diff options
| -rw-r--r-- | fs/configfs/dir.c | 106 |
1 files changed, 47 insertions, 59 deletions
diff --git a/fs/configfs/dir.c b/fs/configfs/dir.c index d4d871f..8e48b52 100644 --- a/fs/configfs/dir.c +++ b/fs/configfs/dir.c @@ -167,8 +167,8 @@ configfs_adjust_dir_dirent_depth_after_populate(struct configfs_dirent *sd) /* * Allocates a new configfs_dirent and links it to the parent configfs_dirent */ -static struct configfs_dirent *configfs_new_dirent(struct configfs_dirent * parent_sd, - void * element) +static struct configfs_dirent *configfs_new_dirent(struct configfs_dirent *parent_sd, + void *element, int type) { struct configfs_dirent * sd; @@ -180,6 +180,7 @@ static struct configfs_dirent *configfs_new_dirent(struct configfs_dirent * pare INIT_LIST_HEAD(&sd->s_links); INIT_LIST_HEAD(&sd->s_children); sd->s_element = element; + sd->s_type = type; configfs_init_dirent_depth(sd); spin_lock(&configfs_dirent_lock); if (parent_sd->s_type & CONFIGFS_USET_DROPPING) { @@ -225,12 +226,11 @@ int configfs_make_dirent(struct configfs_dirent * parent_sd, { struct configfs_dirent * sd; - sd = configfs_new_dirent(parent_sd, element); + sd = configfs_new_dirent(parent_sd, element, type); if (IS_ERR(sd)) return PTR_ERR(sd); sd->s_mode = mode; - sd->s_type = type; sd->s_dentry = dentry; if (dentry) { dentry->d_fsdata = configfs_get(sd); @@ -1006,11 +1006,11 @@ static int configfs_dump(struct configfs_dirent *sd, int level) * Note, btw, that this can be called at *any* time, even when a configfs * subsystem isn't registered, or when configfs is loading or unloading. * Just like configfs_register_subsystem(). So we take the same - * precautions. We pin the filesystem. We lock each i_mutex _in_order_ - * on our way down the tree. If we can find the target item in the + * precautions. We pin the filesystem. We lock configfs_dirent_lock. + * If we can find the target item in the * configfs tree, it must be part of the subsystem tree as well, so we - * do not need the subsystem semaphore. Holding the i_mutex chain locks - * out mkdir() and rmdir(), who might be racing us. + * do not need the subsystem semaphore. Holding configfs_dirent_lock helps + * locking out mkdir() and rmdir(), who might be racing us. */ /* @@ -1023,17 +1023,21 @@ static int configfs_dump(struct configfs_dirent *sd, int level) * do that so we can unlock it if we find nothing. * * Here we do a depth-first search of the dentry hierarchy looking for - * our object. We take i_mutex on each step of the way down. IT IS - * ESSENTIAL THAT i_mutex LOCKING IS ORDERED. If we come back up a branch, - * we'll drop the i_mutex. + * our object. + * We deliberately ignore items tagged as dropping since they are virtually + * dead, as well as items in the middle of attachment since they virtually + * do not exist yet. This completes the locking out of racing mkdir() and + * rmdir(). + * Note: subdirectories in the middle of attachment start with s_type = + * CONFIGFS_DIR|CONFIGFS_USET_CREATING set by create_dir(). When + * CONFIGFS_USET_CREATING is set, we ignore the item. The actual set of + * s_type is in configfs_new_dirent(), which has configfs_dirent_lock. * - * If the target is not found, -ENOENT is bubbled up and we have released - * all locks. If the target was found, the locks will be cleared by - * configfs_depend_rollback(). + * If the target is not found, -ENOENT is bubbled up. * * This adds a requirement that all config_items be unique! * - * This is recursive because the locking traversal is tricky. There isn't + * This is recursive. There isn't * much on the stack, though, so folks that need this function - be careful * about your stack! Patches will be accepted to make it iterative. */ @@ -1045,13 +1049,13 @@ static int configfs_depend_prep(struct dentry *origin, BUG_ON(!origin || !sd); - /* Lock this guy on the way down */ - mutex_lock(&sd->s_dentry->d_inode->i_mutex); if (sd->s_element == target) /* Boo-yah */ goto out; list_for_each_entry(child_sd, &sd->s_children, s_sibling) { - if (child_sd->s_type & CONFIGFS_DIR) { + if ((child_sd->s_type & CONFIGFS_DIR) && + !(child_sd->s_type & CONFIGFS_USET_DROPPING) && + !(child_sd->s_type & CONFIGFS_USET_CREATING)) { ret = configfs_depend_prep(child_sd->s_dentry, target); if (!ret) @@ -1060,33 +1064,12 @@ static int configfs_depend_prep(struct dentry *origin, } /* We looped all our children and didn't find target */ - mutex_unlock(&sd->s_dentry->d_inode->i_mutex); ret = -ENOENT; out: return ret; } -/* - * This is ONLY called if configfs_depend_prep() did its job. So we can - * trust the entire path from item back up to origin. - * - * We walk backwards from item, unlocking each i_mutex. We finish by - * unlocking origin. - */ -static void configfs_depend_rollback(struct dentry *origin, - struct config_item *item) -{ - struct dentry *dentry = item->ci_dentry; - - while (dentry != origin) { - mutex_unlock(&dentry->d_inode->i_mutex); - dentry = dentry->d_parent; - } - - mutex_unlock(&origin->d_inode->i_mutex); -} - int configfs_depend_item(struct configfs_subsystem *subsys, struct config_item *target) { @@ -1127,17 +1110,21 @@ int configfs_depend_item(struct configfs_subsystem *subsys, /* Ok, now we can trust subsys/s_item */ - /* Scan the tree, locking i_mutex recursively, return 0 if found */ + spin_lock(&configfs_dirent_lock); + /* Scan the tree, return 0 if found */ ret = configfs_depend_prep(subsys_sd->s_dentry, target); if (ret) - goto out_unlock_fs; + goto out_unlock_dirent_lock; - /* We hold all i_mutexes from the subsystem down to the target */ + /* + * We are sure that the item is not about to be removed by rmdir(), and + * not in the middle of attachment by mkdir(). + */ p = target->ci_dentry->d_fsdata; p->s_dependent_count += 1; - configfs_depend_rollback(subsys_sd->s_dentry, target); - +out_unlock_dirent_lock: + spin_unlock(&configfs_dirent_lock); out_unlock_fs: mutex_unlock(&configfs_sb->s_root->d_inode->i_mutex); @@ -1162,10 +1149,10 @@ void configfs_undepend_item(struct configfs_subsystem *subsys, struct configfs_dirent *sd; /* - * Since we can trust everything is pinned, we just need i_mutex - * on the item. + * Since we can trust everything is pinned, we just need + * configfs_dirent_lock. */ - mutex_lock(&target->ci_dentry->d_inode->i_mutex); + spin_lock(&configfs_dirent_lock); sd = target->ci_dentry->d_fsdata; BUG_ON(sd->s_dependent_count < 1); @@ -1176,7 +1163,7 @@ void configfs_undepend_item(struct configfs_subsystem *subsys, * After this unlock, we cannot trust the item to stay alive! * DO NOT REFERENCE item after this unlock. */ - mutex_unlock(&target->ci_dentry->d_inode->i_mutex); + spin_unlock(&configfs_dirent_lock); } EXPORT_SYMBOL(configfs_undepend_item); @@ -1376,13 +1363,6 @@ static int configfs_rmdir(struct inode *dir, struct dentry *dentry) if (sd->s_type & CONFIGFS_USET_DEFAULT) return -EPERM; - /* - * Here's where we check for dependents. We're protected by - * i_mutex. - */ - if (sd->s_dependent_count) - return -EBUSY; - /* Get a working ref until we have the child */ parent_item = configfs_get_config_item(dentry->d_parent); subsys = to_config_group(parent_item)->cg_subsys; @@ -1406,9 +1386,17 @@ static int configfs_rmdir(struct inode *dir, struct dentry *dentry) mutex_lock(&configfs_symlink_mutex); spin_lock(&configfs_dirent_lock); - ret = configfs_detach_prep(dentry, &wait_mutex); - if (ret) - configfs_detach_rollback(dentry); + /* + * Here's where we check for dependents. We're protected by + * configfs_dirent_lock. + * If no dependent, atomically tag the item as dropping. + */ + ret = sd->s_dependent_count ? -EBUSY : 0; + if (!ret) { + ret = configfs_detach_prep(dentry, &wait_mutex); + if (ret) + configfs_detach_rollback(dentry); + } spin_unlock(&configfs_dirent_lock); mutex_unlock(&configfs_symlink_mutex); @@ -1519,7 +1507,7 @@ static int configfs_dir_open(struct inode *inode, struct file *file) */ err = -ENOENT; if (configfs_dirent_is_ready(parent_sd)) { - file->private_data = configfs_new_dirent(parent_sd, NULL); + file->private_data = configfs_new_dirent(parent_sd, NULL, 0); if (IS_ERR(file->private_data)) err = PTR_ERR(file->private_data); else |
