diff options
Diffstat (limited to 'fs/configfs')
| -rw-r--r-- | fs/configfs/configfs_internal.h | 7 | ||||
| -rw-r--r-- | fs/configfs/dir.c | 244 |
2 files changed, 248 insertions, 3 deletions
diff --git a/fs/configfs/configfs_internal.h b/fs/configfs/configfs_internal.h index 7b48c034b31..3b0185fdf9a 100644 --- a/fs/configfs/configfs_internal.h +++ b/fs/configfs/configfs_internal.h @@ -29,10 +29,11 @@ struct configfs_dirent { atomic_t s_count; + int s_dependent_count; struct list_head s_sibling; struct list_head s_children; struct list_head s_links; - void * s_element; + void * s_element; int s_type; umode_t s_mode; struct dentry * s_dentry; @@ -41,8 +42,8 @@ struct configfs_dirent { #define CONFIGFS_ROOT 0x0001 #define CONFIGFS_DIR 0x0002 -#define CONFIGFS_ITEM_ATTR 0x0004 -#define CONFIGFS_ITEM_LINK 0x0020 +#define CONFIGFS_ITEM_ATTR 0x0004 +#define CONFIGFS_ITEM_LINK 0x0020 #define CONFIGFS_USET_DIR 0x0040 #define CONFIGFS_USET_DEFAULT 0x0080 #define CONFIGFS_USET_DROPPING 0x0100 diff --git a/fs/configfs/dir.c b/fs/configfs/dir.c index 125954723eb..2f436d4f1d6 100644 --- a/fs/configfs/dir.c +++ b/fs/configfs/dir.c @@ -355,6 +355,10 @@ static int configfs_detach_prep(struct dentry *dentry) /* Mark that we've taken i_mutex */ sd->s_type |= CONFIGFS_USET_DROPPING; + /* + * Yup, recursive. If there's a problem, blame + * deep nesting of default_groups + */ ret = configfs_detach_prep(sd->s_dentry); if (!ret) continue; @@ -760,6 +764,239 @@ static void client_drop_item(struct config_item *parent_item, config_item_put(item); } +#ifdef DEBUG +static void configfs_dump_one(struct configfs_dirent *sd, int level) +{ + printk(KERN_INFO "%*s\"%s\":\n", level, " ", configfs_get_name(sd)); + +#define type_print(_type) if (sd->s_type & _type) printk(KERN_INFO "%*s %s\n", level, " ", #_type); + type_print(CONFIGFS_ROOT); + type_print(CONFIGFS_DIR); + type_print(CONFIGFS_ITEM_ATTR); + type_print(CONFIGFS_ITEM_LINK); + type_print(CONFIGFS_USET_DIR); + type_print(CONFIGFS_USET_DEFAULT); + type_print(CONFIGFS_USET_DROPPING); +#undef type_print +} + +static int configfs_dump(struct configfs_dirent *sd, int level) +{ + struct configfs_dirent *child_sd; + int ret = 0; + + configfs_dump_one(sd, level); + + if (!(sd->s_type & (CONFIGFS_DIR|CONFIGFS_ROOT))) + return 0; + + list_for_each_entry(child_sd, &sd->s_children, s_sibling) { + ret = configfs_dump(child_sd, level + 2); + if (ret) + break; + } + + return ret; +} +#endif + + +/* + * configfs_depend_item() and configfs_undepend_item() + * + * WARNING: Do not call these from a configfs callback! + * + * This describes these functions and their helpers. + * + * Allow another kernel system to depend on a config_item. If this + * happens, the item cannot go away until the dependant can live without + * it. The idea is to give client modules as simple an interface as + * possible. When a system asks them to depend on an item, they just + * call configfs_depend_item(). If the item is live and the client + * driver is in good shape, we'll happily do the work for them. + * + * Why is the locking complex? Because configfs uses the VFS to handle + * all locking, but this function is called outside the normal + * VFS->configfs path. So it must take VFS locks to prevent the + * VFS->configfs stuff (configfs_mkdir(), configfs_rmdir(), etc). This is + * why you can't call these functions underneath configfs callbacks. + * + * 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 + * 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. + */ + +/* + * configfs_depend_prep() + * + * Only subdirectories count here. Files (CONFIGFS_NOT_PINNED) are + * attributes. This is similar but not the same to configfs_detach_prep(). + * Note that configfs_detach_prep() expects the parent to be locked when it + * is called, but we lock the parent *inside* configfs_depend_prep(). We + * 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. + * + * 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(). + * + * This adds a requirement that all config_items be unique! + * + * This is recursive because the locking traversal is tricky. 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. + */ +static int configfs_depend_prep(struct dentry *origin, + struct config_item *target) +{ + struct configfs_dirent *child_sd, *sd = origin->d_fsdata; + int ret = 0; + + 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) { + ret = configfs_depend_prep(child_sd->s_dentry, + target); + if (!ret) + goto out; /* Child path boo-yah */ + } + } + + /* 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) +{ + int ret; + struct configfs_dirent *p, *root_sd, *subsys_sd = NULL; + struct config_item *s_item = &subsys->su_group.cg_item; + + /* + * Pin the configfs filesystem. This means we can safely access + * the root of the configfs filesystem. + */ + ret = configfs_pin_fs(); + if (ret) + return ret; + + /* + * Next, lock the root directory. We're going to check that the + * subsystem is really registered, and so we need to lock out + * configfs_[un]register_subsystem(). + */ + mutex_lock(&configfs_sb->s_root->d_inode->i_mutex); + + root_sd = configfs_sb->s_root->d_fsdata; + + list_for_each_entry(p, &root_sd->s_children, s_sibling) { + if (p->s_type & CONFIGFS_DIR) { + if (p->s_element == s_item) { + subsys_sd = p; + break; + } + } + } + + if (!subsys_sd) { + ret = -ENOENT; + goto out_unlock_fs; + } + + /* Ok, now we can trust subsys/s_item */ + + /* Scan the tree, locking i_mutex recursively, return 0 if found */ + ret = configfs_depend_prep(subsys_sd->s_dentry, target); + if (ret) + goto out_unlock_fs; + + /* We hold all i_mutexes from the subsystem down to the target */ + p = target->ci_dentry->d_fsdata; + p->s_dependent_count += 1; + + configfs_depend_rollback(subsys_sd->s_dentry, target); + +out_unlock_fs: + mutex_unlock(&configfs_sb->s_root->d_inode->i_mutex); + + /* + * If we succeeded, the fs is pinned via other methods. If not, + * we're done with it anyway. So release_fs() is always right. + */ + configfs_release_fs(); + + return ret; +} +EXPORT_SYMBOL(configfs_depend_item); + +/* + * Release the dependent linkage. This is much simpler than + * configfs_depend_item() because we know that that the client driver is + * pinned, thus the subsystem is pinned, and therefore configfs is pinned. + */ +void configfs_undepend_item(struct configfs_subsystem *subsys, + struct config_item *target) +{ + struct configfs_dirent *sd; + + /* + * Since we can trust everything is pinned, we just need i_mutex + * on the item. + */ + mutex_lock(&target->ci_dentry->d_inode->i_mutex); + + sd = target->ci_dentry->d_fsdata; + BUG_ON(sd->s_dependent_count < 1); + + sd->s_dependent_count -= 1; + + /* + * 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); +} +EXPORT_SYMBOL(configfs_undepend_item); static int configfs_mkdir(struct inode *dir, struct dentry *dentry, int mode) { @@ -906,6 +1143,13 @@ 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; |