL;
+		}
+		rcu_read_unlock();
+	}
+
+	return file;
+}
+EXPORT_SYMBOL(fget_light);
+
+struct file *fget_raw_light(unsigned int fd, int *fput_needed)
+{
+	struct file *file;
+	struct files_struct *files = current->files;
+
+	*fput_needed = 0;
+	if (atomic_read(&files->count) == 1) {
+		file = fcheck_files(files, fd);
+	} else {
+		rcu_read_lock();
+		file = fcheck_files(files, fd);
+		if (file) {
+			if (atomic_long_inc_not_zero(&file->f_count))
+				*fput_needed = 1;
+			else
+				/* Didn't get the reference, someone's freed */
+				file = NULL;
+		}
+		rcu_read_unlock();
+	}
+
+	return file;
+}
+
+void set_close_on_exec(unsigned int fd, int flag)
+{
+	struct files_struct *files = current->files;
+	struct fdtable *fdt;
+	spin_lock(&files->file_lock);
+	fdt = files_fdtable(files);
+	if (flag)
+		__set_close_on_exec(fd, fdt);
+	else
+		__clear_close_on_exec(fd, fdt);
+	spin_unlock(&files->file_lock);
+}
+
+bool get_close_on_exec(unsigned int fd)
+{
+	struct files_struct *files = current->files;
+	struct fdtable *fdt;
+	bool res;
+	rcu_read_lock();
+	fdt = files_fdtable(files);
+	res = close_on_exec(fd, fdt);
+	rcu_read_unlock();
+	return res;
+}
+
+static int do_dup2(struct files_struct *files,
+	struct file *file, unsigned fd, unsigned flags)
+{
+	struct file *tofree;
+	struct fdtable *fdt;
+
+	/*
+	 * We need to detect attempts to do dup2() over allocated but still
+	 * not finished descriptor.  NB: OpenBSD avoids that at the price of
+	 * extra work in their equivalent of fget() - they insert struct
+	 * file immediately after grabbing descriptor, mark it larval if
+	 * more work (e.g. actual opening) is needed and make sure that
+	 * fget() treats larval files as absent.  Potentially interesting,
+	 * but while extra work in fget() is trivial, locking implications
+	 * and amount of surgery on open()-related paths in VFS are not.
+	 * FreeBSD fails with -EBADF in the same situation, NetBSD "solution"
+	 * deadlocks in rather amusing ways, AFAICS.  All of that is out of
+	 * scope of POSIX or SUS, since neither considers shared descriptor
+	 * tables and this condition does not arise without those.
+	 */
+	fdt = files_fdtable(files);
+	tofree = fdt->fd[fd];
+	if (!tofree && fd_is_open(fd, fdt))
+		goto Ebusy;
+	get_file(file);
+	rcu_assign_pointer(fdt->fd[fd], file);
+	__set_open_fd(fd, fdt);
+	if (flags & O_CLOEXEC)
+		__set_close_on_exec(fd, fdt);
+	else
+		__clear_close_on_exec(fd, fdt);
+	spin_unlock(&files->file_lock);
+
+	if (tofree)
+		filp_close(tofree, files);
+
+	return fd;
+
+Ebusy:
+	spin_unlock(&files->file_lock);
+	return -EBUSY;
+}
+
+int replace_fd(unsigned fd, struct file *file, unsigned flags)
+{
+	int err;
+	struct files_struct *files = current->files;
+
+	if (!file)
+		return __close_fd(files, fd);
+
+	if (fd >= rlimit(RLIMIT_NOFILE))
+		return -EMFILE;
+
+	spin_lock(&files->file_lock);
+	err = expand_files(files, fd);
+	if (unlikely(err < 0))
+		goto out_unlock;
+	return do_dup2(files, file, fd, flags);
+
+out_unlock:
+	spin_unlock(&files->file_lock);
+	return err;
+}
+
+SYSCALL_DEFINE3(dup3, unsigned int, oldfd, unsigned int, newfd, int, flags)
+{
+	int err = -EBADF;
+	struct file *file;
+	struct files_struct *files = current->files;
+
+	if ((flags & ~O_CLOEXEC) != 0)
+		return -EINVAL;
+
+	if (newfd >= rlimit(RLIMIT_NOFILE))
+		return -EMFILE;
+
+	spin_lock(&files->file_lock);
+	err = expand_files(files, newfd);
+	file = fcheck(oldfd);
+	if (unlikely(!file))
+		goto Ebadf;
+	if (unlikely(err < 0)) {
+		if (err == -EMFILE)
+			goto Ebadf;
+		goto out_unlock;
+	}
+	return do_dup2(files, file, newfd, flags);
+
+Ebadf:
+	err = -EBADF;
+out_unlock:
+	spin_unlock(&files->file_lock);
+	return err;
+}
+
+SYSCALL_DEFINE2(dup2, unsigned int, oldfd, unsigned int, newfd)
+{
+	if (unlikely(newfd == oldfd)) { /* corner case */
+		struct files_struct *files = current->files;
+		int retval = oldfd;
+
+		rcu_read_lock();
+		if (!fcheck_files(files, oldfd))
+			retval = -EBADF;
+		rcu_read_unlock();
+		return retval;
+	}
+	return sys_dup3(oldfd, newfd, 0);
+}
+
+SYSCALL_DEFINE1(dup, unsigned int, fildes)
+{
+	int ret = -EBADF;
+	struct file *file = fget_raw(fildes);
+
+	if (file) {
+		ret = get_unused_fd();
+		if (ret >= 0)
+			fd_install(ret, file);
+		else
+			fput(file);
+	}
+	return ret;
+}
+
+int f_dupfd(unsigned int from, struct file *file, unsigned flags)
+{
+	int err;
+	if (from >= rlimit(RLIMIT_NOFILE))
+		return -EINVAL;
+	err = alloc_fd(from, flags);
+	if (err >= 0) {
+		get_file(file);
+		fd_install(err, file);
+	}
+	return err;
+}
+
+int iterate_fd(struct files_struct *files, unsigned n,
+		int (*f)(const void *, struct file *, unsigned),
+		const void *p)
+{
+	struct fdtable *fdt;
+	struct file *file;
+	int res = 0;
+	if (!files)
+		return 0;
+	spin_lock(&files->file_lock);
+	fdt = files_fdtable(files);
+	while (!res && n < fdt->max_fds) {
+		file = rcu_dereference_check_fdtable(files, fdt->fd[n++]);
+		if (file)
+			res = f(p, file, n);
+	}
+	spin_unlock(&files->file_lock);
+	return res;
 }
-EXPORT_SYMBOL(get_unused_fd);
+EXPORT_SYMBOL(iterate_fd);