Commit b835996f authored by Dipankar Sarma's avatar Dipankar Sarma Committed by Linus Torvalds
Browse files

[PATCH] files: lock-free fd look-up 



With the use of RCU in files structure, the look-up of files using fds can now
be lock-free.  The lookup is protected by rcu_read_lock()/rcu_read_unlock().
This patch changes the readers to use lock-free lookup.

Signed-off-by: default avatarManeesh Soni <maneesh@in.ibm.com>
Signed-off-by: default avatarRavikiran Thirumalai <kiran_th@gmail.com>
Signed-off-by: default avatarDipankar Sarma <dipankar@in.ibm.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent ab2af1f5

arch/mips/kernel/irixioctl.c

+3 −2
Original line number Diff line number Diff line
@@ -14,6 +14,7 @@ 
#include <linux/syscalls.h>

#include <linux/tty.h>

#include <linux/file.h>

#include <linux/rcupdate.h>



#include <asm/uaccess.h>

#include <asm/ioctl.h>
@@ -33,7 +34,7 @@ static struct tty_struct *get_tty(int fd) 
	struct file *filp;

	struct tty_struct *ttyp = NULL;



	spin_lock(&current->files->file_lock);

	rcu_read_lock();

	filp = fcheck(fd);

	if(filp && filp->private_data) {

		ttyp = (struct tty_struct *) filp->private_data;
@@ -41,7 +42,7 @@ static struct tty_struct *get_tty(int fd) 
		if(ttyp->magic != TTY_MAGIC)

			ttyp =NULL;

	}

	spin_unlock(&current->files->file_lock);

	rcu_read_unlock();

	return ttyp;

}

arch/sparc64/solaris/ioctl.c

+4 −3
Original line number Diff line number Diff line
@@ -24,6 +24,7 @@ 
#include <linux/netdevice.h>

#include <linux/mtio.h>

#include <linux/time.h>

#include <linux/rcupdate.h>

#include <linux/compat.h>



#include <net/sock.h>
@@ -295,16 +296,16 @@ static inline int solaris_sockmod(unsigned int fd, unsigned int cmd, u32 arg) 
	struct inode *ino;

	struct fdtable *fdt;

	/* I wonder which of these tests are superfluous... --patrik */

	spin_lock(&current->files->file_lock);

	rcu_read_lock();

	fdt = files_fdtable(current->files);

	if (! fdt->fd[fd] ||

	    ! fdt->fd[fd]->f_dentry ||

	    ! (ino = fdt->fd[fd]->f_dentry->d_inode) ||

	    ! S_ISSOCK(ino->i_mode)) {

		spin_unlock(&current->files->file_lock);

		rcu_read_unlock();

		return TBADF;

	}

	spin_unlock(&current->files->file_lock);

	rcu_read_unlock();

	

	switch (cmd & 0xff) {

	case 109: /* SI_SOCKPARAMS */

drivers/char/tty_io.c

+2 −2
Original line number Diff line number Diff line
@@ -2480,7 +2480,7 @@ static void __do_SAK(void *arg) 
		}

		task_lock(p);

		if (p->files) {

			spin_lock(&p->files->file_lock);

			rcu_read_lock();

			fdt = files_fdtable(p->files);

			for (i=0; i < fdt->max_fds; i++) {

				filp = fcheck_files(p->files, i);
@@ -2495,7 +2495,7 @@ static void __do_SAK(void *arg) 
					break;

				}

			}

			spin_unlock(&p->files->file_lock);

			rcu_read_unlock();

		}

		task_unlock(p);

	} while_each_task_pid(session, PIDTYPE_SID, p);

fs/fcntl.c

+2 −2
Original line number Diff line number Diff line
@@ -40,10 +40,10 @@ static inline int get_close_on_exec(unsigned int fd) 
	struct files_struct *files = current->files;

	struct fdtable *fdt;

	int res;

	spin_lock(&files->file_lock);

	rcu_read_lock();

	fdt = files_fdtable(files);

	res = FD_ISSET(fd, fdt->close_on_exec);

	spin_unlock(&files->file_lock);

	rcu_read_unlock();

	return res;

}

fs/proc/base.c

+15 −14
Original line number Diff line number Diff line
@@ -62,6 +62,7 @@ 
#include <linux/namespace.h>

#include <linux/mm.h>

#include <linux/smp_lock.h>

#include <linux/rcupdate.h>

#include <linux/kallsyms.h>

#include <linux/mount.h>

#include <linux/security.h>
@@ -283,16 +284,16 @@ static int proc_fd_link(struct inode *inode, struct dentry **dentry, struct vfsm 


	files = get_files_struct(task);

	if (files) {

		spin_lock(&files->file_lock);

		rcu_read_lock();

		file = fcheck_files(files, fd);

		if (file) {

			*mnt = mntget(file->f_vfsmnt);

			*dentry = dget(file->f_dentry);

			spin_unlock(&files->file_lock);

			rcu_read_unlock();

			put_files_struct(files);

			return 0;

		}

		spin_unlock(&files->file_lock);

		rcu_read_unlock();

		put_files_struct(files);

	}

	return -ENOENT;
@@ -1062,7 +1063,7 @@ static int proc_readfd(struct file * filp, void * dirent, filldir_t filldir) 
			files = get_files_struct(p);

			if (!files)

				goto out;

			spin_lock(&files->file_lock);

			rcu_read_lock();

			fdt = files_fdtable(files);

			for (fd = filp->f_pos-2;

			     fd < fdt->max_fds;
@@ -1071,7 +1072,7 @@ static int proc_readfd(struct file * filp, void * dirent, filldir_t filldir) 


				if (!fcheck_files(files, fd))

					continue;

				spin_unlock(&files->file_lock);

				rcu_read_unlock();



				j = NUMBUF;

				i = fd;
@@ -1083,12 +1084,12 @@ static int proc_readfd(struct file * filp, void * dirent, filldir_t filldir) 


				ino = fake_ino(tid, PROC_TID_FD_DIR + fd);

				if (filldir(dirent, buf+j, NUMBUF-j, fd+2, ino, DT_LNK) < 0) {

					spin_lock(&files->file_lock);

					rcu_read_lock();

					break;

				}

				spin_lock(&files->file_lock);

				rcu_read_lock();

			}

			spin_unlock(&files->file_lock);

			rcu_read_unlock();

			put_files_struct(files);

	}

out:
@@ -1263,9 +1264,9 @@ static int tid_fd_revalidate(struct dentry *dentry, struct nameidata *nd) 


	files = get_files_struct(task);

	if (files) {

		spin_lock(&files->file_lock);

		rcu_read_lock();

		if (fcheck_files(files, fd)) {

			spin_unlock(&files->file_lock);

			rcu_read_unlock();

			put_files_struct(files);

			if (task_dumpable(task)) {

				inode->i_uid = task->euid;
@@ -1277,7 +1278,7 @@ static int tid_fd_revalidate(struct dentry *dentry, struct nameidata *nd) 
			security_task_to_inode(task, inode);

			return 1;

		}

		spin_unlock(&files->file_lock);

		rcu_read_unlock();

		put_files_struct(files);

	}

	d_drop(dentry);
@@ -1369,7 +1370,7 @@ static struct dentry *proc_lookupfd(struct inode * dir, struct dentry * dentry, 
	if (!files)

		goto out_unlock;

	inode->i_mode = S_IFLNK;

	spin_lock(&files->file_lock);

	rcu_read_lock();

	file = fcheck_files(files, fd);

	if (!file)

		goto out_unlock2;
@@ -1377,7 +1378,7 @@ static struct dentry *proc_lookupfd(struct inode * dir, struct dentry * dentry, 
		inode->i_mode |= S_IRUSR | S_IXUSR;

	if (file->f_mode & 2)

		inode->i_mode |= S_IWUSR | S_IXUSR;

	spin_unlock(&files->file_lock);

	rcu_read_unlock();

	put_files_struct(files);

	inode->i_op = &proc_pid_link_inode_operations;

	inode->i_size = 64;
@@ -1387,7 +1388,7 @@ static struct dentry *proc_lookupfd(struct inode * dir, struct dentry * dentry, 
	return NULL;



out_unlock2:

	spin_unlock(&files->file_lock);

	rcu_read_unlock();

	put_files_struct(files);

out_unlock:

	iput(inode);

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