Merge branch 'upstream-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jlbec/configfs

* 'upstream-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jlbec/configfs:
  configfs: Rework configfs_depend_item() locking and make lockdep happy
  configfs: Silence lockdep on mkdir() and rmdir()

3 files changed, 178 insertions, 59 deletions

diff --git a/fs/configfs/configfs_internal.h b/fs/configfs/configfs_internal.h
index 762d287123ca..da6061a6df40 100644
--- a/fs/configfs/configfs_internal.h
+++ b/fs/configfs/configfs_internal.h
@@ -39,6 +39,9 @@ struct configfs_dirent {
         umode_t                 s_mode;
         struct dentry           * s_dentry;
         struct iattr            * s_iattr;
+#ifdef CONFIG_LOCKDEP
+        int                     s_depth;
+#endif
 };
 
 #define CONFIGFS_ROOT           0x0001
diff --git a/fs/configfs/dir.c b/fs/configfs/dir.c
index 05373db21a4e..8e48b52205aa 100644
--- a/fs/configfs/dir.c
+++ b/fs/configfs/dir.c
@@ -78,11 +78,97 @@ static const struct dentry_operations configfs_dentry_ops = {
         .d_delete       = configfs_d_delete,
 };
 
+#ifdef CONFIG_LOCKDEP
+
+/*
+ * Helpers to make lockdep happy with our recursive locking of default groups'
+ * inodes (see configfs_attach_group() and configfs_detach_group()).
+ * We put default groups i_mutexes in separate classes according to their depth
+ * from the youngest non-default group ancestor.
+ *
+ * For a non-default group A having default groups A/B, A/C, and A/C/D, default
+ * groups A/B and A/C will have their inode's mutex in class
+ * default_group_class[0], and default group A/C/D will be in
+ * default_group_class[1].
+ *
+ * The lock classes are declared and assigned in inode.c, according to the
+ * s_depth value.
+ * The s_depth value is initialized to -1, adjusted to >= 0 when attaching
+ * default groups, and reset to -1 when all default groups are attached. During
+ * attachment, if configfs_create() sees s_depth > 0, the lock class of the new
+ * inode's mutex is set to default_group_class[s_depth - 1].
+ */
+
+static void configfs_init_dirent_depth(struct configfs_dirent *sd)
+{
+        sd->s_depth = -1;
+}
+
+static void configfs_set_dir_dirent_depth(struct configfs_dirent *parent_sd,
+                                          struct configfs_dirent *sd)
+{
+        int parent_depth = parent_sd->s_depth;
+
+        if (parent_depth >= 0)
+                sd->s_depth = parent_depth + 1;
+}
+
+static void
+configfs_adjust_dir_dirent_depth_before_populate(struct configfs_dirent *sd)
+{
+        /*
+         * item's i_mutex class is already setup, so s_depth is now only
+         * used to set new sub-directories s_depth, which is always done
+         * with item's i_mutex locked.
+         */
+        /*
+         *  sd->s_depth == -1 iff we are a non default group.
+         *  else (we are a default group) sd->s_depth > 0 (see
+         *  create_dir()).
+         */
+        if (sd->s_depth == -1)
+                /*
+                 * We are a non default group and we are going to create
+                 * default groups.
+                 */
+                sd->s_depth = 0;
+}
+
+static void
+configfs_adjust_dir_dirent_depth_after_populate(struct configfs_dirent *sd)
+{
+        /* We will not create default groups anymore. */
+        sd->s_depth = -1;
+}
+
+#else /* CONFIG_LOCKDEP */
+
+static void configfs_init_dirent_depth(struct configfs_dirent *sd)
+{
+}
+
+static void configfs_set_dir_dirent_depth(struct configfs_dirent *parent_sd,
+                                          struct configfs_dirent *sd)
+{
+}
+
+static void
+configfs_adjust_dir_dirent_depth_before_populate(struct configfs_dirent *sd)
+{
+}
+
+static void
+configfs_adjust_dir_dirent_depth_after_populate(struct configfs_dirent *sd)
+{
+}
+
+#endif /* CONFIG_LOCKDEP */
+
 /*
  * 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;
 
@@ -94,6 +180,8 @@ 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) {
                 spin_unlock(&configfs_dirent_lock);
@@ -138,12 +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);
@@ -187,6 +274,7 @@ static int create_dir(struct config_item * k, struct dentry * p,
                 error = configfs_make_dirent(p->d_fsdata, d, k, mode,
                                              CONFIGFS_DIR | CONFIGFS_USET_CREATING);
         if (!error) {
+                configfs_set_dir_dirent_depth(p->d_fsdata, d->d_fsdata);
                 error = configfs_create(d, mode, init_dir);
                 if (!error) {
                         inc_nlink(p->d_inode);
@@ -789,11 +877,13 @@ static int configfs_attach_group(struct config_item *parent_item,
                  * error, as rmdir() would.
                  */
                 mutex_lock_nested(&dentry->d_inode->i_mutex, I_MUTEX_CHILD);
+                configfs_adjust_dir_dirent_depth_before_populate(sd);
                 ret = populate_groups(to_config_group(item));
                 if (ret) {
                         configfs_detach_item(item);
                         dentry->d_inode->i_flags |= S_DEAD;
                 }
+                configfs_adjust_dir_dirent_depth_after_populate(sd);
                 mutex_unlock(&dentry->d_inode->i_mutex);
                 if (ret)
                         d_delete(dentry);
@@ -916,11 +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.
  */
 
 /*
@@ -933,17 +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.
  */
@@ -955,13 +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)
@@ -970,33 +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)
 {
@@ -1037,17 +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);
 
@@ -1072,10 +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);
@@ -1086,7 +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);
 
@@ -1286,13 +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;
@@ -1316,9 +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);
 
@@ -1429,7 +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
diff --git a/fs/configfs/inode.c b/fs/configfs/inode.c
index 5d349d38e056..4921e7426d95 100644
--- a/fs/configfs/inode.c
+++ b/fs/configfs/inode.c
@@ -33,10 +33,15 @@
 #include <linux/backing-dev.h>
 #include <linux/capability.h>
 #include <linux/sched.h>
+#include <linux/lockdep.h>
 
 #include <linux/configfs.h>
 #include "configfs_internal.h"
 
+#ifdef CONFIG_LOCKDEP
+static struct lock_class_key default_group_class[MAX_LOCK_DEPTH];
+#endif
+
 extern struct super_block * configfs_sb;
 
 static const struct address_space_operations configfs_aops = {
@@ -150,6 +155,38 @@ struct inode * configfs_new_inode(mode_t mode, struct configfs_dirent * sd)
         return inode;
 }
 
+#ifdef CONFIG_LOCKDEP
+
+static void configfs_set_inode_lock_class(struct configfs_dirent *sd,
+                                          struct inode *inode)
+{
+        int depth = sd->s_depth;
+
+        if (depth > 0) {
+                if (depth <= ARRAY_SIZE(default_group_class)) {
+                        lockdep_set_class(&inode->i_mutex,
+                                          &default_group_class[depth - 1]);
+                } else {
+                        /*
+                         * In practice the maximum level of locking depth is
+                         * already reached. Just inform about possible reasons.
+                         */
+                        printk(KERN_INFO "configfs: Too many levels of inodes"
+                               " for the locking correctness validator.\n");
+                        printk(KERN_INFO "Spurious warnings may appear.\n");
+                }
+        }
+}
+
+#else /* CONFIG_LOCKDEP */
+
+static void configfs_set_inode_lock_class(struct configfs_dirent *sd,
+                                          struct inode *inode)
+{
+}
+
+#endif /* CONFIG_LOCKDEP */
+
 int configfs_create(struct dentry * dentry, int mode, int (*init)(struct inode *))
 {
         int error = 0;
@@ -162,6 +199,7 @@ int configfs_create(struct dentry * dentry, int mode, int (*init)(struct inode *
                                         struct inode *p_inode = dentry->d_parent->d_inode;
                                         p_inode->i_mtime = p_inode->i_ctime = CURRENT_TIME;
                                 }
+                                configfs_set_inode_lock_class(sd, inode);
                                 goto Proceed;
                         }
                         else