Add the rt linux 4.1.3-rt3 as base

[kvmfornfv.git] / kernel / fs / fs_struct.c

diff --git a/kernel/fs/fs_struct.c b/kernel/fs/fs_struct.c
new file mode 100644 (file)
index 0000000..7dca743
--- /dev/null
+++ b/kernel/fs/fs_struct.c
@@ -0,0 +1,166 @@
+#include <linux/export.h>
+#include <linux/sched.h>
+#include <linux/fs.h>
+#include <linux/path.h>
+#include <linux/slab.h>
+#include <linux/fs_struct.h>
+#include "internal.h"
+
+/*
+ * Replace the fs->{rootmnt,root} with {mnt,dentry}. Put the old values.
+ * It can block.
+ */
+void set_fs_root(struct fs_struct *fs, const struct path *path)
+{
+       struct path old_root;
+
+       path_get(path);
+       spin_lock(&fs->lock);
+       write_seqcount_begin(&fs->seq);
+       old_root = fs->root;
+       fs->root = *path;
+       write_seqcount_end(&fs->seq);
+       spin_unlock(&fs->lock);
+       if (old_root.dentry)
+               path_put(&old_root);
+}
+
+/*
+ * Replace the fs->{pwdmnt,pwd} with {mnt,dentry}. Put the old values.
+ * It can block.
+ */
+void set_fs_pwd(struct fs_struct *fs, const struct path *path)
+{
+       struct path old_pwd;
+
+       path_get(path);
+       spin_lock(&fs->lock);
+       write_seqcount_begin(&fs->seq);
+       old_pwd = fs->pwd;
+       fs->pwd = *path;
+       write_seqcount_end(&fs->seq);
+       spin_unlock(&fs->lock);
+
+       if (old_pwd.dentry)
+               path_put(&old_pwd);
+}
+
+static inline int replace_path(struct path *p, const struct path *old, const struct path *new)
+{
+       if (likely(p->dentry != old->dentry || p->mnt != old->mnt))
+               return 0;
+       *p = *new;
+       return 1;
+}
+
+void chroot_fs_refs(const struct path *old_root, const struct path *new_root)
+{
+       struct task_struct *g, *p;
+       struct fs_struct *fs;
+       int count = 0;
+
+       read_lock(&tasklist_lock);
+       do_each_thread(g, p) {
+               task_lock(p);
+               fs = p->fs;
+               if (fs) {
+                       int hits = 0;
+                       spin_lock(&fs->lock);
+                       write_seqcount_begin(&fs->seq);
+                       hits += replace_path(&fs->root, old_root, new_root);
+                       hits += replace_path(&fs->pwd, old_root, new_root);
+                       write_seqcount_end(&fs->seq);
+                       while (hits--) {
+                               count++;
+                               path_get(new_root);
+                       }
+                       spin_unlock(&fs->lock);
+               }
+               task_unlock(p);
+       } while_each_thread(g, p);
+       read_unlock(&tasklist_lock);
+       while (count--)
+               path_put(old_root);
+}
+
+void free_fs_struct(struct fs_struct *fs)
+{
+       path_put(&fs->root);
+       path_put(&fs->pwd);
+       kmem_cache_free(fs_cachep, fs);
+}
+
+void exit_fs(struct task_struct *tsk)
+{
+       struct fs_struct *fs = tsk->fs;
+
+       if (fs) {
+               int kill;
+               task_lock(tsk);
+               spin_lock(&fs->lock);
+               tsk->fs = NULL;
+               kill = !--fs->users;
+               spin_unlock(&fs->lock);
+               task_unlock(tsk);
+               if (kill)
+                       free_fs_struct(fs);
+       }
+}
+
+struct fs_struct *copy_fs_struct(struct fs_struct *old)
+{
+       struct fs_struct *fs = kmem_cache_alloc(fs_cachep, GFP_KERNEL);
+       /* We don't need to lock fs - think why ;-) */
+       if (fs) {
+               fs->users = 1;
+               fs->in_exec = 0;
+               spin_lock_init(&fs->lock);
+               seqcount_init(&fs->seq);
+               fs->umask = old->umask;
+
+               spin_lock(&old->lock);
+               fs->root = old->root;
+               path_get(&fs->root);
+               fs->pwd = old->pwd;
+               path_get(&fs->pwd);
+               spin_unlock(&old->lock);
+       }
+       return fs;
+}
+
+int unshare_fs_struct(void)
+{
+       struct fs_struct *fs = current->fs;
+       struct fs_struct *new_fs = copy_fs_struct(fs);
+       int kill;
+
+       if (!new_fs)
+               return -ENOMEM;
+
+       task_lock(current);
+       spin_lock(&fs->lock);
+       kill = !--fs->users;
+       current->fs = new_fs;
+       spin_unlock(&fs->lock);
+       task_unlock(current);
+
+       if (kill)
+               free_fs_struct(fs);
+
+       return 0;
+}
+EXPORT_SYMBOL_GPL(unshare_fs_struct);
+
+int current_umask(void)
+{
+       return current->fs->umask;
+}
+EXPORT_SYMBOL(current_umask);
+
+/* to be mentioned only in INIT_TASK */
+struct fs_struct init_fs = {
+       .users          = 1,
+       .lock           = __SPIN_LOCK_UNLOCKED(init_fs.lock),
+       .seq            = SEQCNT_ZERO(init_fs.seq),
+       .umask          = 0022,
+};