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[PATCH] files: files struct with RCU 

Patch to eliminate struct files_struct.file_lock spinlock on the reader side
and use rcu refcounting rcuref_xxx api for the f_count refcounter.  The
updates to the fdtable are done by allocating a new fdtable structure and
setting files->fdt to point to the new structure.  The fdtable structure is
protected by RCU thereby allowing lock-free lookup.  For fd arrays/sets that
are vmalloced, we use keventd to free them since RCU callbacks can't sleep.  A
global list of fdtable to be freed is not scalable, so we use a per-cpu list.
If keventd is already handling the current cpu's work, we use a timer to defer
queueing of that work.

Since the last publication, this patch has been re-written to avoid using
explicit memory barriers and use rcu_assign_pointer(), rcu_dereference()
premitives instead.  This required that the fd information is kept in a
separate structure (fdtable) and updated atomically.

Signed-off-by: Dipankar Sarma <dipankar@in.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Dipankar Sarma 2005-09-09 13:04:13 -07:00 committed by Linus Torvalds
parent 6e72ad2c58
commit ab2af1f500
10 changed files with 354 additions and 175 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
fs/aio.c
View File

@ -29,6 +29,7 @@
#include <linux/highmem.h>
#include <linux/workqueue.h>
#include <linux/security.h>
#include <linux/rcuref.h>
#include <asm/kmap_types.h>
#include <asm/uaccess.h>
@ -499,7 +500,7 @@ static int __aio_put_req(struct kioctx *ctx, struct kiocb *req)
/* 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(rcuref_dec_and_test(&req->ki_filp->f_count))) {
get_ioctx(ctx);
spin_lock(&fput_lock);
list_add(&req->ki_list, &fput_head);

13
fs/fcntl.c
View File

@ -16,6 +16,7 @@
#include <linux/security.h>
#include <linux/ptrace.h>
#include <linux/signal.h>
#include <linux/rcupdate.h>
#include <asm/poll.h>
#include <asm/siginfo.h>
@ -64,8 +65,8 @@ static int locate_fd(struct files_struct *files,
if (orig_start >= current->signal->rlim[RLIMIT_NOFILE].rlim_cur)
goto out;
fdt = files_fdtable(files);
repeat:
fdt = files_fdtable(files);
/*
* Someone might have closed fd's in the range
* orig_start..fdt->next_fd
@ -95,9 +96,15 @@ static int locate_fd(struct files_struct *files,
if (error)
goto repeat;
/*
* We reacquired files_lock, so we are safe as long as
* we reacquire the fdtable pointer and use it while holding
* the lock, no one can free it during that time.
*/
fdt = files_fdtable(files);
if (start <= fdt->next_fd)
fdt->next_fd = newfd + 1;
error = newfd;
out:
@ -163,7 +170,7 @@ asmlinkage long sys_dup2(unsigned int oldfd, unsigned int newfd)
if (!tofree && FD_ISSET(newfd, fdt->open_fds))
goto out_fput;
fdt->fd[newfd] = file;
rcu_assign_pointer(fdt->fd[newfd], file);
FD_SET(newfd, fdt->open_fds);
FD_CLR(newfd, fdt->close_on_exec);
spin_unlock(&files->file_lock);

407
fs/file.c
View File

@ -13,6 +13,25 @@
#include <linux/vmalloc.h>
#include <linux/file.h>
#include <linux/bitops.h>
#include <linux/interrupt.h>
#include <linux/spinlock.h>
#include <linux/rcupdate.h>
#include <linux/workqueue.h>
struct fdtable_defer {
spinlock_t lock;
struct work_struct wq;
struct timer_list timer;
struct fdtable *next;
};
/*
* We use this list to defer free fdtables that have vmalloced
* sets/arrays. By keeping a per-cpu list, we avoid having to embed
* the work_struct in fdtable itself which avoids a 64 byte (i386) increase in
* this per-task structure.
*/
static DEFINE_PER_CPU(struct fdtable_defer, fdtable_defer_list);
/*
@ -48,85 +67,143 @@ void free_fd_array(struct file **array, int num)
vfree(array);
}
/*
* Expand the fd array in the files_struct. Called with the files
* spinlock held for write.
*/
static int expand_fd_array(struct files_struct *files, int nr)
__releases(files->file_lock)
__acquires(files->file_lock)
static void __free_fdtable(struct fdtable *fdt)
{
int fdset_size, fdarray_size;
fdset_size = fdt->max_fdset / 8;
fdarray_size = fdt->max_fds * sizeof(struct file *);
free_fdset(fdt->open_fds, fdset_size);
free_fdset(fdt->close_on_exec, fdset_size);
free_fd_array(fdt->fd, fdarray_size);
kfree(fdt);
}
static void fdtable_timer(unsigned long data)
{
struct fdtable_defer *fddef = (struct fdtable_defer *)data;
spin_lock(&fddef->lock);
/*
* If someone already emptied the queue return.
*/
if (!fddef->next)
goto out;
if (!schedule_work(&fddef->wq))
mod_timer(&fddef->timer, 5);
out:
spin_unlock(&fddef->lock);
}
static void free_fdtable_work(struct fdtable_defer *f)
{
struct file **new_fds;
int error, nfds;
struct fdtable *fdt;
error = -EMFILE;
fdt = files_fdtable(files);
if (fdt->max_fds >= NR_OPEN || nr >= NR_OPEN)
goto out;
nfds = fdt->max_fds;
spin_unlock(&files->file_lock);
/*
* Expand to the max in easy steps, and keep expanding it until
* we have enough for the requested fd array size.
*/
do {
#if NR_OPEN_DEFAULT < 256
if (nfds < 256)
nfds = 256;
else
#endif
if (nfds < (PAGE_SIZE / sizeof(struct file *)))
nfds = PAGE_SIZE / sizeof(struct file *);
else {
nfds = nfds * 2;
if (nfds > NR_OPEN)
nfds = NR_OPEN;
}
} while (nfds <= nr);
error = -ENOMEM;
new_fds = alloc_fd_array(nfds);
spin_lock(&files->file_lock);
if (!new_fds)
goto out;
/* Copy the existing array and install the new pointer */
fdt = files_fdtable(files);
if (nfds > fdt->max_fds) {
struct file **old_fds;
int i;
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() */
if (i) {
memcpy(new_fds, old_fds, i * sizeof(struct file *));
/* 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);
}
} else {
/* Somebody expanded the array while we slept ... */
spin_unlock(&files->file_lock);
free_fd_array(new_fds, nfds);
spin_lock(&files->file_lock);
spin_lock_bh(&f->lock);
fdt = f->next;
f->next = NULL;
spin_unlock_bh(&f->lock);
while(fdt) {
struct fdtable *next = fdt->next;
__free_fdtable(fdt);
fdt = next;
}
error = 0;
out:
return error;
}
static void free_fdtable_rcu(struct rcu_head *rcu)
{
struct fdtable *fdt = container_of(rcu, struct fdtable, rcu);
int fdset_size, fdarray_size;
struct fdtable_defer *fddef;
BUG_ON(!fdt);
fdset_size = fdt->max_fdset / 8;
fdarray_size = fdt->max_fds * sizeof(struct file *);
if (fdt->free_files) {
/*
* The this fdtable was embedded in the files structure
* and the files structure itself was getting destroyed.
* It is now safe to free the files structure.
*/
kmem_cache_free(files_cachep, fdt->free_files);
return;
}
if (fdt->max_fdset <= __FD_SETSIZE && fdt->max_fds <= NR_OPEN_DEFAULT) {
/*
* The fdtable was embedded
*/
return;
}
if (fdset_size <= PAGE_SIZE && fdarray_size <= PAGE_SIZE) {
kfree(fdt->open_fds);
kfree(fdt->close_on_exec);
kfree(fdt->fd);
kfree(fdt);
} else {
fddef = &get_cpu_var(fdtable_defer_list);
spin_lock(&fddef->lock);
fdt->next = fddef->next;
fddef->next = fdt;
/*
* vmallocs are handled from the workqueue context.
* If the per-cpu workqueue is running, then we
* defer work scheduling through a timer.
*/
if (!schedule_work(&fddef->wq))
mod_timer(&fddef->timer, 5);
spin_unlock(&fddef->lock);
put_cpu_var(fdtable_defer_list);
}
}
void free_fdtable(struct fdtable *fdt)
{
if (fdt->free_files || fdt->max_fdset > __FD_SETSIZE ||
fdt->max_fds > NR_OPEN_DEFAULT)
call_rcu(&fdt->rcu, free_fdtable_rcu);
}
/*
* Expand the fdset in the files_struct. Called with the files spinlock
* held for write.
*/
static void copy_fdtable(struct fdtable *nfdt, struct fdtable *fdt)
{
int i;
int count;
BUG_ON(nfdt->max_fdset < fdt->max_fdset);
BUG_ON(nfdt->max_fds < fdt->max_fds);
/* Copy the existing tables and install the new pointers */
i = fdt->max_fdset / (sizeof(unsigned long) * 8);
count = (nfdt->max_fdset - fdt->max_fdset) / 8;
/*
* Don't copy the entire array if the current fdset is
* not yet initialised.
*/
if (i) {
memcpy (nfdt->open_fds, fdt->open_fds,
fdt->max_fdset/8);
memcpy (nfdt->close_on_exec, fdt->close_on_exec,
fdt->max_fdset/8);
memset (&nfdt->open_fds->fds_bits[i], 0, count);
memset (&nfdt->close_on_exec->fds_bits[i], 0, count);
}
/* Don't copy/clear the array if we are creating a new
fd array for fork() */
if (fdt->max_fds) {
memcpy(nfdt->fd, fdt->fd,
fdt->max_fds * sizeof(struct file *));
/* clear the remainder of the array */
memset(&nfdt->fd[fdt->max_fds], 0,
(nfdt->max_fds - fdt->max_fds) *
sizeof(struct file *));
}
nfdt->next_fd = fdt->next_fd;
}
/*
@ -157,28 +234,21 @@ void free_fdset(fd_set *array, int num)
vfree(array);
}
/*
* Expand the fdset in the files_struct. Called with the files spinlock
* held for write.
*/
static int expand_fdset(struct files_struct *files, int nr)
__releases(file->file_lock)
__acquires(file->file_lock)
static struct fdtable *alloc_fdtable(int nr)
{
fd_set *new_openset = NULL, *new_execset = NULL;
int error, nfds = 0;
struct fdtable *fdt;
struct fdtable *fdt = NULL;
int nfds = 0;
fd_set *new_openset = NULL, *new_execset = NULL;
struct file **new_fds;
error = -EMFILE;
fdt = files_fdtable(files);
if (fdt->max_fdset >= NR_OPEN || nr >= NR_OPEN)
goto out;
fdt = kmalloc(sizeof(*fdt), GFP_KERNEL);
if (!fdt)
goto out;
memset(fdt, 0, sizeof(*fdt));
nfds = fdt->max_fdset;
spin_unlock(&files->file_lock);
/* Expand to the max in easy steps */
do {
nfds = __FD_SETSIZE;
/* Expand to the max in easy steps */
do {
if (nfds < (PAGE_SIZE * 8))
nfds = PAGE_SIZE * 8;
else {
@ -188,50 +258,88 @@ static int expand_fdset(struct files_struct *files, int nr)
}
} while (nfds <= nr);
error = -ENOMEM;
new_openset = alloc_fdset(nfds);
new_execset = alloc_fdset(nfds);
spin_lock(&files->file_lock);
if (!new_openset || !new_execset)
new_openset = alloc_fdset(nfds);
new_execset = alloc_fdset(nfds);
if (!new_openset || !new_execset)
goto out;
fdt->open_fds = new_openset;
fdt->close_on_exec = new_execset;
fdt->max_fdset = nfds;
nfds = NR_OPEN_DEFAULT;
/*
* Expand to the max in easy steps, and keep expanding it until
* we have enough for the requested fd array size.
*/
do {
#if NR_OPEN_DEFAULT < 256
if (nfds < 256)
nfds = 256;
else
#endif
if (nfds < (PAGE_SIZE / sizeof(struct file *)))
nfds = PAGE_SIZE / sizeof(struct file *);
else {
nfds = nfds * 2;
if (nfds > NR_OPEN)
nfds = NR_OPEN;
}
} while (nfds <= nr);
new_fds = alloc_fd_array(nfds);
if (!new_fds)
goto out;
error = 0;
/* Copy the existing tables and install the new pointers */
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, 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(&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);
spin_lock(&files->file_lock);
return 0;
}
/* Somebody expanded the array while we slept ... */
fdt->fd = new_fds;
fdt->max_fds = nfds;
fdt->free_files = NULL;
return fdt;
out:
if (new_openset)
free_fdset(new_openset, nfds);
if (new_execset)
free_fdset(new_execset, nfds);
kfree(fdt);
return NULL;
}
/*
* Expands the file descriptor table - it will allocate a new fdtable and
* both fd array and fdset. It is expected to be called with the
* files_lock held.
*/
static int expand_fdtable(struct files_struct *files, int nr)
__releases(files->file_lock)
__acquires(files->file_lock)
{
int error = 0;
struct fdtable *fdt;
struct fdtable *nfdt = NULL;
spin_unlock(&files->file_lock);
if (new_openset)
free_fdset(new_openset, nfds);
if (new_execset)
free_fdset(new_execset, nfds);
nfdt = alloc_fdtable(nr);
if (!nfdt) {
error = -ENOMEM;
spin_lock(&files->file_lock);
goto out;
}
spin_lock(&files->file_lock);
fdt = files_fdtable(files);
/*
* Check again since another task may have expanded the
* fd table while we dropped the lock
*/
if (nr >= fdt->max_fds || nr >= fdt->max_fdset) {
copy_fdtable(nfdt, fdt);
} else {
/* Somebody expanded while we dropped file_lock */
spin_unlock(&files->file_lock);
__free_fdtable(nfdt);
spin_lock(&files->file_lock);
goto out;
}
rcu_assign_pointer(files->fdt, nfdt);
free_fdtable(fdt);
out:
return error;
}
@ -246,17 +354,36 @@ int expand_files(struct files_struct *files, int nr)
struct fdtable *fdt;
fdt = files_fdtable(files);
if (nr >= fdt->max_fdset) {
expand = 1;
if ((err = expand_fdset(files, nr)))
if (nr >= fdt->max_fdset || nr >= fdt->max_fds) {
if (fdt->max_fdset >= NR_OPEN ||
fdt->max_fds >= NR_OPEN || nr >= NR_OPEN) {
err = -EMFILE;
goto out;
}
if (nr >= fdt->max_fds) {
}
expand = 1;
if ((err = expand_fd_array(files, nr)))
if ((err = expand_fdtable(files, nr)))
goto out;
}
err = expand;
out:
return err;
}
static void __devinit fdtable_defer_list_init(int cpu)
{
struct fdtable_defer *fddef = &per_cpu(fdtable_defer_list, cpu);
spin_lock_init(&fddef->lock);
INIT_WORK(&fddef->wq, (void (*)(void *))free_fdtable_work, fddef);
init_timer(&fddef->timer);
fddef->timer.data = (unsigned long)fddef;
fddef->timer.function = fdtable_timer;
fddef->next = NULL;
}
void __init files_defer_init(void)
{
int i;
/* Really early - can't use for_each_cpu */
for (i = 0; i < NR_CPUS; i++)
fdtable_defer_list_init(i);
}

40
fs/file_table.c
View File

@ -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>
#include <linux/fsnotify.h>
@ -53,9 +54,15 @@ void filp_dtor(void * objp, struct kmem_cache_s *cachep, unsigned long dflags)
spin_unlock_irqrestore(&filp_count_lock, flags);
}
static inline void file_free_rcu(struct rcu_head *head)
{
struct file *f = container_of(head, struct file, f_rcuhead);
kmem_cache_free(filp_cachep, f);
}
static inline void file_free(struct file *f)
{
kmem_cache_free(filp_cachep, f);
call_rcu(&f->f_rcuhead, file_free_rcu);
}
/* Find an unused file structure and return a pointer to it.
@ -110,7 +117,7 @@ EXPORT_SYMBOL(get_empty_filp);
void fastcall fput(struct file *file)
{
if (atomic_dec_and_test(&file->f_count))
if (rcuref_dec_and_test(&file->f_count))
__fput(file);
}
@ -156,11 +163,17 @@ struct file fastcall *fget(unsigned int fd)
struct file *file;
struct files_struct *files = current->files;
spin_lock(&files->file_lock);
rcu_read_lock();
file = fcheck_files(files, fd);
if (file)
get_file(file);
spin_unlock(&files->file_lock);
if (file) {
if (!rcuref_inc_lf(&file->f_count)) {
/* File object ref couldn't be taken */
rcu_read_unlock();
return NULL;
}
}
rcu_read_unlock();
return file;
}
@ -182,21 +195,25 @@ struct file fastcall *fget_light(unsigned int fd, int *fput_needed)
if (likely((atomic_read(&files->count) == 1))) {
file = fcheck_files(files, fd);
} else {
spin_lock(&files->file_lock);
rcu_read_lock();
file = fcheck_files(files, fd);
if (file) {
get_file(file);
*fput_needed = 1;
if (rcuref_inc_lf(&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 (rcuref_dec_and_test(&file->f_count)) {
security_file_free(file);
file_kill(file);
file_free(file);
@ -257,4 +274,5 @@ void __init files_init(unsigned long mempages)
files_stat.max_files = n;
if (files_stat.max_files < NR_FILE)
files_stat.max_files = NR_FILE;
files_defer_init();
}

8
fs/open.c
View File

@ -24,6 +24,7 @@
#include <linux/personality.h>
#include <linux/pagemap.h>
#include <linux/syscalls.h>
#include <linux/rcupdate.h>
#include <asm/unistd.h>
@ -930,9 +931,8 @@ void fastcall fd_install(unsigned int fd, struct file * file)
struct fdtable *fdt;
spin_lock(&files->file_lock);
fdt = files_fdtable(files);
if (unlikely(fdt->fd[fd] != NULL))
BUG();
fdt->fd[fd] = file;
BUG_ON(fdt->fd[fd] != NULL);
rcu_assign_pointer(fdt->fd[fd], file);
spin_unlock(&files->file_lock);
}
@ -1024,7 +1024,7 @@ asmlinkage long sys_close(unsigned int fd)
filp = fdt->fd[fd];
if (!filp)
goto out_unlock;
fdt->fd[fd] = NULL;
rcu_assign_pointer(fdt->fd[fd], NULL);
FD_CLR(fd, fdt->close_on_exec);
__put_unused_fd(files, fd);
spin_unlock(&files->file_lock);

11
include/linux/file.h
View File

@ -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,
@ -23,6 +24,9 @@ struct fdtable {
struct file ** fd; /* current fd array */
fd_set *close_on_exec;
fd_set *open_fds;
struct rcu_head rcu;
struct files_struct *free_files;
struct fdtable *next;
};
/*
@ -31,13 +35,14 @@ struct fdtable {
struct files_struct {
atomic_t count;
spinlock_t file_lock; /* Protects all the below members. Nests inside tsk->alloc_lock */
struct fdtable *fdt;
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)
#define files_fdtable(files) (rcu_dereference((files)->fdt))
extern void FASTCALL(__fput(struct file *));
extern void FASTCALL(fput(struct file *));
@ -65,6 +70,8 @@ extern fd_set *alloc_fdset(int);
extern void free_fdset(fd_set *, int);
extern int expand_files(struct files_struct *, int nr);
extern void free_fdtable(struct fdtable *fdt);
extern void __init files_defer_init(void);
static inline struct file * fcheck_files(struct files_struct *files, unsigned int fd)
{
@ -72,7 +79,7 @@ static inline struct file * fcheck_files(struct files_struct *files, unsigned in
struct fdtable *fdt = files_fdtable(files);
if (fd < fdt->max_fds)
file = fdt->fd[fd];
file = rcu_dereference(fdt->fd[fd]);
return file;
}

4
include/linux/fs.h
View File

@ -9,6 +9,7 @@
#include <linux/config.h>
#include <linux/limits.h>
#include <linux/ioctl.h>
#include <linux/rcuref.h>
/*
* It's silly to have NR_OPEN bigger than NR_FILE, but you can change
@ -597,12 +598,13 @@ struct file {
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 get_file(x) rcuref_inc(&(x)->f_count)
#define file_count(x) atomic_read(&(x)->f_count)
#define MAX_NON_LFS ((1UL<<31) - 1)

5
include/linux/init_task.h
View File

@ -2,6 +2,7 @@
#define _LINUX__INIT_TASK_H
#include <linux/file.h>
#include <linux/rcupdate.h>
#define INIT_FDTABLE \
{ \
@ -11,12 +12,16 @@
.fd = &init_files.fd_array[0], \
.close_on_exec = &init_files.close_on_exec_init, \
.open_fds = &init_files.open_fds_init, \
.rcu = RCU_HEAD_INIT, \
.free_files = NULL, \
.next = NULL, \
}
#define INIT_FILES \
{ \
.count = ATOMIC_INIT(1), \
.file_lock = SPIN_LOCK_UNLOCKED, \
.fdt = &init_files.fdtab, \
.fdtab = INIT_FDTABLE, \
.close_on_exec_init = { { 0, } }, \
.open_fds_init = { { 0, } }, \

15
kernel/exit.c
View File

@ -411,15 +411,16 @@ void fastcall put_files_struct(struct files_struct *files)
close_files(files);
/*
* Free the fd and fdset arrays if we expanded them.
* If the fdtable was embedded, pass files for freeing
* at the end of the RCU grace period. Otherwise,
* you can free files immediately.
*/
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);
if (fdt == &files->fdtab)
fdt->free_files = files;
else
kmem_cache_free(files_cachep, files);
free_fdtable(fdt);
}
}

23
kernel/fork.c
View File

@ -35,6 +35,7 @@
#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>
@ -565,13 +566,12 @@ static inline int copy_fs(unsigned long clone_flags, struct task_struct * tsk)
return 0;
}
static int count_open_files(struct files_struct *files, int size)
static int count_open_files(struct fdtable *fdt)
{
int size = fdt->max_fdset;
int i;
struct fdtable *fdt;
/* Find the last open fd */
fdt = files_fdtable(files);
for (i = size/(8*sizeof(long)); i > 0; ) {
if (fdt->open_fds->fds_bits[--i])
break;
@ -592,13 +592,17 @@ static struct files_struct *alloc_files(void)
atomic_set(&newf->count, 1);
spin_lock_init(&newf->file_lock);
fdt = files_fdtable(newf);
fdt = &newf->fdtab;
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];
INIT_RCU_HEAD(&fdt->rcu);
fdt->free_files = NULL;
fdt->next = NULL;
rcu_assign_pointer(newf->fdt, fdt);
out:
return newf;
}
@ -637,7 +641,7 @@ static int copy_files(unsigned long clone_flags, struct task_struct * tsk)
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);
open_files = count_open_files(old_fdt);
expand = 0;
/*
@ -661,7 +665,14 @@ static int copy_files(unsigned long clone_flags, struct task_struct * tsk)
spin_unlock(&newf->file_lock);
if (error < 0)
goto out_release;
new_fdt = files_fdtable(newf);
/*
* Reacquire the oldf lock and a pointer to its fd table
* who knows it may have a new bigger fd table. We need
* the latest pointer.
*/
spin_lock(&oldf->file_lock);
old_fdt = files_fdtable(oldf);
}
old_fds = old_fdt->fd;
@ -683,7 +694,7 @@ static int copy_files(unsigned long clone_flags, struct task_struct * tsk)
*/
FD_CLR(open_files - i, new_fdt->open_fds);
}
*new_fds++ = f;
rcu_assign_pointer(*new_fds++, f);
}
spin_unlock(&oldf->file_lock);