X-Git-Url: http://pilppa.org/gitweb/gitweb.cgi?a=blobdiff_plain;f=fs%2Fconfigfs%2Fdir.c;h=2495f23e33f45b767a88e825f6606126c073814d;hb=dacdd0e04768da1fd2b24a6ee274c582b40d0c5b;hp=a48dc7dd8765399936cd8c1fbd7fe80d7949e68c;hpb=ef3f2de2b5496f721b12f21a157e19eac816394b;p=linux-2.6-omap-h63xx.git diff --git a/fs/configfs/dir.c b/fs/configfs/dir.c index a48dc7dd876..2495f23e33f 100644 --- a/fs/configfs/dir.c +++ b/fs/configfs/dir.c @@ -30,11 +30,25 @@ #include #include #include +#include #include #include "configfs_internal.h" DECLARE_RWSEM(configfs_rename_sem); +/* + * Protects mutations of configfs_dirent linkage together with proper i_mutex + * Also protects mutations of symlinks linkage to target configfs_dirent + * Mutators of configfs_dirent linkage must *both* have the proper inode locked + * and configfs_dirent_lock locked, in that order. + * This allows one to safely traverse configfs_dirent trees and symlinks without + * having to lock inodes. + * + * Protects setting of CONFIGFS_USET_DROPPING: checking the flag + * unlocked is not reliable unless in detach_groups() called from + * rmdir()/unregister() and from configfs_attach_group() + */ +DEFINE_SPINLOCK(configfs_dirent_lock); static void configfs_d_iput(struct dentry * dentry, struct inode * inode) @@ -74,13 +88,20 @@ static struct configfs_dirent *configfs_new_dirent(struct configfs_dirent * pare sd = kmem_cache_zalloc(configfs_dir_cachep, GFP_KERNEL); if (!sd) - return NULL; + return ERR_PTR(-ENOMEM); atomic_set(&sd->s_count, 1); INIT_LIST_HEAD(&sd->s_links); INIT_LIST_HEAD(&sd->s_children); - list_add(&sd->s_sibling, &parent_sd->s_children); sd->s_element = element; + spin_lock(&configfs_dirent_lock); + if (parent_sd->s_type & CONFIGFS_USET_DROPPING) { + spin_unlock(&configfs_dirent_lock); + kmem_cache_free(configfs_dir_cachep, sd); + return ERR_PTR(-ENOENT); + } + list_add(&sd->s_sibling, &parent_sd->s_children); + spin_unlock(&configfs_dirent_lock); return sd; } @@ -118,8 +139,8 @@ int configfs_make_dirent(struct configfs_dirent * parent_sd, struct configfs_dirent * sd; sd = configfs_new_dirent(parent_sd, element); - if (!sd) - return -ENOMEM; + if (IS_ERR(sd)) + return PTR_ERR(sd); sd->s_mode = mode; sd->s_type = type; @@ -173,7 +194,9 @@ static int create_dir(struct config_item * k, struct dentry * p, } else { struct configfs_dirent *sd = d->d_fsdata; if (sd) { + spin_lock(&configfs_dirent_lock); list_del_init(&sd->s_sibling); + spin_unlock(&configfs_dirent_lock); configfs_put(sd); } } @@ -224,7 +247,9 @@ int configfs_create_link(struct configfs_symlink *sl, else { struct configfs_dirent *sd = dentry->d_fsdata; if (sd) { + spin_lock(&configfs_dirent_lock); list_del_init(&sd->s_sibling); + spin_unlock(&configfs_dirent_lock); configfs_put(sd); } } @@ -238,7 +263,9 @@ static void remove_dir(struct dentry * d) struct configfs_dirent * sd; sd = d->d_fsdata; + spin_lock(&configfs_dirent_lock); list_del_init(&sd->s_sibling); + spin_unlock(&configfs_dirent_lock); configfs_put(sd); if (d->d_inode) simple_rmdir(parent->d_inode,d); @@ -331,13 +358,13 @@ static struct dentry * configfs_lookup(struct inode *dir, /* * Only subdirectories count here. Files (CONFIGFS_NOT_PINNED) are - * attributes and are removed by rmdir(). We recurse, taking i_mutex - * on all children that are candidates for default detach. If the - * result is clean, then configfs_detach_group() will handle dropping - * i_mutex. If there is an error, the caller will clean up the i_mutex - * holders via configfs_detach_rollback(). + * attributes and are removed by rmdir(). We recurse, setting + * CONFIGFS_USET_DROPPING on all children that are candidates for + * default detach. + * If there is an error, the caller will reset the flags via + * configfs_detach_rollback(). */ -static int configfs_detach_prep(struct dentry *dentry) +static int configfs_detach_prep(struct dentry *dentry, struct mutex **wait_mutex) { struct configfs_dirent *parent_sd = dentry->d_fsdata; struct configfs_dirent *sd; @@ -352,15 +379,20 @@ static int configfs_detach_prep(struct dentry *dentry) if (sd->s_type & CONFIGFS_NOT_PINNED) continue; if (sd->s_type & CONFIGFS_USET_DEFAULT) { - mutex_lock(&sd->s_dentry->d_inode->i_mutex); - /* Mark that we've taken i_mutex */ + /* Abort if racing with mkdir() */ + if (sd->s_type & CONFIGFS_USET_IN_MKDIR) { + if (wait_mutex) + *wait_mutex = &sd->s_dentry->d_inode->i_mutex; + return -EAGAIN; + } + /* Mark that we're trying to drop the group */ 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); + ret = configfs_detach_prep(sd->s_dentry, wait_mutex); if (!ret) continue; } else @@ -374,7 +406,7 @@ out: } /* - * Walk the tree, dropping i_mutex wherever CONFIGFS_USET_DROPPING is + * Walk the tree, resetting CONFIGFS_USET_DROPPING wherever it was * set. */ static void configfs_detach_rollback(struct dentry *dentry) @@ -385,11 +417,7 @@ static void configfs_detach_rollback(struct dentry *dentry) list_for_each_entry(sd, &parent_sd->s_children, s_sibling) { if (sd->s_type & CONFIGFS_USET_DEFAULT) { configfs_detach_rollback(sd->s_dentry); - - if (sd->s_type & CONFIGFS_USET_DROPPING) { - sd->s_type &= ~CONFIGFS_USET_DROPPING; - mutex_unlock(&sd->s_dentry->d_inode->i_mutex); - } + sd->s_type &= ~CONFIGFS_USET_DROPPING; } } } @@ -410,7 +438,9 @@ static void detach_attrs(struct config_item * item) list_for_each_entry_safe(sd, tmp, &parent_sd->s_children, s_sibling) { if (!sd->s_element || !(sd->s_type & CONFIGFS_NOT_PINNED)) continue; + spin_lock(&configfs_dirent_lock); list_del_init(&sd->s_sibling); + spin_unlock(&configfs_dirent_lock); configfs_drop_dentry(sd, dentry); configfs_put(sd); } @@ -466,16 +496,12 @@ static void detach_groups(struct config_group *group) child = sd->s_dentry; + mutex_lock(&child->d_inode->i_mutex); + configfs_detach_group(sd->s_element); child->d_inode->i_flags |= S_DEAD; - /* - * From rmdir/unregister, a configfs_detach_prep() pass - * has taken our i_mutex for us. Drop it. - * From mkdir/register cleanup, there is no sem held. - */ - if (sd->s_type & CONFIGFS_USET_DROPPING) - mutex_unlock(&child->d_inode->i_mutex); + mutex_unlock(&child->d_inode->i_mutex); d_delete(child); dput(child); @@ -1001,9 +1027,10 @@ EXPORT_SYMBOL(configfs_undepend_item); static int configfs_mkdir(struct inode *dir, struct dentry *dentry, int mode) { - int ret, module_got = 0; - struct config_group *group; - struct config_item *item; + int ret = 0; + int module_got = 0; + struct config_group *group = NULL; + struct config_item *item = NULL; struct config_item *parent_item; struct configfs_subsystem *subsys; struct configfs_dirent *sd; @@ -1044,28 +1071,32 @@ static int configfs_mkdir(struct inode *dir, struct dentry *dentry, int mode) snprintf(name, dentry->d_name.len + 1, "%s", dentry->d_name.name); mutex_lock(&subsys->su_mutex); - group = NULL; - item = NULL; if (type->ct_group_ops->make_group) { group = type->ct_group_ops->make_group(to_config_group(parent_item), name); - if (group) { + if (!group) + group = ERR_PTR(-ENOMEM); + if (!IS_ERR(group)) { link_group(to_config_group(parent_item), group); item = &group->cg_item; - } + } else + ret = PTR_ERR(group); } else { item = type->ct_group_ops->make_item(to_config_group(parent_item), name); - if (item) + if (!item) + item = ERR_PTR(-ENOMEM); + if (!IS_ERR(item)) link_obj(parent_item, item); + else + ret = PTR_ERR(item); } mutex_unlock(&subsys->su_mutex); kfree(name); - if (!item) { + if (ret) { /* - * If item == NULL, then link_obj() was never called. + * If ret != 0, then link_obj() was never called. * There are no extra references to clean up. */ - ret = -ENOMEM; goto out_put; } @@ -1093,11 +1124,26 @@ static int configfs_mkdir(struct inode *dir, struct dentry *dentry, int mode) */ module_got = 1; + /* + * Make racing rmdir() fail if it did not tag parent with + * CONFIGFS_USET_DROPPING + * Note: if CONFIGFS_USET_DROPPING is already set, attach_group() will + * fail and let rmdir() terminate correctly + */ + spin_lock(&configfs_dirent_lock); + /* This will make configfs_detach_prep() fail */ + sd->s_type |= CONFIGFS_USET_IN_MKDIR; + spin_unlock(&configfs_dirent_lock); + if (group) ret = configfs_attach_group(parent_item, item, dentry); else ret = configfs_attach_item(parent_item, item, dentry); + spin_lock(&configfs_dirent_lock); + sd->s_type &= ~CONFIGFS_USET_IN_MKDIR; + spin_unlock(&configfs_dirent_lock); + out_unlink: if (ret) { /* Tear down everything we built up */ @@ -1161,12 +1207,27 @@ static int configfs_rmdir(struct inode *dir, struct dentry *dentry) return -EINVAL; } - ret = configfs_detach_prep(dentry); - if (ret) { - configfs_detach_rollback(dentry); - config_item_put(parent_item); - return ret; - } + spin_lock(&configfs_dirent_lock); + do { + struct mutex *wait_mutex; + + ret = configfs_detach_prep(dentry, &wait_mutex); + if (ret) { + configfs_detach_rollback(dentry); + spin_unlock(&configfs_dirent_lock); + if (ret != -EAGAIN) { + config_item_put(parent_item); + return ret; + } + + /* Wait until the racing operation terminates */ + mutex_lock(wait_mutex); + mutex_unlock(wait_mutex); + + spin_lock(&configfs_dirent_lock); + } + } while (ret == -EAGAIN); + spin_unlock(&configfs_dirent_lock); /* Get a working ref for the duration of this function */ item = configfs_get_config_item(dentry); @@ -1258,7 +1319,7 @@ static int configfs_dir_open(struct inode *inode, struct file *file) file->private_data = configfs_new_dirent(parent_sd, NULL); mutex_unlock(&dentry->d_inode->i_mutex); - return file->private_data ? 0 : -ENOMEM; + return IS_ERR(file->private_data) ? PTR_ERR(file->private_data) : 0; } @@ -1268,7 +1329,9 @@ static int configfs_dir_close(struct inode *inode, struct file *file) struct configfs_dirent * cursor = file->private_data; mutex_lock(&dentry->d_inode->i_mutex); + spin_lock(&configfs_dirent_lock); list_del_init(&cursor->s_sibling); + spin_unlock(&configfs_dirent_lock); mutex_unlock(&dentry->d_inode->i_mutex); release_configfs_dirent(cursor); @@ -1308,7 +1371,9 @@ static int configfs_readdir(struct file * filp, void * dirent, filldir_t filldir /* fallthrough */ default: if (filp->f_pos == 2) { + spin_lock(&configfs_dirent_lock); list_move(q, &parent_sd->s_children); + spin_unlock(&configfs_dirent_lock); } for (p=q->next; p!= &parent_sd->s_children; p=p->next) { struct configfs_dirent *next; @@ -1331,7 +1396,9 @@ static int configfs_readdir(struct file * filp, void * dirent, filldir_t filldir dt_type(next)) < 0) return 0; + spin_lock(&configfs_dirent_lock); list_move(q, p); + spin_unlock(&configfs_dirent_lock); p = q; filp->f_pos++; } @@ -1362,6 +1429,7 @@ static loff_t configfs_dir_lseek(struct file * file, loff_t offset, int origin) struct list_head *p; loff_t n = file->f_pos - 2; + spin_lock(&configfs_dirent_lock); list_del(&cursor->s_sibling); p = sd->s_children.next; while (n && p != &sd->s_children) { @@ -1373,6 +1441,7 @@ static loff_t configfs_dir_lseek(struct file * file, loff_t offset, int origin) p = p->next; } list_add_tail(&cursor->s_sibling, p); + spin_unlock(&configfs_dirent_lock); } } mutex_unlock(&dentry->d_inode->i_mutex); @@ -1448,9 +1517,11 @@ void configfs_unregister_subsystem(struct configfs_subsystem *subsys) mutex_lock_nested(&configfs_sb->s_root->d_inode->i_mutex, I_MUTEX_PARENT); mutex_lock_nested(&dentry->d_inode->i_mutex, I_MUTEX_CHILD); - if (configfs_detach_prep(dentry)) { + spin_lock(&configfs_dirent_lock); + if (configfs_detach_prep(dentry, NULL)) { printk(KERN_ERR "configfs: Tried to unregister non-empty subsystem!\n"); } + spin_unlock(&configfs_dirent_lock); configfs_detach_group(&group->cg_item); dentry->d_inode->i_flags |= S_DEAD; mutex_unlock(&dentry->d_inode->i_mutex);