[PATCH] files: break up files struct

In order for the RCU to work, the file table array, sets and their sizes must
be updated atomically.  Instead of ensuring this through too many memory
barriers, we put the arrays and their sizes in a separate structure.  This
patch takes the first step of putting the file table elements in a separate
structure fdtable that is embedded withing files_struct.  It also changes all
the users to refer to the file table using files_fdtable() macro.  Subsequent
applciation of RCU becomes easier after this.

Signed-off-by: Dipankar Sarma <dipankar@in.ibm.com>
Signed-Off-By: David Howells <dhowells@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

arch/alpha/kernel/osf_sys.c

@@ -974,6 +974,7 @@ osf_select(int n, fd_set __user *inp, fd_set __user *outp, fd_set __user *exp,
 	size_t size;
 	long timeout;
 	int ret = -EINVAL;
+	struct fdtable *fdt;
 
 	timeout = MAX_SCHEDULE_TIMEOUT;
 	if (tvp) {
@@ -995,7 +996,8 @@ osf_select(int n, fd_set __user *inp, fd_set __user *outp, fd_set __user *exp,
 		}
 	}
 
-	if (n < 0 || n > current->files->max_fdset)
+	fdt = files_fdtable(current->files);
+	if (n < 0 || n > fdt->max_fdset)
 		goto out_nofds;
 
 	/*

arch/ia64/kernel/perfmon.c

@@ -38,6 +38,7 @@
 #include <linux/pagemap.h>
 #include <linux/mount.h>
 #include <linux/bitops.h>
+#include <linux/rcupdate.h>
 
 #include <asm/errno.h>
 #include <asm/intrinsics.h>
@@ -2217,15 +2218,17 @@ static void
 pfm_free_fd(int fd, struct file *file)
 {
 	struct files_struct *files = current->files;
+	struct fdtable *fdt = files_fdtable(files);
 
 	/* 
 	 * there ie no fd_uninstall(), so we do it here
 	 */
 	spin_lock(&files->file_lock);
-        files->fd[fd] = NULL;
+	rcu_assign_pointer(fdt->fd[fd], NULL);
 	spin_unlock(&files->file_lock);
 
-	if (file) put_filp(file);
+	if (file)
+		put_filp(file);
 	put_unused_fd(fd);
 }
 

arch/sparc64/solaris/ioctl.c

@@ -293,11 +293,13 @@ static struct module_info {
 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);
-	if (! current->files->fd[fd] ||
-	    ! current->files->fd[fd]->f_dentry ||
-	    ! (ino = current->files->fd[fd]->f_dentry->d_inode) ||
+	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);
 		return TBADF;

drivers/char/tty_io.c

@@ -2454,6 +2454,7 @@ static void __do_SAK(void *arg)
 	int		i;
 	struct file	*filp;
 	struct tty_ldisc *disc;
+	struct fdtable *fdt;
 	
 	if (!tty)
 		return;
@@ -2480,7 +2481,8 @@ static void __do_SAK(void *arg)
 		task_lock(p);
 		if (p->files) {
 			spin_lock(&p->files->file_lock);
-			for (i=0; i < p->files->max_fds; i++) {
+			fdt = files_fdtable(p->files);
+			for (i=0; i < fdt->max_fds; i++) {
 				filp = fcheck_files(p->files, i);
 				if (!filp)
 					continue;

fs/exec.c

@@ -798,6 +798,7 @@ no_thread_group:
 static inline void flush_old_files(struct files_struct * files)
 {
 	long j = -1;
+	struct fdtable *fdt;
 
 	spin_lock(&files->file_lock);
 	for (;;) {
@@ -805,12 +806,13 @@ static inline void flush_old_files(struct files_struct * files)
 
 		j++;
 		i = j * __NFDBITS;
-		if (i >= files->max_fds || i >= files->max_fdset)
+		fdt = files_fdtable(files);
+		if (i >= fdt->max_fds || i >= fdt->max_fdset)
 			break;
-		set = files->close_on_exec->fds_bits[j];
+		set = fdt->close_on_exec->fds_bits[j];
 		if (!set)
 			continue;
-		files->close_on_exec->fds_bits[j] = 0;
+		fdt->close_on_exec->fds_bits[j] = 0;
 		spin_unlock(&files->file_lock);
 		for ( ; set ; i++,set >>= 1) {
 			if (set & 1) {

fs/fcntl.c

@@ -24,20 +24,24 @@
 void fastcall 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)
-		FD_SET(fd, files->close_on_exec);
+		FD_SET(fd, fdt->close_on_exec);
 	else
-		FD_CLR(fd, files->close_on_exec);
+		FD_CLR(fd, fdt->close_on_exec);
 	spin_unlock(&files->file_lock);
 }
 
 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);
-	res = FD_ISSET(fd, files->close_on_exec);
+	fdt = files_fdtable(files);
+	res = FD_ISSET(fd, fdt->close_on_exec);
 	spin_unlock(&files->file_lock);
 	return res;
 }
@@ -54,24 +58,26 @@ static int locate_fd(struct files_struct *files,
 	unsigned int newfd;
 	unsigned int start;
 	int error;
+	struct fdtable *fdt;
 
 	error = -EINVAL;
 	if (orig_start >= current->signal->rlim[RLIMIT_NOFILE].rlim_cur)
 		goto out;
 
+	fdt = files_fdtable(files);
 repeat:
 	/*
 	 * Someone might have closed fd's in the range
-	 * orig_start..files->next_fd
+	 * orig_start..fdt->next_fd
 	 */
 	start = orig_start;
-	if (start < files->next_fd)
-		start = files->next_fd;
+	if (start < fdt->next_fd)
+		start = fdt->next_fd;
 
 	newfd = start;
-	if (start < files->max_fdset) {
-		newfd = find_next_zero_bit(files->open_fds->fds_bits,
-			files->max_fdset, start);
+	if (start < fdt->max_fdset) {
+		newfd = find_next_zero_bit(fdt->open_fds->fds_bits,
+			fdt->max_fdset, start);
 	}
 	
 	error = -EMFILE;
@@ -89,8 +95,8 @@ repeat:
 	if (error)
 		goto repeat;
 
-	if (start <= files->next_fd)
-		files->next_fd = newfd + 1;
+	if (start <= fdt->next_fd)
+		fdt->next_fd = newfd + 1;
 	
 	error = newfd;
 	
@@ -101,13 +107,16 @@ out:
 static int dupfd(struct file *file, unsigned int start)
 {
 	struct files_struct * files = current->files;
+	struct fdtable *fdt;
 	int fd;
 
 	spin_lock(&files->file_lock);
 	fd = locate_fd(files, file, start);
 	if (fd >= 0) {
-		FD_SET(fd, files->open_fds);
-		FD_CLR(fd, files->close_on_exec);
+		/* locate_fd() may have expanded fdtable, load the ptr */
+		fdt = files_fdtable(files);
+		FD_SET(fd, fdt->open_fds);
+		FD_CLR(fd, fdt->close_on_exec);
 		spin_unlock(&files->file_lock);
 		fd_install(fd, file);
 	} else {
@@ -123,6 +132,7 @@ asmlinkage long sys_dup2(unsigned int oldfd, unsigned int newfd)
 	int err = -EBADF;
 	struct file * file, *tofree;
 	struct files_struct * files = current->files;
+	struct fdtable *fdt;
 
 	spin_lock(&files->file_lock);
 	if (!(file = fcheck(oldfd)))
@@ -148,13 +158,14 @@ asmlinkage long sys_dup2(unsigned int oldfd, unsigned int newfd)
 
 	/* Yes. It's a race. In user space. Nothing sane to do */
 	err = -EBUSY;
-	tofree = files->fd[newfd];
-	if (!tofree && FD_ISSET(newfd, files->open_fds))
+	fdt = files_fdtable(files);
+	tofree = fdt->fd[newfd];
+	if (!tofree && FD_ISSET(newfd, fdt->open_fds))
 		goto out_fput;
 
-	files->fd[newfd] = file;
-	FD_SET(newfd, files->open_fds);
-	FD_CLR(newfd, files->close_on_exec);
+	fdt->fd[newfd] = file;
+	FD_SET(newfd, fdt->open_fds);
+	FD_CLR(newfd, fdt->close_on_exec);
 	spin_unlock(&files->file_lock);
 
 	if (tofree)

fs/file.c

@@ -59,13 +59,15 @@ static int expand_fd_array(struct files_struct *files, int nr)
 {
 	struct file **new_fds;
 	int error, nfds;
+	struct fdtable *fdt;
 
 	
 	error = -EMFILE;
-	if (files->max_fds >= NR_OPEN || nr >= NR_OPEN)
+	fdt = files_fdtable(files);
+	if (fdt->max_fds >= NR_OPEN || nr >= NR_OPEN)
 		goto out;
 
-	nfds = files->max_fds;
+	nfds = fdt->max_fds;
 	spin_unlock(&files->file_lock);
 
 	/* 
@@ -95,13 +97,14 @@ static int expand_fd_array(struct files_struct *files, int nr)
 		goto out;
 
 	/* Copy the existing array and install the new pointer */
+	fdt = files_fdtable(files);
 
-	if (nfds > files->max_fds) {
+	if (nfds > fdt->max_fds) {
 		struct file **old_fds;
 		int i;
 		
-		old_fds = xchg(&files->fd, new_fds);
-		i = xchg(&files->max_fds, nfds);
+		old_fds = xchg(&fdt->fd, new_fds);
+		i = xchg(&fdt->max_fds, nfds);
 
 		/* Don't copy/clear the array if we are creating a new
 		   fd array for fork() */
@@ -164,12 +167,14 @@ static int expand_fdset(struct files_struct *files, int nr)
 {
 	fd_set *new_openset = NULL, *new_execset = NULL;
 	int error, nfds = 0;
+	struct fdtable *fdt;
 
 	error = -EMFILE;
-	if (files->max_fdset >= NR_OPEN || nr >= NR_OPEN)
+	fdt = files_fdtable(files);
+	if (fdt->max_fdset >= NR_OPEN || nr >= NR_OPEN)
 		goto out;
 
-	nfds = files->max_fdset;
+	nfds = fdt->max_fdset;
 	spin_unlock(&files->file_lock);
 
 	/* Expand to the max in easy steps */
@@ -193,24 +198,25 @@ static int expand_fdset(struct files_struct *files, int nr)
 	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;
+	fdt = files_fdtable(files);
+	if (nfds > fdt->max_fdset) {
+		int i = fdt->max_fdset / (sizeof(unsigned long) * 8);
+		int count = (nfds - fdt->max_fdset) / 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, fdt->open_fds, fdt->max_fdset/8);
+			memcpy (new_execset, fdt->close_on_exec, fdt->max_fdset/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);
+		nfds = xchg(&fdt->max_fdset, nfds);
+		new_openset = xchg(&fdt->open_fds, new_openset);
+		new_execset = xchg(&fdt->close_on_exec, new_execset);
 		spin_unlock(&files->file_lock);
 		free_fdset (new_openset, nfds);
 		free_fdset (new_execset, nfds);
@@ -237,13 +243,15 @@ out:
 int expand_files(struct files_struct *files, int nr)
 {
 	int err, expand = 0;
+	struct fdtable *fdt;
 
-	if (nr >= files->max_fdset) {
+	fdt = files_fdtable(files);
+	if (nr >= fdt->max_fdset) {
 		expand = 1;
 		if ((err = expand_fdset(files, nr)))
 			goto out;
 	}
-	if (nr >= files->max_fds) {
+	if (nr >= fdt->max_fds) {
 		expand = 1;
 		if ((err = expand_fd_array(files, nr)))
 			goto out;

fs/locks.c

@@ -2198,21 +2198,23 @@ void steal_locks(fl_owner_t from)
 {
 	struct files_struct *files = current->files;
 	int i, j;
+	struct fdtable *fdt;
 
 	if (from == files)
 		return;
 
 	lock_kernel();
 	j = 0;
+	fdt = files_fdtable(files);
 	for (;;) {
 		unsigned long set;
 		i = j * __NFDBITS;
-		if (i >= files->max_fdset || i >= files->max_fds)
+		if (i >= fdt->max_fdset || i >= fdt->max_fds)
 			break;
-		set = files->open_fds->fds_bits[j++];
+		set = fdt->open_fds->fds_bits[j++];
 		while (set) {
 			if (set & 1) {
-				struct file *file = files->fd[i];
+				struct file *file = fdt->fd[i];
 				if (file)
 					__steal_locks(file, from);
 			}

fs/open.c

@@ -842,14 +842,16 @@ int get_unused_fd(void)
 {
 	struct files_struct * files = current->files;
 	int fd, error;
+	struct fdtable *fdt;
 
   	error = -EMFILE;
 	spin_lock(&files->file_lock);
 
 repeat:
- 	fd = find_next_zero_bit(files->open_fds->fds_bits, 
-				files->max_fdset, 
-				files->next_fd);
+	fdt = files_fdtable(files);
+ 	fd = find_next_zero_bit(fdt->open_fds->fds_bits,
+				fdt->max_fdset,
+				fdt->next_fd);
 
 	/*
 	 * N.B. For clone tasks sharing a files structure, this test
@@ -872,14 +874,14 @@ repeat:
 		goto repeat;
 	}
 
-	FD_SET(fd, files->open_fds);
-	FD_CLR(fd, files->close_on_exec);
-	files->next_fd = fd + 1;
+	FD_SET(fd, fdt->open_fds);
+	FD_CLR(fd, fdt->close_on_exec);
+	fdt->next_fd = fd + 1;
 #if 1
 	/* Sanity check */
-	if (files->fd[fd] != NULL) {
+	if (fdt->fd[fd] != NULL) {
 		printk(KERN_WARNING "get_unused_fd: slot %d not NULL!\n", fd);
-		files->fd[fd] = NULL;
+		fdt->fd[fd] = NULL;
 	}
 #endif
 	error = fd;
@@ -893,9 +895,10 @@ EXPORT_SYMBOL(get_unused_fd);
 
 static inline void __put_unused_fd(struct files_struct *files, unsigned int fd)
 {
-	__FD_CLR(fd, files->open_fds);
-	if (fd < files->next_fd)
-		files->next_fd = fd;
+	struct fdtable *fdt = files_fdtable(files);
+	__FD_CLR(fd, fdt->open_fds);
+	if (fd < fdt->next_fd)
+		fdt->next_fd = fd;
 }
 
 void fastcall put_unused_fd(unsigned int fd)
@@ -924,10 +927,12 @@ EXPORT_SYMBOL(put_unused_fd);
 void fastcall fd_install(unsigned int fd, struct file * file)
 {
 	struct files_struct *files = current->files;
+	struct fdtable *fdt;
 	spin_lock(&files->file_lock);
-	if (unlikely(files->fd[fd] != NULL))
+	fdt = files_fdtable(files);
+	if (unlikely(fdt->fd[fd] != NULL))
 		BUG();
-	files->fd[fd] = file;
+	fdt->fd[fd] = file;
 	spin_unlock(&files->file_lock);
 }
 
@@ -1010,15 +1015,17 @@ asmlinkage long sys_close(unsigned int fd)
 {
 	struct file * filp;
 	struct files_struct *files = current->files;
+	struct fdtable *fdt;
 
 	spin_lock(&files->file_lock);
-	if (fd >= files->max_fds)
+	fdt = files_fdtable(files);
+	if (fd >= fdt->max_fds)
 		goto out_unlock;
-	filp = files->fd[fd];
+	filp = fdt->fd[fd];
 	if (!filp)
 		goto out_unlock;
-	files->fd[fd] = NULL;
-	FD_CLR(fd, files->close_on_exec);
+	fdt->fd[fd] = NULL;
+	FD_CLR(fd, fdt->close_on_exec);
 	__put_unused_fd(files, fd);
 	spin_unlock(&files->file_lock);
 	return filp_close(filp, files);

fs/proc/array.c

@@ -159,6 +159,7 @@ static inline char * task_state(struct task_struct *p, char *buffer)
 {
 	struct group_info *group_info;
 	int g;
+	struct fdtable *fdt = NULL;
 
 	read_lock(&tasklist_lock);
 	buffer += sprintf(buffer,
@@ -179,10 +180,12 @@ static inline char * task_state(struct task_struct *p, char *buffer)
 		p->gid, p->egid, p->sgid, p->fsgid);
 	read_unlock(&tasklist_lock);
 	task_lock(p);
+	if (p->files)
+		fdt = files_fdtable(p->files);
 	buffer += sprintf(buffer,
 		"FDSize:\t%d\n"
 		"Groups:\t",
-		p->files ? p->files->max_fds : 0);
+		fdt ? fdt->max_fds : 0);
 
 	group_info = p->group_info;
 	get_group_info(group_info);

fs/proc/base.c

@@ -1039,6 +1039,7 @@ static int proc_readfd(struct file * filp, void * dirent, filldir_t filldir)
 	int retval;
 	char buf[NUMBUF];
 	struct files_struct * files;
+	struct fdtable *fdt;
 
 	retval = -ENOENT;
 	if (!pid_alive(p))
@@ -1062,8 +1063,9 @@ static int proc_readfd(struct file * filp, void * dirent, filldir_t filldir)
 			if (!files)
 				goto out;
 			spin_lock(&files->file_lock);
+			fdt = files_fdtable(files);
 			for (fd = filp->f_pos-2;
-			     fd < files->max_fds;
+			     fd < fdt->max_fds;
 			     fd++, filp->f_pos++) {
 				unsigned int i,j;
 

fs/select.c

@@ -132,11 +132,13 @@ static int max_select_fd(unsigned long n, fd_set_bits *fds)
 	unsigned long *open_fds;
 	unsigned long set;
 	int max;
+	struct fdtable *fdt;
 
 	/* handle last in-complete long-word first */
 	set = ~(~0UL << (n & (__NFDBITS-1)));
 	n /= __NFDBITS;
-	open_fds = current->files->open_fds->fds_bits+n;
+	fdt = files_fdtable(current->files);
+	open_fds = fdt->open_fds->fds_bits+n;
 	max = 0;
 	if (set) {
 		set &= BITS(fds, n);
@@ -299,6 +301,7 @@ sys_select(int n, fd_set __user *inp, fd_set __user *outp, fd_set __user *exp, s
 	char *bits;
 	long timeout;
 	int ret, size, max_fdset;
+	struct fdtable *fdt;
 
 	timeout = MAX_SCHEDULE_TIMEOUT;
 	if (tvp) {
@@ -326,7 +329,8 @@ 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 */
-	max_fdset = current->files->max_fdset;
+	fdt = files_fdtable(current->files);
+	max_fdset = fdt->max_fdset;
 	if (n > max_fdset)
 		n = max_fdset;
 
@@ -464,9 +468,11 @@ asmlinkage long sys_poll(struct pollfd __user * ufds, unsigned int nfds, long ti
  	unsigned int i;
 	struct poll_list *head;
  	struct poll_list *walk;
+	struct fdtable *fdt;
 
 	/* Do a sanity check on nfds ... */
-	if (nfds > current->files->max_fdset && nfds > OPEN_MAX)
+	fdt = files_fdtable(current->files);
+	if (nfds > fdt->max_fdset && nfds > OPEN_MAX)
 		return -EINVAL;
 
 	if (timeout) {

include/linux/file.h

@@ -16,23 +16,29 @@
  */
 #define NR_OPEN_DEFAULT BITS_PER_LONG
 
+struct fdtable {
+	unsigned int max_fds;
+	int max_fdset;
+	int next_fd;
+	struct file ** fd;      /* current fd array */
+	fd_set *close_on_exec;
+	fd_set *open_fds;
+};
+
 /*
  * Open file table structure
  */
 struct files_struct {
         atomic_t count;
         spinlock_t file_lock;     /* Protects all the below members.  Nests inside tsk->alloc_lock */
-        int max_fds;
-        int max_fdset;
-        int next_fd;
-        struct file ** fd;      /* current fd array */
-        fd_set *close_on_exec;
-        fd_set *open_fds;
+	struct fdtable fdtab;
         fd_set close_on_exec_init;
         fd_set open_fds_init;
         struct file * fd_array[NR_OPEN_DEFAULT];
 };
 
+#define files_fdtable(files) (&(files)->fdtab)
+
 extern void FASTCALL(__fput(struct file *));
 extern void FASTCALL(fput(struct file *));
 
@@ -63,9 +69,10 @@ extern int expand_files(struct files_struct *, int nr);
 static inline struct file * fcheck_files(struct files_struct *files, unsigned int fd)
 {
 	struct file * file = NULL;
+	struct fdtable *fdt = files_fdtable(files);
 
-	if (fd < files->max_fds)
-		file = files->fd[fd];
+	if (fd < fdt->max_fds)
+		file = fdt->fd[fd];
 	return file;
 }
 

include/linux/init_task.h

@@ -3,16 +3,21 @@
 
 #include <linux/file.h>
 
-#define INIT_FILES \
-{ 							\
-	.count		= ATOMIC_INIT(1), 		\
-	.file_lock	= SPIN_LOCK_UNLOCKED, 		\
+#define INIT_FDTABLE \
+{							\
 	.max_fds	= NR_OPEN_DEFAULT, 		\
 	.max_fdset	= __FD_SETSIZE, 		\
 	.next_fd	= 0, 				\
 	.fd		= &init_files.fd_array[0], 	\
 	.close_on_exec	= &init_files.close_on_exec_init, \
 	.open_fds	= &init_files.open_fds_init, 	\
+}
+
+#define INIT_FILES \
+{ 							\
+	.count		= ATOMIC_INIT(1), 		\
+	.file_lock	= SPIN_LOCK_UNLOCKED, 		\
+	.fdtab		= INIT_FDTABLE,			\
 	.close_on_exec_init = { { 0, } }, 		\
 	.open_fds_init	= { { 0, } }, 			\
 	.fd_array	= { NULL, } 			\

kernel/exit.c

@@ -368,17 +368,19 @@ EXPORT_SYMBOL(daemonize);
 static inline void close_files(struct files_struct * files)
 {
 	int i, j;
+	struct fdtable *fdt;
 
 	j = 0;
+	fdt = files_fdtable(files);
 	for (;;) {
 		unsigned long set;
 		i = j * __NFDBITS;
-		if (i >= files->max_fdset || i >= files->max_fds)
+		if (i >= fdt->max_fdset || i >= fdt->max_fds)
 			break;
-		set = files->open_fds->fds_bits[j++];
+		set = fdt->open_fds->fds_bits[j++];
 		while (set) {
 			if (set & 1) {
-				struct file * file = xchg(&files->fd[i], NULL);
+				struct file * file = xchg(&fdt->fd[i], NULL);
 				if (file)
 					filp_close(file, files);
 			}
@@ -403,16 +405,19 @@ struct files_struct *get_files_struct(struct task_struct *task)
 
 void fastcall put_files_struct(struct files_struct *files)
 {
+	struct fdtable *fdt;
+
 	if (atomic_dec_and_test(&files->count)) {
 		close_files(files);
 		/*
 		 * Free the fd and fdset arrays if we expanded them.
 		 */
-		if (files->fd != &files->fd_array[0])
-			free_fd_array(files->fd, files->max_fds);
-		if (files->max_fdset > __FD_SETSIZE) {
-			free_fdset(files->open_fds, files->max_fdset);
-			free_fdset(files->close_on_exec, files->max_fdset);
+		fdt = files_fdtable(files);
+		if (fdt->fd != &files->fd_array[0])
+			free_fd_array(fdt->fd, fdt->max_fds);
+		if (fdt->max_fdset > __FD_SETSIZE) {
+			free_fdset(fdt->open_fds, fdt->max_fdset);
+			free_fdset(fdt->close_on_exec, fdt->max_fdset);
 		}
 		kmem_cache_free(files_cachep, files);
 	}

kernel/fork.c

@@ -568,21 +568,47 @@ static inline int copy_fs(unsigned long clone_flags, struct task_struct * tsk)
 static int count_open_files(struct files_struct *files, int size)
 {
 	int i;
+	struct fdtable *fdt;
 
 	/* Find the last open fd */
+	fdt = files_fdtable(files);
 	for (i = size/(8*sizeof(long)); i > 0; ) {
-		if (files->open_fds->fds_bits[--i])
+		if (fdt->open_fds->fds_bits[--i])
 			break;
 	}
 	i = (i+1) * 8 * sizeof(long);
 	return i;
 }
 
+static struct files_struct *alloc_files(void)
+{
+	struct files_struct *newf;
+	struct fdtable *fdt;
+
+	newf = kmem_cache_alloc(files_cachep, SLAB_KERNEL);
+	if (!newf)
+		goto out;
+
+	atomic_set(&newf->count, 1);
+
+	spin_lock_init(&newf->file_lock);
+	fdt = files_fdtable(newf);
+	fdt->next_fd = 0;
+	fdt->max_fds = NR_OPEN_DEFAULT;
+	fdt->max_fdset = __FD_SETSIZE;
+	fdt->close_on_exec = &newf->close_on_exec_init;
+	fdt->open_fds = &newf->open_fds_init;
+	fdt->fd = &newf->fd_array[0];
+out:
+	return newf;
+}
+
 static int copy_files(unsigned long clone_flags, struct task_struct * tsk)
 {
 	struct files_struct *oldf, *newf;
 	struct file **old_fds, **new_fds;
 	int open_files, size, i, error = 0, expand;
+	struct fdtable *old_fdt, *new_fdt;
 
 	/*
 	 * A background process may not have any files ...
@@ -603,35 +629,27 @@ static int copy_files(unsigned long clone_flags, struct task_struct * tsk)
 	 */
 	tsk->files = NULL;
 	error = -ENOMEM;
-	newf = kmem_cache_alloc(files_cachep, SLAB_KERNEL);
-	if (!newf) 
+	newf = alloc_files();
+	if (!newf)
 		goto out;
 
-	atomic_set(&newf->count, 1);
-
-	spin_lock_init(&newf->file_lock);
-	newf->next_fd	    = 0;
-	newf->max_fds	    = NR_OPEN_DEFAULT;
-	newf->max_fdset	    = __FD_SETSIZE;
-	newf->close_on_exec = &newf->close_on_exec_init;
-	newf->open_fds	    = &newf->open_fds_init;
-	newf->fd	    = &newf->fd_array[0];
-
 	spin_lock(&oldf->file_lock);
-
-	open_files = count_open_files(oldf, oldf->max_fdset);
+	old_fdt = files_fdtable(oldf);
+	new_fdt = files_fdtable(newf);
+	size = old_fdt->max_fdset;
+	open_files = count_open_files(oldf, old_fdt->max_fdset);
 	expand = 0;
 
 	/*
 	 * Check whether we need to allocate a larger fd array or fd set.
 	 * Note: we're not a clone task, so the open count won't  change.
 	 */
-	if (open_files > newf->max_fdset) {
-		newf->max_fdset = 0;
+	if (open_files > new_fdt->max_fdset) {
+		new_fdt->max_fdset = 0;
 		expand = 1;
 	}
-	if (open_files > newf->max_fds) {
-		newf->max_fds = 0;
+	if (open_files > new_fdt->max_fds) {
+		new_fdt->max_fds = 0;
 		expand = 1;
 	}
 
@@ -646,11 +664,11 @@ static int copy_files(unsigned long clone_flags, struct task_struct * tsk)
 		spin_lock(&oldf->file_lock);
 	}
 
-	old_fds = oldf->fd;
-	new_fds = newf->fd;
+	old_fds = old_fdt->fd;
+	new_fds = new_fdt->fd;
 
-	memcpy(newf->open_fds->fds_bits, oldf->open_fds->fds_bits, open_files/8);
-	memcpy(newf->close_on_exec->fds_bits, oldf->close_on_exec->fds_bits, open_files/8);
+	memcpy(new_fdt->open_fds->fds_bits, old_fdt->open_fds->fds_bits, open_files/8);
+	memcpy(new_fdt->close_on_exec->fds_bits, old_fdt->close_on_exec->fds_bits, open_files/8);
 
 	for (i = open_files; i != 0; i--) {
 		struct file *f = *old_fds++;
@@ -663,24 +681,24 @@ static int copy_files(unsigned long clone_flags, struct task_struct * tsk)
 			 * is partway through open().  So make sure that this
 			 * fd is available to the new process.
 			 */
-			FD_CLR(open_files - i, newf->open_fds);
+			FD_CLR(open_files - i, new_fdt->open_fds);
 		}
 		*new_fds++ = f;
 	}
 	spin_unlock(&oldf->file_lock);
 
 	/* compute the remainder to be cleared */
-	size = (newf->max_fds - open_files) * sizeof(struct file *);
+	size = (new_fdt->max_fds - open_files) * sizeof(struct file *);
 
 	/* This is long word aligned thus could use a optimized version */ 
 	memset(new_fds, 0, size); 
 
-	if (newf->max_fdset > open_files) {
-		int left = (newf->max_fdset-open_files)/8;
+	if (new_fdt->max_fdset > open_files) {
+		int left = (new_fdt->max_fdset-open_files)/8;
 		int start = open_files / (8 * sizeof(unsigned long));
 
-		memset(&newf->open_fds->fds_bits[start], 0, left);
-		memset(&newf->close_on_exec->fds_bits[start], 0, left);
+		memset(&new_fdt->open_fds->fds_bits[start], 0, left);
+		memset(&new_fdt->close_on_exec->fds_bits[start], 0, left);
 	}
 
 	tsk->files = newf;
@@ -689,9 +707,9 @@ out:
 	return error;
 
 out_release:
-	free_fdset (newf->close_on_exec, newf->max_fdset);
-	free_fdset (newf->open_fds, newf->max_fdset);
-	free_fd_array(newf->fd, newf->max_fds);
+	free_fdset (new_fdt->close_on_exec, new_fdt->max_fdset);
+	free_fdset (new_fdt->open_fds, new_fdt->max_fdset);
+	free_fd_array(new_fdt->fd, new_fdt->max_fds);
 	kmem_cache_free(files_cachep, newf);
 	goto out;
 }

security/selinux/hooks.c

@@ -1594,6 +1594,7 @@ static inline void flush_unauthorized_files(struct files_struct * files)
 	struct avc_audit_data ad;
 	struct file *file, *devnull = NULL;
 	struct tty_struct *tty = current->signal->tty;
+	struct fdtable *fdt;
 	long j = -1;
 
 	if (tty) {
@@ -1627,9 +1628,10 @@ static inline void flush_unauthorized_files(struct files_struct * files)
 
 		j++;
 		i = j * __NFDBITS;
-		if (i >= files->max_fds || i >= files->max_fdset)
+		fdt = files_fdtable(files);
+		if (i >= fdt->max_fds || i >= fdt->max_fdset)
 			break;
-		set = files->open_fds->fds_bits[j];
+		set = fdt->open_fds->fds_bits[j];
 		if (!set)
 			continue;
 		spin_unlock(&files->file_lock);