[RFC] Lock free fd lookup

From: Ravikiran G Thirumalai
Date: Tue Jul 13 2004 - 23:59:34 EST

This makes use of the lockfree refcounting infrastructure (see earlier
posting today) to make files_struct.fd[] lookup lockfree. This is carrying
forward work done by Maneesh and Dipankar earlier.

With the lockfree fd lookup patch, tiobench performance increases by 13%
for sequential reads, 21 % for random reads on a 4 processor pIII xeon.

Comments welcome.

Thanks,
Kiran


diff -ruN -X dontdiff linux-2.6.6/arch/mips/kernel/irixioctl.c files_struct-2.6.6/arch/mips/kernel/irixioctl.c
--- linux-2.6.6/arch/mips/kernel/irixioctl.c 2004-05-10 08:02:53.000000000 +0530
+++ files_struct-2.6.6/arch/mips/kernel/irixioctl.c 2004-05-14 12:53:40.000000000 +0530
@@ -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>
@@ -33,15 +34,15 @@
struct file *filp;
struct tty_struct *ttyp = NULL;

- spin_lock(&current->files->file_lock);
- filp = fcheck(fd);
+ rcu_read_lock();
+ filp = fcheck_rcu(fd);
if(filp && filp->private_data) {
ttyp = (struct tty_struct *) filp->private_data;

if(ttyp->magic != TTY_MAGIC)
ttyp =NULL;
}
- spin_unlock(&current->files->file_lock);
+ rcu_read_unlock();
return ttyp;
}

diff -ruN -X dontdiff linux-2.6.6/arch/sparc64/solaris/ioctl.c files_struct-2.6.6/arch/sparc64/solaris/ioctl.c
--- linux-2.6.6/arch/sparc64/solaris/ioctl.c 2004-05-10 08:02:38.000000000 +0530
+++ files_struct-2.6.6/arch/sparc64/solaris/ioctl.c 2004-05-14 12:53:40.000000000 +0530
@@ -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>
@@ -291,15 +292,15 @@
{
struct inode *ino;
/* I wonder which of these tests are superfluous... --patrik */
- spin_lock(&current->files->file_lock);
+ rcu_read_lock();
if (! current->files->fd[fd] ||
! current->files->fd[fd]->f_dentry ||
! (ino = current->files->fd[fd]->f_dentry->d_inode) ||
! ino->i_sock) {
- 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 */
diff -ruN -X dontdiff linux-2.6.6/arch/sparc64/solaris/timod.c files_struct-2.6.6/arch/sparc64/solaris/timod.c
--- linux-2.6.6/arch/sparc64/solaris/timod.c 2004-05-10 08:02:28.000000000 +0530
+++ files_struct-2.6.6/arch/sparc64/solaris/timod.c 2004-05-14 12:53:40.000000000 +0530
@@ -143,9 +143,14 @@
static void timod_wake_socket(unsigned int fd)
{
struct socket *sock;
+ struct file *filp;

SOLD("wakeing socket");
- sock = SOCKET_I(current->files->fd[fd]->f_dentry->d_inode);
+ if (!( filp = fcheck(fd))) {
+ SOLD("BAD FD");
+ return;
+ }
+ sock = SOCKET_I(filp->f_dentry->d_inode);
wake_up_interruptible(&sock->wait);
read_lock(&sock->sk->sk_callback_lock);
if (sock->fasync_list && !test_bit(SOCK_ASYNC_WAITDATA, &sock->flags))
@@ -157,9 +162,14 @@
static void timod_queue(unsigned int fd, struct T_primsg *it)
{
struct sol_socket_struct *sock;
+ struct file *filp;

SOLD("queuing primsg");
- sock = (struct sol_socket_struct *)current->files->fd[fd]->private_data;
+ if (!( filp = fcheck(fd))) {
+ SOLD("BAD FD");
+ return;
+ }
+ sock = (struct sol_socket_struct *)filp->private_data;
it->next = sock->pfirst;
sock->pfirst = it;
if (!sock->plast)
@@ -171,9 +181,14 @@
static void timod_queue_end(unsigned int fd, struct T_primsg *it)
{
struct sol_socket_struct *sock;
+ struct file *filp;

SOLD("queuing primsg at end");
- sock = (struct sol_socket_struct *)current->files->fd[fd]->private_data;
+ if (!( filp = fcheck(fd))) {
+ SOLD("BAD FD");
+ return;
+ }
+ sock = (struct sol_socket_struct *)filp->private_data;
it->next = NULL;
if (sock->plast)
sock->plast->next = it;
@@ -351,7 +366,10 @@
(int (*)(int, unsigned long *))SYS(socketcall);
int (*sys_sendto)(int, void *, size_t, unsigned, struct sockaddr *, int) =
(int (*)(int, void *, size_t, unsigned, struct sockaddr *, int))SYS(sendto);
- filp = current->files->fd[fd];
+
+ if (!(filp = fcheck(fd)))
+ return -EBADF;
+
ino = filp->f_dentry->d_inode;
sock = (struct sol_socket_struct *)filp->private_data;
SOLD("entry");
@@ -632,7 +650,10 @@

SOLD("entry");
SOLDD(("%u %p %d %p %p %d %p %d\n", fd, ctl_buf, ctl_maxlen, ctl_len, data_buf, data_maxlen, data_len, *flags_p));
- filp = current->files->fd[fd];
+
+ if (!(filp = fcheck(fd)))
+ return -EBADF;
+
ino = filp->f_dentry->d_inode;
sock = (struct sol_socket_struct *)filp->private_data;
SOLDD(("%p %p\n", sock->pfirst, sock->pfirst ? sock->pfirst->next : NULL));
@@ -848,7 +869,7 @@
lock_kernel();
if(fd >= NR_OPEN) goto out;

- filp = current->files->fd[fd];
+ filp = fcheck(fd);
if(!filp) goto out;

ino = filp->f_dentry->d_inode;
@@ -915,7 +936,7 @@
lock_kernel();
if(fd >= NR_OPEN) goto out;

- filp = current->files->fd[fd];
+ filp = fcheck(fd);
if(!filp) goto out;

ino = filp->f_dentry->d_inode;
diff -ruN -X dontdiff linux-2.6.6/drivers/char/tty_io.c files_struct-2.6.6/drivers/char/tty_io.c
--- linux-2.6.6/drivers/char/tty_io.c 2004-05-10 08:02:39.000000000 +0530
+++ files_struct-2.6.6/drivers/char/tty_io.c 2004-05-14 12:53:50.000000000 +0530
@@ -1936,9 +1936,9 @@
}
task_lock(p);
if (p->files) {
- spin_lock(&p->files->file_lock);
+ rcu_read_lock();
for (i=0; i < p->files->max_fds; i++) {
- filp = fcheck_files(p->files, i);
+ filp = fcheck_files_rcu(p->files, i);
if (!filp)
continue;
if (filp->f_op->read == tty_read &&
@@ -1950,7 +1950,7 @@
break;
}
}
- spin_unlock(&p->files->file_lock);
+ rcu_read_unlock();
}
task_unlock(p);
}
diff -ruN -X dontdiff linux-2.6.6/drivers/net/ppp_generic.c files_struct-2.6.6/drivers/net/ppp_generic.c
--- linux-2.6.6/drivers/net/ppp_generic.c 2004-05-10 08:03:20.000000000 +0530
+++ files_struct-2.6.6/drivers/net/ppp_generic.c 2004-05-14 12:53:50.000000000 +0530
@@ -46,6 +46,7 @@
#include <linux/rwsem.h>
#include <linux/stddef.h>
#include <linux/device.h>
+#include <linux/refcount.h>
#include <net/slhc_vj.h>
#include <asm/atomic.h>

@@ -525,12 +526,12 @@
if (file == ppp->owner)
ppp_shutdown_interface(ppp);
}
- if (atomic_read(&file->f_count) <= 2) {
+ if (refcount_read(&file->f_count) <= 2) {
ppp_release(inode, file);
err = 0;
} else
printk(KERN_DEBUG "PPPIOCDETACH file->f_count=%d\n",
- atomic_read(&file->f_count));
+ refcount_read(&file->f_count));
return err;
}

diff -ruN -X dontdiff linux-2.6.6/fs/affs/file.c files_struct-2.6.6/fs/affs/file.c
--- linux-2.6.6/fs/affs/file.c 2004-05-10 08:02:29.000000000 +0530
+++ files_struct-2.6.6/fs/affs/file.c 2004-05-14 12:53:50.000000000 +0530
@@ -62,7 +62,7 @@
static int
affs_file_open(struct inode *inode, struct file *filp)
{
- if (atomic_read(&filp->f_count) != 1)
+ if (refcount_read(&filp->f_count) != 1)
return 0;
pr_debug("AFFS: open(%d)\n", AFFS_I(inode)->i_opencnt);
AFFS_I(inode)->i_opencnt++;
@@ -72,7 +72,7 @@
static int
affs_file_release(struct inode *inode, struct file *filp)
{
- if (atomic_read(&filp->f_count) != 0)
+ if (refcount_read(&filp->f_count) != 0)
return 0;
pr_debug("AFFS: release(%d)\n", AFFS_I(inode)->i_opencnt);
AFFS_I(inode)->i_opencnt--;
diff -ruN -X dontdiff linux-2.6.6/fs/aio.c files_struct-2.6.6/fs/aio.c
--- linux-2.6.6/fs/aio.c 2004-05-10 08:02:29.000000000 +0530
+++ files_struct-2.6.6/fs/aio.c 2004-05-14 12:53:50.000000000 +0530
@@ -480,7 +480,7 @@
static int __aio_put_req(struct kioctx *ctx, struct kiocb *req)
{
dprintk(KERN_DEBUG "aio_put(%p): f_count=%d\n",
- req, atomic_read(&req->ki_filp->f_count));
+ req, refcount_read(&req->ki_filp->f_count));

req->ki_users --;
if (unlikely(req->ki_users < 0))
@@ -494,7 +494,7 @@
/* Must be done under the lock to serialise against cancellation.
* Call this aio_fput as it duplicates fput via the fput_work.
*/
- if (unlikely(atomic_dec_and_test(&req->ki_filp->f_count))) {
+ if (unlikely(refcount_put(&req->ki_filp->f_count))) {
get_ioctx(ctx);
spin_lock(&fput_lock);
list_add(&req->ki_list, &fput_head);
diff -ruN -X dontdiff linux-2.6.6/fs/fcntl.c files_struct-2.6.6/fs/fcntl.c
--- linux-2.6.6/fs/fcntl.c 2004-05-10 08:02:53.000000000 +0530
+++ files_struct-2.6.6/fs/fcntl.c 2004-05-14 12:53:50.000000000 +0530
@@ -34,9 +34,9 @@
{
struct files_struct *files = current->files;
int res;
- spin_lock(&files->file_lock);
+ rcu_read_lock();
res = FD_ISSET(fd, files->close_on_exec);
- spin_unlock(&files->file_lock);
+ rcu_read_unlock();
return res;
}

@@ -138,7 +138,7 @@
if (fd >= 0) {
FD_SET(fd, files->open_fds);
FD_CLR(fd, files->close_on_exec);
- spin_unlock(&files->file_lock);
+ spin_unlock(&files->file_lock);
fd_install(fd, file);
} else {
spin_unlock(&files->file_lock);
@@ -183,6 +183,7 @@
goto out_fput;

files->fd[newfd] = file;
+ wmb();
FD_SET(newfd, files->open_fds);
FD_CLR(newfd, files->close_on_exec);
spin_unlock(&files->file_lock);
diff -ruN -X dontdiff linux-2.6.6/fs/file.c files_struct-2.6.6/fs/file.c
--- linux-2.6.6/fs/file.c 2004-05-10 08:02:00.000000000 +0530
+++ files_struct-2.6.6/fs/file.c 2004-05-14 12:53:50.000000000 +0530
@@ -14,7 +14,20 @@
#include <linux/file.h>

#include <asm/bitops.h>
+#include <linux/rcupdate.h>

+struct rcu_fd_array {
+ struct rcu_head rh;
+ struct file **array;
+ int nfds;
+};
+
+struct rcu_fd_set {
+ struct rcu_head rh;
+ fd_set *openset;
+ fd_set *execset;
+ int nfds;
+};

/*
* Allocate an fd array, using kmalloc or vmalloc.
@@ -49,6 +62,13 @@
vfree(array);
}

+static void fd_array_callback(struct rcu_head *rcu)
+{
+ struct rcu_fd_array *a = container_of(rcu, struct rcu_fd_array, rh);
+ free_fd_array(a->array, a->nfds);
+ kfree(a);
+}
+
/*
* Expand the fd array in the files_struct. Called with the files
* spinlock held for write.
@@ -56,8 +76,9 @@

int expand_fd_array(struct files_struct *files, int nr)
{
- struct file **new_fds;
- int error, nfds;
+ struct file **new_fds = NULL;
+ int error, nfds = 0;
+ struct rcu_fd_array *arg = NULL;


error = -EMFILE;
@@ -89,18 +110,17 @@

error = -ENOMEM;
new_fds = alloc_fd_array(nfds);
+ arg = (struct rcu_fd_array *) kmalloc(sizeof(*arg), GFP_KERNEL);
+
spin_lock(&files->file_lock);
- if (!new_fds)
+ if (!new_fds || !arg)
goto out;

/* Copy the existing array and install the new pointer */

if (nfds > files->max_fds) {
- struct file **old_fds;
- int i;
-
- old_fds = xchg(&files->fd, new_fds);
- i = xchg(&files->max_fds, nfds);
+ struct file **old_fds = files->fd;
+ int i = files->max_fds;

/* Don't copy/clear the array if we are creating a new
fd array for fork() */
@@ -109,19 +129,35 @@
/* clear the remainder of the array */
memset(&new_fds[i], 0,
(nfds-i) * sizeof(struct file *));
-
- spin_unlock(&files->file_lock);
- free_fd_array(old_fds, i);
- spin_lock(&files->file_lock);
}
+
+ smp_wmb();
+ files->fd = new_fds;
+ smp_wmb();
+ files->max_fds = nfds;
+
+ if (i) {
+ arg->array = old_fds;
+ arg->nfds = i;
+ call_rcu(&arg->rh, (void (*)(void *))fd_array_callback,
+ &arg->rh);
+ } else
+ kfree(arg);
} else {
/* Somebody expanded the array while we slept ... */
spin_unlock(&files->file_lock);
free_fd_array(new_fds, nfds);
+ kfree(arg);
spin_lock(&files->file_lock);
}
- error = 0;
+
+ return 0;
out:
+ if (new_fds)
+ free_fd_array(new_fds, nfds);
+ if (arg)
+ kfree(arg);
+
return error;
}

@@ -153,6 +189,14 @@
vfree(array);
}

+static void fd_set_callback (struct rcu_head *rcu)
+{
+ struct rcu_fd_set *a = container_of(rcu, struct rcu_fd_set, rh);
+ free_fdset(a->openset, a->nfds);
+ free_fdset(a->execset, a->nfds);
+ kfree(a);
+}
+
/*
* Expand the fdset in the files_struct. Called with the files spinlock
* held for write.
@@ -161,6 +205,7 @@
{
fd_set *new_openset = 0, *new_execset = 0;
int error, nfds = 0;
+ struct rcu_fd_set *arg = NULL;

error = -EMFILE;
if (files->max_fdset >= NR_OPEN || nr >= NR_OPEN)
@@ -183,35 +228,43 @@
error = -ENOMEM;
new_openset = alloc_fdset(nfds);
new_execset = alloc_fdset(nfds);
+ arg = (struct rcu_fd_set *) kmalloc(sizeof(*arg), GFP_ATOMIC);
spin_lock(&files->file_lock);
- if (!new_openset || !new_execset)
+ if (!new_openset || !new_execset || !arg)
goto out;

error = 0;

/* Copy the existing tables and install the new pointers */
if (nfds > files->max_fdset) {
- int i = files->max_fdset / (sizeof(unsigned long) * 8);
- int count = (nfds - files->max_fdset) / 8;
+ fd_set *old_openset = files->open_fds;
+ fd_set *old_execset = files->close_on_exec;
+ int old_nfds = files->max_fdset;
+ int i = old_nfds / (sizeof(unsigned long) * 8);
+ int count = (nfds - old_nfds) / 8;

/*
* Don't copy the entire array if the current fdset is
* not yet initialised.
*/
if (i) {
- memcpy (new_openset, files->open_fds, files->max_fdset/8);
- memcpy (new_execset, files->close_on_exec, files->max_fdset/8);
+ memcpy (new_openset, old_openset, old_nfds/8);
+ memcpy (new_execset, old_execset, old_nfds/8);
memset (&new_openset->fds_bits[i], 0, count);
memset (&new_execset->fds_bits[i], 0, count);
}

- nfds = xchg(&files->max_fdset, nfds);
- new_openset = xchg(&files->open_fds, new_openset);
- new_execset = xchg(&files->close_on_exec, new_execset);
- spin_unlock(&files->file_lock);
- free_fdset (new_openset, nfds);
- free_fdset (new_execset, nfds);
- spin_lock(&files->file_lock);
+ smp_wmb();
+ files->open_fds = new_openset;
+ files->close_on_exec = new_execset;
+ smp_wmb();
+ files->max_fdset = nfds;
+
+ arg->openset = old_openset;
+ arg->execset = old_execset;
+ arg->nfds = nfds;
+ call_rcu(&arg->rh, (void (*)(void *))fd_set_callback, &arg->rh);
+
return 0;
}
/* Somebody expanded the array while we slept ... */
@@ -222,6 +275,8 @@
free_fdset(new_openset, nfds);
if (new_execset)
free_fdset(new_execset, nfds);
+ if (arg)
+ kfree(arg);
spin_lock(&files->file_lock);
return error;
}
diff -ruN -X dontdiff linux-2.6.6/fs/file_table.c files_struct-2.6.6/fs/file_table.c
--- linux-2.6.6/fs/file_table.c 2004-05-10 08:01:59.000000000 +0530
+++ files_struct-2.6.6/fs/file_table.c 2004-05-14 14:05:22.000000000 +0530
@@ -14,6 +14,7 @@
#include <linux/fs.h>
#include <linux/security.h>
#include <linux/eventpoll.h>
+#include <linux/rcupdate.h>
#include <linux/mount.h>
#include <linux/cdev.h>

@@ -54,11 +55,17 @@
spin_unlock_irqrestore(&filp_count_lock, flags);
}

-static inline void file_free(struct file *f)
+static inline void file_free_rcu(void *arg)
{
+ struct file *f = arg;
kmem_cache_free(filp_cachep, f);
}

+static inline void file_free(struct file *f)
+{
+ call_rcu(&f->f_rcuhead, file_free_rcu, f);
+}
+
/* Find an unused file structure and return a pointer to it.
* Returns NULL, if there are no more free file structures or
* we run out of memory.
@@ -81,7 +88,7 @@
goto fail;
}
eventpoll_init_file(f);
- atomic_set(&f->f_count, 1);
+ refcount_init(&f->f_count);
f->f_uid = current->fsuid;
f->f_gid = current->fsgid;
f->f_owner.lock = RW_LOCK_UNLOCKED;
@@ -118,7 +125,7 @@
eventpoll_init_file(filp);
filp->f_flags = flags;
filp->f_mode = (flags+1) & O_ACCMODE;
- atomic_set(&filp->f_count, 1);
+ refcount_init(&filp->f_count);
filp->f_dentry = dentry;
filp->f_mapping = dentry->d_inode->i_mapping;
filp->f_uid = current->fsuid;
@@ -154,7 +161,7 @@

void fastcall fput(struct file *file)
{
- if (atomic_dec_and_test(&file->f_count))
+ if (refcount_put(&file->f_count))
__fput(file);
}

@@ -197,11 +204,16 @@
struct file *file;
struct files_struct *files = current->files;

- spin_lock(&files->file_lock);
- file = fcheck_files(files, fd);
- if (file)
- get_file(file);
- spin_unlock(&files->file_lock);
+ rcu_read_lock();
+ file = fcheck_files_rcu(files, fd);
+ if (file) {
+ if (!refcount_get_rcu(&file->f_count)) {
+ /* File object ref couldn't be taken */
+ rcu_read_unlock();
+ return NULL;
+ }
+ }
+ rcu_read_unlock();
return file;
}

@@ -223,21 +235,25 @@
if (likely((atomic_read(&files->count) == 1))) {
file = fcheck_files(files, fd);
} else {
- spin_lock(&files->file_lock);
- file = fcheck_files(files, fd);
+ rcu_read_lock();
+ file = fcheck_files_rcu(files, fd);
if (file) {
- get_file(file);
- *fput_needed = 1;
+ if (refcount_get_rcu(&file->f_count))
+ *fput_needed = 1;
+ else
+ /* Didn't get the reference, someone's freed */
+ file = NULL;
}
- spin_unlock(&files->file_lock);
+ rcu_read_unlock();
}
+
return file;
}


void put_filp(struct file *file)
{
- if (atomic_dec_and_test(&file->f_count)) {
+ if (refcount_put(&file->f_count)) {
security_file_free(file);
file_kill(file);
file_free(file);
diff -ruN -X dontdiff linux-2.6.6/fs/open.c files_struct-2.6.6/fs/open.c
--- linux-2.6.6/fs/open.c 2004-05-10 08:01:59.000000000 +0530
+++ files_struct-2.6.6/fs/open.c 2004-05-14 12:53:50.000000000 +0530
@@ -1028,7 +1028,9 @@
filp = files->fd[fd];
if (!filp)
goto out_unlock;
- files->fd[fd] = NULL;
+ files->fd[fd] = NULL;
+ /* Need to make it conistent with open_fds in __put_unused_fd() */
+ smp_wmb();
FD_CLR(fd, files->close_on_exec);
__put_unused_fd(files, fd);
spin_unlock(&files->file_lock);
diff -ruN -X dontdiff linux-2.6.6/fs/proc/base.c files_struct-2.6.6/fs/proc/base.c
--- linux-2.6.6/fs/proc/base.c 2004-05-10 08:02:52.000000000 +0530
+++ files_struct-2.6.6/fs/proc/base.c 2004-05-14 12:53:50.000000000 +0530
@@ -28,6 +28,7 @@
#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>
@@ -191,16 +192,16 @@

files = get_files_struct(task);
if (files) {
- spin_lock(&files->file_lock);
- file = fcheck_files(files, fd);
+ rcu_read_lock();
+ file = fcheck_files_rcu(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;
@@ -805,15 +806,15 @@
files = get_files_struct(p);
if (!files)
goto out;
- spin_lock(&files->file_lock);
+ rcu_read_lock();
for (fd = filp->f_pos-2;
fd < files->max_fds;
fd++, filp->f_pos++) {
unsigned int i,j;

- if (!fcheck_files(files, fd))
+ if (!fcheck_files_rcu(files, fd))
continue;
- spin_unlock(&files->file_lock);
+ rcu_read_unlock();

j = NUMBUF;
i = fd;
@@ -825,12 +826,12 @@

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:
@@ -1003,9 +1004,9 @@

files = get_files_struct(task);
if (files) {
- spin_lock(&files->file_lock);
- if (fcheck_files(files, fd)) {
- spin_unlock(&files->file_lock);
+ rcu_read_lock();
+ if (fcheck_files_rcu(files, fd)) {
+ rcu_read_unlock();
put_files_struct(files);
if (task_dumpable(task)) {
inode->i_uid = task->euid;
@@ -1017,7 +1018,7 @@
security_task_to_inode(task, inode);
return 1;
}
- spin_unlock(&files->file_lock);
+ rcu_read_unlock();
put_files_struct(files);
}
d_drop(dentry);
@@ -1109,15 +1110,15 @@
if (!files)
goto out_unlock;
inode->i_mode = S_IFLNK;
- spin_lock(&files->file_lock);
- file = fcheck_files(files, fd);
+ rcu_read_lock();
+ file = fcheck_files_rcu(files, fd);
if (!file)
goto out_unlock2;
if (file->f_mode & 1)
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;
@@ -1127,7 +1128,7 @@
return NULL;

out_unlock2:
- spin_unlock(&files->file_lock);
+ rcu_read_unlock();
put_files_struct(files);
out_unlock:
iput(inode);
diff -ruN -X dontdiff linux-2.6.6/fs/select.c files_struct-2.6.6/fs/select.c
--- linux-2.6.6/fs/select.c 2004-05-10 08:01:59.000000000 +0530
+++ files_struct-2.6.6/fs/select.c 2004-05-14 12:53:50.000000000 +0530
@@ -21,6 +21,7 @@
#include <linux/personality.h> /* for STICKY_TIMEOUTS */
#include <linux/file.h>
#include <linux/fs.h>
+#include <linux/rcupdate.h>

#include <asm/uaccess.h>

@@ -131,13 +132,16 @@
static int max_select_fd(unsigned long n, fd_set_bits *fds)
{
unsigned long *open_fds;
+ fd_set *open_fdset;
unsigned long set;
int max;

/* handle last in-complete long-word first */
set = ~(~0UL << (n & (__NFDBITS-1)));
n /= __NFDBITS;
- open_fds = current->files->open_fds->fds_bits+n;
+ open_fdset = current->files->open_fds;
+ smp_read_barrier_depends();
+ open_fds = open_fdset->fds_bits+n;
max = 0;
if (set) {
set &= BITS(fds, n);
@@ -184,9 +188,9 @@
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;
diff -ruN -X dontdiff linux-2.6.6/include/linux/file.h files_struct-2.6.6/include/linux/file.h
--- linux-2.6.6/include/linux/file.h 2004-05-10 08:03:22.000000000 +0530
+++ files_struct-2.6.6/include/linux/file.h 2004-05-14 12:53:50.000000000 +0530
@@ -9,6 +9,7 @@
#include <linux/posix_types.h>
#include <linux/compiler.h>
#include <linux/spinlock.h>
+#include <linux/rcupdate.h>

/*
* The default fd array needs to be at least BITS_PER_LONG,
@@ -69,10 +70,26 @@
return file;
}

+/* Need Proper read barriers if fd_array is being indexed lockfree */
+static inline struct file * fcheck_files_rcu(struct files_struct *files, unsigned int fd)
+{
+ struct file * file = NULL;
+
+ if (fd < files->max_fds) {
+ struct file ** fd_array;
+ smp_rmb();
+ fd_array = files->fd;
+ smp_read_barrier_depends();
+ file = fd_array[fd];
+ }
+ return file;
+}
+
/*
* Check whether the specified fd has an open file.
*/
#define fcheck(fd) fcheck_files(current->files, fd)
+#define fcheck_rcu(fd) fcheck_files_rcu(current->files, fd)

extern void FASTCALL(fd_install(unsigned int fd, struct file * file));

diff -ruN -X dontdiff linux-2.6.6/include/linux/fs.h files_struct-2.6.6/include/linux/fs.h
--- linux-2.6.6/include/linux/fs.h 2004-05-10 08:02:26.000000000 +0530
+++ files_struct-2.6.6/include/linux/fs.h 2004-05-14 12:53:50.000000000 +0530
@@ -19,6 +19,7 @@
#include <linux/cache.h>
#include <linux/radix-tree.h>
#include <linux/kobject.h>
+#include <linux/refcount.h>
#include <asm/atomic.h>
#include <linux/audit.h>

@@ -555,7 +556,7 @@
struct dentry *f_dentry;
struct vfsmount *f_vfsmnt;
struct file_operations *f_op;
- atomic_t f_count;
+ refcount_t f_count;
unsigned int f_flags;
mode_t f_mode;
loff_t f_pos;
@@ -576,13 +577,14 @@
spinlock_t f_ep_lock;
#endif /* #ifdef CONFIG_EPOLL */
struct address_space *f_mapping;
+ struct rcu_head f_rcuhead;
};
extern spinlock_t files_lock;
#define file_list_lock() spin_lock(&files_lock);
#define file_list_unlock() spin_unlock(&files_lock);

-#define get_file(x) atomic_inc(&(x)->f_count)
-#define file_count(x) atomic_read(&(x)->f_count)
+#define get_file(x) refcount_get(&(x)->f_count)
+#define file_count(x) refcount_read(&(x)->f_count)

/* Initialize and open a private file and allocate its security structure. */
extern int open_private_file(struct file *, struct dentry *, int);
diff -ruN -X dontdiff linux-2.6.6/kernel/fork.c files_struct-2.6.6/kernel/fork.c
--- linux-2.6.6/kernel/fork.c 2004-05-10 08:02:00.000000000 +0530
+++ files_struct-2.6.6/kernel/fork.c 2004-05-14 12:53:50.000000000 +0530
@@ -30,6 +30,7 @@
#include <linux/syscalls.h>
#include <linux/jiffies.h>
#include <linux/futex.h>
+#include <linux/rcupdate.h>
#include <linux/ptrace.h>
#include <linux/mount.h>
#include <linux/audit.h>
@@ -627,10 +628,12 @@
static int count_open_files(struct files_struct *files, int size)
{
int i;
+ fd_set *open_fds = files->open_fds;

+ smp_read_barrier_depends();
/* Find the last open fd */
for (i = size/(8*sizeof(long)); i > 0; ) {
- if (files->open_fds->fds_bits[--i])
+ if (open_fds->fds_bits[--i])
break;
}
i = (i+1) * 8 * sizeof(long);
@@ -660,6 +663,14 @@
* This works because we cache current->files (old) as oldf. Don't
* break this.
*/
+
+ /*
+ * We don't have oldf readlock, but even if the old fdset gets
+ * grown now, we'll only copy upto "size" fds
+ */
+ size = oldf->max_fdset;
+ smp_rmb();
+
tsk->files = NULL;
error = -ENOMEM;
newf = kmem_cache_alloc(files_cachep, SLAB_KERNEL);
@@ -676,9 +687,6 @@
newf->open_fds = &newf->open_fds_init;
newf->fd = &newf->fd_array[0];

- /* We don't yet have the oldf readlock, but even if the old
- fdset gets grown now, we'll only copy up to "size" fds */
- size = oldf->max_fdset;
if (size > __FD_SETSIZE) {
newf->max_fdset = 0;
spin_lock(&newf->file_lock);
@@ -687,7 +695,7 @@
if (error)
goto out_release;
}
- spin_lock(&oldf->file_lock);
+ rcu_read_lock();

open_files = count_open_files(oldf, size);

@@ -698,7 +706,7 @@
*/
nfds = NR_OPEN_DEFAULT;
if (open_files > nfds) {
- spin_unlock(&oldf->file_lock);
+ rcu_read_unlock();
newf->max_fds = 0;
spin_lock(&newf->file_lock);
error = expand_fd_array(newf, open_files-1);
@@ -706,10 +714,11 @@
if (error)
goto out_release;
nfds = newf->max_fds;
- spin_lock(&oldf->file_lock);
+ rcu_read_lock();
}

old_fds = oldf->fd;
+ smp_read_barrier_depends();
new_fds = newf->fd;

memcpy(newf->open_fds->fds_bits, oldf->open_fds->fds_bits, open_files/8);
@@ -721,7 +730,7 @@
get_file(f);
*new_fds++ = f;
}
- spin_unlock(&oldf->file_lock);
+ rcu_read_unlock();

/* compute the remainder to be cleared */
size = (newf->max_fds - open_files) * sizeof(struct file *);
diff -ruN -X dontdiff linux-2.6.6/net/ipv4/netfilter/ipt_owner.c files_struct-2.6.6/net/ipv4/netfilter/ipt_owner.c
--- linux-2.6.6/net/ipv4/netfilter/ipt_owner.c 2004-05-10 08:03:20.000000000 +0530
+++ files_struct-2.6.6/net/ipv4/netfilter/ipt_owner.c 2004-05-14 12:53:50.000000000 +0530
@@ -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>
@@ -35,17 +36,17 @@
task_lock(p);
files = p->files;
if(files) {
- spin_lock(&files->file_lock);
+ rcu_read_lock();
for (i=0; i < files->max_fds; i++) {
- if (fcheck_files(files, i) ==
+ if (fcheck_files_rcu(files, i) ==
skb->sk->sk_socket->file) {
- spin_unlock(&files->file_lock);
+ rcu_read_unlock();
task_unlock(p);
read_unlock(&tasklist_lock);
return 1;
}
}
- spin_unlock(&files->file_lock);
+ rcu_read_unlock();
}
task_unlock(p);
} while_each_thread(g, p);
@@ -67,17 +68,17 @@
task_lock(p);
files = p->files;
if(files) {
- spin_lock(&files->file_lock);
+ rcu_read_lock();
for (i=0; i < files->max_fds; i++) {
- if (fcheck_files(files, i) ==
+ if (fcheck_files_rcu(files, i) ==
skb->sk->sk_socket->file) {
- spin_unlock(&files->file_lock);
+ rcu_read_unlock();
task_unlock(p);
read_unlock(&tasklist_lock);
return 1;
}
}
- spin_unlock(&files->file_lock);
+ rcu_read_unlock();
}
task_unlock(p);
out:
@@ -101,14 +102,14 @@
task_lock(p);
files = p->files;
if (files) {
- spin_lock(&files->file_lock);
+ rcu_read_lock();
for (i=0; i < files->max_fds; i++) {
- if (fcheck_files(files, i) == file) {
+ if (fcheck_files_rcu(files, i) == file) {
found = 1;
break;
}
}
- spin_unlock(&files->file_lock);
+ rcu_read_unlock();
}
task_unlock(p);
if (found)
diff -ruN -X dontdiff linux-2.6.6/net/ipv6/netfilter/ip6t_owner.c files_struct-2.6.6/net/ipv6/netfilter/ip6t_owner.c
--- linux-2.6.6/net/ipv6/netfilter/ip6t_owner.c 2004-05-10 08:03:13.000000000 +0530
+++ files_struct-2.6.6/net/ipv6/netfilter/ip6t_owner.c 2004-05-14 12:53:50.000000000 +0530
@@ -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>
@@ -34,16 +35,16 @@
task_lock(p);
files = p->files;
if(files) {
- spin_lock(&files->file_lock);
+ rcu_read_lock();
for (i=0; i < files->max_fds; i++) {
- if (fcheck_files(files, i) == skb->sk->sk_socket->file) {
- spin_unlock(&files->file_lock);
+ if (fcheck_files_rcu(files, i) == skb->sk->sk_socket->file) {
+ rcu_read_unlock();
task_unlock(p);
read_unlock(&tasklist_lock);
return 1;
}
}
- spin_unlock(&files->file_lock);
+ rcu_read_unlock();
}
task_unlock(p);
out:
@@ -67,14 +68,14 @@
task_lock(p);
files = p->files;
if (files) {
- spin_lock(&files->file_lock);
+ rcu_read_lock();
for (i=0; i < files->max_fds; i++) {
- if (fcheck_files(files, i) == file) {
+ if (fcheck_files_rcu(files, i) == file) {
found = 1;
break;
}
}
- spin_unlock(&files->file_lock);
+ rcu_read_unlock();
}
task_unlock(p);
if (found)

-
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