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

[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
......@@ -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;
}
......
......@@ -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 */
......
......@@ -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);
......
......@@ -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;
}
......
......@@ -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);
......
......@@ -22,6 +22,7 @@
#include <linux/personality.h> /* for STICKY_TIMEOUTS */
#include <linux/file.h>
#include <linux/fs.h>
#include <linux/rcupdate.h>
#include <asm/uaccess.h>
......@@ -185,9 +186,9 @@ int do_select(int n, fd_set_bits *fds, long *timeout)
int retval, i;
long __timeout = *timeout;
spin_lock(&current->files->file_lock);
rcu_read_lock();
retval = max_select_fd(n, fds);
spin_unlock(&current->files->file_lock);
rcu_read_unlock();
if (retval < 0)
return retval;
......@@ -329,8 +330,10 @@ sys_select(int n, fd_set __user *inp, fd_set __user *outp, fd_set __user *exp, s
goto out_nofds;
/* max_fdset can increase, so grab it once to avoid race */
rcu_read_lock();
fdt = files_fdtable(current->files);
max_fdset = fdt->max_fdset;
rcu_read_unlock();
if (n > max_fdset)
n = max_fdset;
......@@ -469,10 +472,14 @@ asmlinkage long sys_poll(struct pollfd __user * ufds, unsigned int nfds, long ti
struct poll_list *head;
struct poll_list *walk;
struct fdtable *fdt;
int max_fdset;
/* Do a sanity check on nfds ... */
rcu_read_lock();
fdt = files_fdtable(current->files);
if (nfds > fdt->max_fdset && nfds > OPEN_MAX)
max_fdset = fdt->max_fdset;
rcu_read_unlock();
if (nfds > max_fdset && nfds > OPEN_MAX)
return -EINVAL;
if (timeout) {
......
......@@ -11,6 +11,7 @@
#include <linux/module.h>
#include <linux/skbuff.h>
#include <linux/file.h>
#include <linux/rcupdate.h>
#include <net/sock.h>
#include <linux/netfilter_ipv4/ipt_owner.h>
......
......@@ -11,6 +11,7 @@
#include <linux/module.h>
#include <linux/skbuff.h>
#include <linux/file.h>
#include <linux/rcupdate.h>
#include <net/sock.h>
#include <linux/netfilter_ipv6/ip6t_owner.h>
......
......@@ -1652,7 +1652,7 @@ static inline void flush_unauthorized_files(struct files_struct * files)
continue;
}
if (devnull) {
atomic_inc(&devnull->f_count);
rcuref_inc(&devnull->f_count);
} else {
devnull = dentry_open(dget(selinux_null), mntget(selinuxfs_mount), O_RDWR);
if (!devnull) {
......
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