__free_fdtable(container_of(rcu, struct fdtable, rcu));
}
+#define BITBIT_NR(nr) BITS_TO_LONGS(BITS_TO_LONGS(nr))
+#define BITBIT_SIZE(nr) (BITBIT_NR(nr) * sizeof(long))
+
+/*
+ * Copy 'count' fd bits from the old table to the new table and clear the extra
+ * space if any. This does not copy the file pointers. Called with the files
+ * spinlock held for write.
+ */
+static void copy_fd_bitmaps(struct fdtable *nfdt, struct fdtable *ofdt,
+ unsigned int count)
+{
+ unsigned int cpy, set;
+
+ cpy = count / BITS_PER_BYTE;
+ set = (nfdt->max_fds - count) / BITS_PER_BYTE;
+ memcpy(nfdt->open_fds, ofdt->open_fds, cpy);
+ memset((char *)nfdt->open_fds + cpy, 0, set);
+ memcpy(nfdt->close_on_exec, ofdt->close_on_exec, cpy);
+ memset((char *)nfdt->close_on_exec + cpy, 0, set);
+
+ cpy = BITBIT_SIZE(count);
+ set = BITBIT_SIZE(nfdt->max_fds) - cpy;
+ memcpy(nfdt->full_fds_bits, ofdt->full_fds_bits, cpy);
+ memset((char *)nfdt->full_fds_bits + cpy, 0, set);
+}
+
/*
- * Expand the fdset in the files_struct. Called with the files spinlock
- * held for write.
+ * Copy all file descriptors from the old table to the new, expanded table and
+ * clear the extra space. Called with the files spinlock held for write.
*/
static void copy_fdtable(struct fdtable *nfdt, struct fdtable *ofdt)
{
cpy = ofdt->max_fds * sizeof(struct file *);
set = (nfdt->max_fds - ofdt->max_fds) * sizeof(struct file *);
memcpy(nfdt->fd, ofdt->fd, cpy);
- memset((char *)(nfdt->fd) + cpy, 0, set);
+ memset((char *)nfdt->fd + cpy, 0, set);
- cpy = ofdt->max_fds / BITS_PER_BYTE;
- set = (nfdt->max_fds - ofdt->max_fds) / BITS_PER_BYTE;
- memcpy(nfdt->open_fds, ofdt->open_fds, cpy);
- memset((char *)(nfdt->open_fds) + cpy, 0, set);
- memcpy(nfdt->close_on_exec, ofdt->close_on_exec, cpy);
- memset((char *)(nfdt->close_on_exec) + cpy, 0, set);
+ copy_fd_bitmaps(nfdt, ofdt, ofdt->max_fds);
}
static struct fdtable * alloc_fdtable(unsigned int nr)
fdt->fd = data;
data = alloc_fdmem(max_t(size_t,
- 2 * nr / BITS_PER_BYTE, L1_CACHE_BYTES));
+ 2 * nr / BITS_PER_BYTE + BITBIT_SIZE(nr), L1_CACHE_BYTES));
if (!data)
goto out_arr;
fdt->open_fds = data;
data += nr / BITS_PER_BYTE;
fdt->close_on_exec = data;
+ data += nr / BITS_PER_BYTE;
+ fdt->full_fds_bits = data;
return fdt;
spin_unlock(&files->file_lock);
new_fdt = alloc_fdtable(nr);
+
+ /* make sure all __fd_install() have seen resize_in_progress
+ * or have finished their rcu_read_lock_sched() section.
+ */
+ if (atomic_read(&files->count) > 1)
+ synchronize_sched();
+
spin_lock(&files->file_lock);
if (!new_fdt)
return -ENOMEM;
__free_fdtable(new_fdt);
return -EMFILE;
}
- /*
- * Check again since another task may have expanded the fd table while
- * we dropped the lock
- */
cur_fdt = files_fdtable(files);
- if (nr >= cur_fdt->max_fds) {
- /* Continue as planned */
- copy_fdtable(new_fdt, cur_fdt);
- rcu_assign_pointer(files->fdt, new_fdt);
- if (cur_fdt != &files->fdtab)
- call_rcu(&cur_fdt->rcu, free_fdtable_rcu);
- } else {
- /* Somebody else expanded, so undo our attempt */
- __free_fdtable(new_fdt);
- }
+ BUG_ON(nr < cur_fdt->max_fds);
+ copy_fdtable(new_fdt, cur_fdt);
+ rcu_assign_pointer(files->fdt, new_fdt);
+ if (cur_fdt != &files->fdtab)
+ call_rcu(&cur_fdt->rcu, free_fdtable_rcu);
+ /* coupled with smp_rmb() in __fd_install() */
+ smp_wmb();
return 1;
}
* The files->file_lock should be held on entry, and will be held on exit.
*/
static int expand_files(struct files_struct *files, int nr)
+ __releases(files->file_lock)
+ __acquires(files->file_lock)
{
struct fdtable *fdt;
+ int expanded = 0;
+repeat:
fdt = files_fdtable(files);
/* Do we need to expand? */
if (nr < fdt->max_fds)
- return 0;
+ return expanded;
/* Can we expand? */
if (nr >= sysctl_nr_open)
return -EMFILE;
+ if (unlikely(files->resize_in_progress)) {
+ spin_unlock(&files->file_lock);
+ expanded = 1;
+ wait_event(files->resize_wait, !files->resize_in_progress);
+ spin_lock(&files->file_lock);
+ goto repeat;
+ }
+
/* All good, so we try */
- return expand_fdtable(files, nr);
+ files->resize_in_progress = true;
+ expanded = expand_fdtable(files, nr);
+ files->resize_in_progress = false;
+
+ wake_up_all(&files->resize_wait);
+ return expanded;
}
static inline void __set_close_on_exec(int fd, struct fdtable *fdt)
static inline void __clear_close_on_exec(int fd, struct fdtable *fdt)
{
- __clear_bit(fd, fdt->close_on_exec);
+ if (test_bit(fd, fdt->close_on_exec))
+ __clear_bit(fd, fdt->close_on_exec);
}
-static inline void __set_open_fd(int fd, struct fdtable *fdt)
+static inline void __set_open_fd(unsigned int fd, struct fdtable *fdt)
{
__set_bit(fd, fdt->open_fds);
+ fd /= BITS_PER_LONG;
+ if (!~fdt->open_fds[fd])
+ __set_bit(fd, fdt->full_fds_bits);
}
-static inline void __clear_open_fd(int fd, struct fdtable *fdt)
+static inline void __clear_open_fd(unsigned int fd, struct fdtable *fdt)
{
__clear_bit(fd, fdt->open_fds);
+ __clear_bit(fd / BITS_PER_LONG, fdt->full_fds_bits);
}
static int count_open_files(struct fdtable *fdt)
{
struct files_struct *newf;
struct file **old_fds, **new_fds;
- int open_files, size, i;
+ int open_files, i;
struct fdtable *old_fdt, *new_fdt;
*errorp = -ENOMEM;
atomic_set(&newf->count, 1);
spin_lock_init(&newf->file_lock);
+ newf->resize_in_progress = false;
+ init_waitqueue_head(&newf->resize_wait);
newf->next_fd = 0;
new_fdt = &newf->fdtab;
new_fdt->max_fds = NR_OPEN_DEFAULT;
new_fdt->close_on_exec = newf->close_on_exec_init;
new_fdt->open_fds = newf->open_fds_init;
+ new_fdt->full_fds_bits = newf->full_fds_bits_init;
new_fdt->fd = &newf->fd_array[0];
spin_lock(&oldf->file_lock);
open_files = count_open_files(old_fdt);
}
+ copy_fd_bitmaps(new_fdt, old_fdt, open_files);
+
old_fds = old_fdt->fd;
new_fds = new_fdt->fd;
- memcpy(new_fdt->open_fds, old_fdt->open_fds, open_files / 8);
- memcpy(new_fdt->close_on_exec, old_fdt->close_on_exec, open_files / 8);
-
for (i = open_files; i != 0; i--) {
struct file *f = *old_fds++;
if (f) {
}
spin_unlock(&oldf->file_lock);
- /* compute the remainder to be cleared */
- 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 (new_fdt->max_fds > open_files) {
- int left = (new_fdt->max_fds - open_files) / 8;
- int start = open_files / BITS_PER_LONG;
-
- memset(&new_fdt->open_fds[start], 0, left);
- memset(&new_fdt->close_on_exec[start], 0, left);
- }
+ /* clear the remainder */
+ memset(new_fds, 0, (new_fdt->max_fds - open_files) * sizeof(struct file *));
rcu_assign_pointer(newf->fdt, new_fdt);
.fd = &init_files.fd_array[0],
.close_on_exec = init_files.close_on_exec_init,
.open_fds = init_files.open_fds_init,
+ .full_fds_bits = init_files.full_fds_bits_init,
},
.file_lock = __SPIN_LOCK_UNLOCKED(init_files.file_lock),
};
+static unsigned long find_next_fd(struct fdtable *fdt, unsigned long start)
+{
+ unsigned long maxfd = fdt->max_fds;
+ unsigned long maxbit = maxfd / BITS_PER_LONG;
+ unsigned long bitbit = start / BITS_PER_LONG;
+
+ bitbit = find_next_zero_bit(fdt->full_fds_bits, maxbit, bitbit) * BITS_PER_LONG;
+ if (bitbit > maxfd)
+ return maxfd;
+ if (bitbit > start)
+ start = bitbit;
+ return find_next_zero_bit(fdt->open_fds, maxfd, start);
+}
+
/*
* allocate a file descriptor, mark it busy.
*/
fd = files->next_fd;
if (fd < fdt->max_fds)
- fd = find_next_zero_bit(fdt->open_fds, fdt->max_fds, fd);
+ fd = find_next_fd(fdt, fd);
/*
* N.B. For clone tasks sharing a files structure, this test
struct file *file)
{
struct fdtable *fdt;
- spin_lock(&files->file_lock);
- fdt = files_fdtable(files);
+
+ might_sleep();
+ rcu_read_lock_sched();
+
+ while (unlikely(files->resize_in_progress)) {
+ rcu_read_unlock_sched();
+ wait_event(files->resize_wait, !files->resize_in_progress);
+ rcu_read_lock_sched();
+ }
+ /* coupled with smp_wmb() in expand_fdtable() */
+ smp_rmb();
+ fdt = rcu_dereference_sched(files->fdt);
BUG_ON(fdt->fd[fd] != NULL);
rcu_assign_pointer(fdt->fd[fd], file);
- spin_unlock(&files->file_lock);
+ rcu_read_unlock_sched();
}
void fd_install(unsigned int fd, struct file *file)
struct file *file;
rcu_read_lock();
+loop:
file = fcheck_files(files, fd);
if (file) {
- /* File object ref couldn't be taken */
- if ((file->f_mode & mask) || !get_file_rcu(file))
+ /* File object ref couldn't be taken.
+ * dup2() atomicity guarantee is the reason
+ * we loop to catch the new file (or NULL pointer)
+ */
+ if (file->f_mode & mask)
file = NULL;
+ else if (!get_file_rcu(file))
+ goto loop;
}
rcu_read_unlock();
Code Review / kvmfornfv.git / blobdiff