1 files changed, 150 insertions, 2 deletions

diff --git a/fs/file.c b/fs/file.c
index 4c6f0ea12c41..7b3887e054d0 100644
--- a/fs/file.c
+++ b/fs/file.c
@@ -26,6 +26,8 @@ struct fdtable_defer {
 };
 
 int sysctl_nr_open __read_mostly = 1024*1024;
+int sysctl_nr_open_min = BITS_PER_LONG;
+int sysctl_nr_open_max = 1024 * 1024; /* raised later */
 
 /*
  * We use this list to defer free fdtables that have vmalloced
@@ -119,8 +121,6 @@ static void copy_fdtable(struct fdtable *nfdt, struct fdtable *ofdt)
         unsigned int cpy, set;
 
         BUG_ON(nfdt->max_fds < ofdt->max_fds);
-        if (ofdt->max_fds == 0)
-                return;
 
         cpy = ofdt->max_fds * sizeof(struct file *);
         set = (nfdt->max_fds - ofdt->max_fds) * sizeof(struct file *);
@@ -261,6 +261,139 @@ int expand_files(struct files_struct *files, int nr)
         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;
+}
+
+/*
+ * 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 = 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;
+        new_fdt = &newf->fdtab;
+        new_fdt->max_fds = NR_OPEN_DEFAULT;
+        new_fdt->close_on_exec = (fd_set *)&newf->close_on_exec_init;
+        new_fdt->open_fds = (fd_set *)&newf->open_fds_init;
+        new_fdt->fd = &newf->fd_array[0];
+        INIT_RCU_HEAD(&new_fdt->rcu);
+        new_fdt->next = NULL;
+
+        spin_lock(&oldf->file_lock);
+        old_fdt = files_fdtable(oldf);
+        open_files = count_open_files(old_fdt);
+
+        /*
+         * Check whether we need to allocate a larger fd array and fd set.
+         */
+        while (unlikely(open_files > new_fdt->max_fds)) {
+                spin_unlock(&oldf->file_lock);
+
+                if (new_fdt != &newf->fdtab) {
+                        free_fdarr(new_fdt);
+                        free_fdset(new_fdt);
+                        kfree(new_fdt);
+                }
+
+                new_fdt = alloc_fdtable(open_files - 1);
+                if (!new_fdt) {
+                        *errorp = -ENOMEM;
+                        goto out_release;
+                }
+
+                /* beyond sysctl_nr_open; nothing to do */
+                if (unlikely(new_fdt->max_fds < open_files)) {
+                        free_fdarr(new_fdt);
+                        free_fdset(new_fdt);
+                        kfree(new_fdt);
+                        *errorp = -EMFILE;
+                        goto out_release;
+                }
+
+                /*
+                 * 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);
+                open_files = count_open_files(old_fdt);
+        }
+
+        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);
+        }
+
+        rcu_assign_pointer(newf->fdt, new_fdt);
+
+        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);
@@ -274,4 +407,19 @@ void __init files_defer_init(void)
         int i;
         for_each_possible_cpu(i)
                 fdtable_defer_list_init(i);
+        sysctl_nr_open_max = min((size_t)INT_MAX, ~(size_t)0/sizeof(void *)) &
+                             -BITS_PER_LONG;
 }
+
+struct files_struct init_files = {
+        .count          = ATOMIC_INIT(1),
+        .fdt            = &init_files.fdtab,
+        .fdtab          = {
+                .max_fds        = NR_OPEN_DEFAULT,
+                .fd             = &init_files.fd_array[0],
+                .close_on_exec  = (fd_set *)&init_files.close_on_exec_init,
+                .open_fds       = (fd_set *)&init_files.open_fds_init,
+                .rcu            = RCU_HEAD_INIT,
+        },
+        .file_lock      = __SPIN_LOCK_UNLOCKED(init_task.file_lock),
+};