From b0841eefd9693827afb9888235e26ddd098f9cef Mon Sep 17 00:00:00 2001 From: Al Viro Date: Sat, 31 Aug 2019 09:43:43 +0200 Subject: configfs: provide exclusion between IO and removals Make sure that attribute methods are not called after the item has been removed from the tree. To do so, we * at the point of no return in removals, grab ->frag_sem exclusive and mark the fragment dead. * call the methods of attributes with ->frag_sem taken shared and only after having verified that the fragment is still alive. The main benefit is for method instances - they are guaranteed that the objects they are accessing *and* all ancestors are still there. Another win is that we don't need to bother with extra refcount on config_item when opening a file - the item will be alive for as long as it stays in the tree, and we won't touch it/attributes/any associated data after it's been removed from the tree. Signed-off-by: Al Viro Signed-off-by: Christoph Hellwig --- fs/configfs/dir.c | 23 +++++++++++++++++++++++ 1 file changed, 23 insertions(+) (limited to 'fs/configfs/dir.c') diff --git a/fs/configfs/dir.c b/fs/configfs/dir.c index 1df65c2440da..79fc25aaa8cd 100644 --- a/fs/configfs/dir.c +++ b/fs/configfs/dir.c @@ -1461,6 +1461,7 @@ static int configfs_rmdir(struct inode *dir, struct dentry *dentry) struct config_item *item; struct configfs_subsystem *subsys; struct configfs_dirent *sd; + struct configfs_fragment *frag; struct module *subsys_owner = NULL, *dead_item_owner = NULL; int ret; @@ -1518,6 +1519,16 @@ static int configfs_rmdir(struct inode *dir, struct dentry *dentry) } } while (ret == -EAGAIN); + frag = sd->s_frag; + if (down_write_killable(&frag->frag_sem)) { + spin_lock(&configfs_dirent_lock); + configfs_detach_rollback(dentry); + spin_unlock(&configfs_dirent_lock); + return -EINTR; + } + frag->frag_dead = true; + up_write(&frag->frag_sem); + /* Get a working ref for the duration of this function */ item = configfs_get_config_item(dentry); @@ -1821,6 +1832,12 @@ void configfs_unregister_group(struct config_group *group) struct configfs_subsystem *subsys = group->cg_subsys; struct dentry *dentry = group->cg_item.ci_dentry; struct dentry *parent = group->cg_item.ci_parent->ci_dentry; + struct configfs_dirent *sd = dentry->d_fsdata; + struct configfs_fragment *frag = sd->s_frag; + + down_write(&frag->frag_sem); + frag->frag_dead = true; + up_write(&frag->frag_sem); inode_lock_nested(d_inode(parent), I_MUTEX_PARENT); spin_lock(&configfs_dirent_lock); @@ -1947,12 +1964,18 @@ void configfs_unregister_subsystem(struct configfs_subsystem *subsys) struct config_group *group = &subsys->su_group; struct dentry *dentry = group->cg_item.ci_dentry; struct dentry *root = dentry->d_sb->s_root; + struct configfs_dirent *sd = dentry->d_fsdata; + struct configfs_fragment *frag = sd->s_frag; if (dentry->d_parent != root) { pr_err("Tried to unregister non-subsystem!\n"); return; } + down_write(&frag->frag_sem); + frag->frag_dead = true; + up_write(&frag->frag_sem); + inode_lock_nested(d_inode(root), I_MUTEX_PARENT); inode_lock_nested(d_inode(dentry), I_MUTEX_CHILD); -- cgit v1.2.3