ovl: introduce copy up waitqueue

The overlay sb 'copyup_wq' and overlay inode 'copying' condition
variable are about to replace the upper sb rename_lock, as finer
grained synchronization objects for concurrent copy up.

Suggested-by: Miklos Szeredi <miklos@szeredi.hu>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h
index 3822a90..741dc0b 100644 (file)
--- a/fs/overlayfs/overlayfs.h
+++ b/fs/overlayfs/overlayfs.h
@@ -178,6 +178,8 @@ void ovl_dentry_version_inc(struct dentry *dentry);
 u64 ovl_dentry_version_get(struct dentry *dentry);
 bool ovl_is_whiteout(struct dentry *dentry);
 struct file *ovl_path_open(struct path *path, int flags);
+int ovl_copy_up_start(struct dentry *dentry);
+void ovl_copy_up_end(struct dentry *dentry);
 
 /* namei.c */
 int ovl_path_next(int idx, struct dentry *dentry, struct path *path);

diff --git a/fs/overlayfs/ovl_entry.h b/fs/overlayfs/ovl_entry.h
index 65f2400..59614fa 100644 (file)
--- a/fs/overlayfs/ovl_entry.h
+++ b/fs/overlayfs/ovl_entry.h
@@ -28,6 +28,7 @@ struct ovl_fs {
        /* creds of process who forced instantiation of super block */
        const struct cred *creator_cred;
        bool tmpfile;
+       wait_queue_head_t copyup_wq;
 };
 
 /* private information held for every overlayfs dentry */
@@ -39,6 +40,7 @@ struct ovl_entry {
                        u64 version;
                        const char *redirect;
                        bool opaque;
+                       bool copying;
                };
                struct rcu_head rcu;
        };

diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index ff05065..6792bb7 100644 (file)
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -708,6 +708,7 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
        if (!ufs)
                goto out;
 
+       init_waitqueue_head(&ufs->copyup_wq);
        ufs->config.redirect_dir = ovl_redirect_dir_def;
        err = ovl_parse_opt((char *) data, &ufs->config);
        if (err)

diff --git a/fs/overlayfs/util.c b/fs/overlayfs/util.c
index 952286f..01157d6 100644 (file)
--- a/fs/overlayfs/util.c
+++ b/fs/overlayfs/util.c
@@ -263,3 +263,33 @@ struct file *ovl_path_open(struct path *path, int flags)
 {
        return dentry_open(path, flags | O_NOATIME, current_cred());
 }
+
+int ovl_copy_up_start(struct dentry *dentry)
+{
+       struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
+       struct ovl_entry *oe = dentry->d_fsdata;
+       int err;
+
+       spin_lock(&ofs->copyup_wq.lock);
+       err = wait_event_interruptible_locked(ofs->copyup_wq, !oe->copying);
+       if (!err) {
+               if (oe->__upperdentry)
+                       err = 1; /* Already copied up */
+               else
+                       oe->copying = true;
+       }
+       spin_unlock(&ofs->copyup_wq.lock);
+
+       return err;
+}
+
+void ovl_copy_up_end(struct dentry *dentry)
+{
+       struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
+       struct ovl_entry *oe = dentry->d_fsdata;
+
+       spin_lock(&ofs->copyup_wq.lock);
+       oe->copying = false;
+       wake_up_locked(&ofs->copyup_wq);
+       spin_unlock(&ofs->copyup_wq.lock);
+}