Commit 8fd3395e authored by Al Viro's avatar Al Viro
Browse files

get rid of ...lookup...fdget_rcu() family 



Once upon a time, predecessors of those used to do file lookup
without bumping a refcount, provided that caller held rcu_read_lock()
across the lookup and whatever it wanted to read from the struct
file found.  When struct file allocation switched to SLAB_TYPESAFE_BY_RCU,
that stopped being feasible and these primitives started to bump the
file refcount for lookup result, requiring the caller to call fput()
afterwards.

But that turned them pointless - e.g.
	rcu_read_lock();
	file = lookup_fdget_rcu(fd);
	rcu_read_unlock();
is equivalent to
	file = fget_raw(fd);
and all callers of lookup_fdget_rcu() are of that form.  Similarly,
task_lookup_fdget_rcu() calls can be replaced with calling fget_task().
task_lookup_next_fdget_rcu() doesn't have direct counterparts, but
its callers would be happier if we replaced it with an analogue that
deals with RCU internally.

Reviewed-by: default avatarChristian Brauner <brauner@kernel.org>
Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent 8cf0b939

arch/powerpc/platforms/cell/spufs/coredump.c

+1 −3
Original line number Diff line number Diff line
@@ -73,9 +73,7 @@ static struct spu_context *coredump_next_context(int *fd) 
		return NULL;

	*fd = n - 1;



	rcu_read_lock();

	file = lookup_fdget_rcu(*fd);

	rcu_read_unlock();

	file = fget_raw(*fd);

	if (file) {

		ctx = SPUFS_I(file_inode(file))->i_ctx;

		get_spu_context(ctx);

fs/file.c

+4 −24
Original line number Diff line number Diff line
@@ -1037,29 +1037,7 @@ struct file *fget_task(struct task_struct *task, unsigned int fd) 
	return file;

}



struct file *lookup_fdget_rcu(unsigned int fd)

{

	return __fget_files_rcu(current->files, fd, 0);



}

EXPORT_SYMBOL_GPL(lookup_fdget_rcu);



struct file *task_lookup_fdget_rcu(struct task_struct *task, unsigned int fd)

{

	/* Must be called with rcu_read_lock held */

	struct files_struct *files;

	struct file *file = NULL;



	task_lock(task);

	files = task->files;

	if (files)

		file = __fget_files_rcu(files, fd, 0);

	task_unlock(task);



	return file;

}



struct file *task_lookup_next_fdget_rcu(struct task_struct *task, unsigned int *ret_fd)

struct file *fget_task_next(struct task_struct *task, unsigned int *ret_fd)

{

	/* Must be called with rcu_read_lock held */

	struct files_struct *files;
@@ -1069,17 +1047,19 @@ struct file *task_lookup_next_fdget_rcu(struct task_struct *task, unsigned int * 
	task_lock(task);

	files = task->files;

	if (files) {

		rcu_read_lock();

		for (; fd < files_fdtable(files)->max_fds; fd++) {

			file = __fget_files_rcu(files, fd, 0);

			if (file)

				break;

		}

		rcu_read_unlock();

	}

	task_unlock(task);

	*ret_fd = fd;

	return file;

}

EXPORT_SYMBOL(task_lookup_next_fdget_rcu);

EXPORT_SYMBOL(fget_task_next);



/*

 * Lightweight file lookup - no refcnt increment if fd table isn't shared.

fs/gfs2/glock.c

+2 −10
Original line number Diff line number Diff line
@@ -34,7 +34,6 @@ 
#include <linux/lockref.h>

#include <linux/rhashtable.h>

#include <linux/pid_namespace.h>

#include <linux/fdtable.h>

#include <linux/file.h>



#include "gfs2.h"
@@ -2768,25 +2767,18 @@ static struct file *gfs2_glockfd_next_file(struct gfs2_glockfd_iter *i) 
		i->file = NULL;

	}



	rcu_read_lock();

	for(;; i->fd++) {

		struct inode *inode;



		i->file = task_lookup_next_fdget_rcu(i->task, &i->fd);

		i->file = fget_task_next(i->task, &i->fd);

		if (!i->file) {

			i->fd = 0;

			break;

		}



		inode = file_inode(i->file);

		if (inode->i_sb == i->sb)

		if (file_inode(i->file)->i_sb == i->sb)

			break;



		rcu_read_unlock();

		fput(i->file);

		rcu_read_lock();

	}

	rcu_read_unlock();

	return i->file;

}

fs/notify/dnotify/dnotify.c

+1 −4
Original line number Diff line number Diff line
@@ -16,7 +16,6 @@ 
#include <linux/security.h>

#include <linux/spinlock.h>

#include <linux/slab.h>

#include <linux/fdtable.h>

#include <linux/fsnotify_backend.h>



static int dir_notify_enable __read_mostly = 1;
@@ -347,9 +346,7 @@ int fcntl_dirnotify(int fd, struct file *filp, unsigned int arg) 
		new_fsn_mark = NULL;

	}



	rcu_read_lock();

	f = lookup_fdget_rcu(fd);

	rcu_read_unlock();

	f = fget_raw(fd);



	/* if (f != filp) means that we lost a race and another task/thread

	 * actually closed the fd we are still playing with before we grabbed

fs/proc/fd.c

+3 −9
Original line number Diff line number Diff line
@@ -116,9 +116,7 @@ static bool tid_fd_mode(struct task_struct *task, unsigned fd, fmode_t *mode) 
{

	struct file *file;



	rcu_read_lock();

	file = task_lookup_fdget_rcu(task, fd);

	rcu_read_unlock();

	file = fget_task(task, fd);

	if (file) {

		*mode = file->f_mode;

		fput(file);
@@ -258,19 +256,17 @@ static int proc_readfd_common(struct file *file, struct dir_context *ctx, 
	if (!dir_emit_dots(file, ctx))

		goto out;



	rcu_read_lock();

	for (fd = ctx->pos - 2;; fd++) {

		struct file *f;

		struct fd_data data;

		char name[10 + 1];

		unsigned int len;



		f = task_lookup_next_fdget_rcu(p, &fd);

		f = fget_task_next(p, &fd);

		ctx->pos = fd + 2LL;

		if (!f)

			break;

		data.mode = f->f_mode;

		rcu_read_unlock();

		fput(f);

		data.fd = fd;
@@ -278,11 +274,9 @@ static int proc_readfd_common(struct file *file, struct dir_context *ctx, 
		if (!proc_fill_cache(file, ctx,

				     name, len, instantiate, p,

				     &data))

			goto out;

			break;

		cond_resched();

		rcu_read_lock();

	}

	rcu_read_unlock();

out:

	put_task_struct(p);

	return 0;