[PATCH] dup_fd() fixes, part 1
Move the sucker to fs/file.c in preparation to the rest
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/file.c b/fs/file.c
index 754cd05..7dbadaa 100644
--- a/fs/file.c
+++ b/fs/file.c
@@ -261,6 +261,136 @@
return expand_fdtable(files, nr);
}
+static int count_open_files(struct fdtable *fdt)
+{
+ int size = fdt->max_fds;
+ int i;
+
+ /* Find the last open fd */
+ for (i = size/(8*sizeof(long)); i > 0; ) {
+ 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, GFP_KERNEL);
+ if (!newf)
+ goto out;
+
+ atomic_set(&newf->count, 1);
+
+ spin_lock_init(&newf->file_lock);
+ newf->next_fd = 0;
+ fdt = &newf->fdtab;
+ fdt->max_fds = NR_OPEN_DEFAULT;
+ fdt->close_on_exec = (fd_set *)&newf->close_on_exec_init;
+ fdt->open_fds = (fd_set *)&newf->open_fds_init;
+ fdt->fd = &newf->fd_array[0];
+ INIT_RCU_HEAD(&fdt->rcu);
+ fdt->next = NULL;
+ rcu_assign_pointer(newf->fdt, fdt);
+out:
+ return newf;
+}
+
+/*
+ * Allocate a new files structure and copy contents from the
+ * passed in files structure.
+ * errorp will be valid only when the returned files_struct is NULL.
+ */
+struct files_struct *dup_fd(struct files_struct *oldf, int *errorp)
+{
+ struct files_struct *newf;
+ struct file **old_fds, **new_fds;
+ int open_files, size, i;
+ struct fdtable *old_fdt, *new_fdt;
+
+ *errorp = -ENOMEM;
+ newf = alloc_files();
+ if (!newf)
+ goto out;
+
+ spin_lock(&oldf->file_lock);
+ old_fdt = files_fdtable(oldf);
+ new_fdt = files_fdtable(newf);
+ open_files = count_open_files(old_fdt);
+
+ /*
+ * Check whether we need to allocate a larger fd array and fd set.
+ * Note: we're not a clone task, so the open count won't change.
+ */
+ if (open_files > new_fdt->max_fds) {
+ new_fdt->max_fds = 0;
+ spin_unlock(&oldf->file_lock);
+ spin_lock(&newf->file_lock);
+ *errorp = expand_files(newf, open_files-1);
+ spin_unlock(&newf->file_lock);
+ if (*errorp < 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;
+ new_fds = new_fdt->fd;
+
+ 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++;
+ if (f) {
+ get_file(f);
+ } else {
+ /*
+ * The fd may be claimed in the fd bitmap but not yet
+ * instantiated in the files array if a sibling thread
+ * is partway through open(). So make sure that this
+ * fd is available to the new process.
+ */
+ FD_CLR(open_files - i, new_fdt->open_fds);
+ }
+ rcu_assign_pointer(*new_fds++, 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 / (8 * sizeof(unsigned long));
+
+ memset(&new_fdt->open_fds->fds_bits[start], 0, left);
+ memset(&new_fdt->close_on_exec->fds_bits[start], 0, left);
+ }
+
+ return newf;
+
+out_release:
+ kmem_cache_free(files_cachep, newf);
+out:
+ return NULL;
+}
+
static void __devinit fdtable_defer_list_init(int cpu)
{
struct fdtable_defer *fddef = &per_cpu(fdtable_defer_list, cpu);